《Ruby基础教程》第三部分提取笔记

第三部分

数值类

  1. 一些方法：

    • 返回商的整数：x.quo(y)

    • 返回一个数组，[商，余数]：x.divmod(y)

    • Math模块 你想得到的数学函数都在里面

    • 返回整数部分：.floor

    • 返回100以内的随机数：Random.rand(100) （比我以前学的VB方便太多了好嘛！）

    • Integer的迭代方法：

      • upto遍历

      • downto遍历

    • 以分数的形式存在：Rational(1, 10)

    • 按step迭代的方法：

      • 2到10，每次加3：

        <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n518" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
        2.step(10,3) do |i|
        p i
        end #=> 2, 5, 8</pre>

      • 10到2，每次减3：

        <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n522" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
        10.step(2,-3) do |i|
        p i
        end #=> 10, 7, 4</pre>

数组：

  1. Array.new方法：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n528" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    Array.new #=> []
    Array.new(5) #=> [nil,nil,nil,nil,nil]
    Array.new(5,0) #=> [0,0,0,0,0]</pre>

  2. %w和%i

    • 创建不包含空白的字符串数组时，可以使用%w:

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n536" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      lang = %w(Ruyb Perl Python Scheme Pike)
      p lang #=>["Ruby","Perl","Python","Scheme","Pike"]</pre>

    • 创建不包含空白的符号数组时，可以使用%i:

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n540" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      lang = %w(Ruyb Perl Python Scheme Pike)
      p lang #=>[:Ruby,:Perl,:Python,:Scheme,:Pike]</pre>

    其中()可替换成其他符号：<> || !! @@ AA

  3. 将散列转换成数组：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n546" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = {a: 1, b: 2}
    a.to_a #=> [[:a, 1], [:b, 2]]</pre>

  4. 一次性拿到多个值：

    • a[n] or a[-n] 如果是负数，就倒着开始取值。超过总数值会报错。

  • a[n..m] or a[n…m]

    • a[n,len] 从某个元素起，取n个字符。

  1. 一次性赋多个值：

    • <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n569" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = [1,2,3,4,5,6]
      a[2,3] = [c,d,e] #=> [1,2,c,d,e,6]
      a[2,0] = [a,b] #=> [1,2,a,b,3,4,5,6]</pre>

    • <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n571" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = [1,2,3,4,5,6]
      a[2..3] = [a,b] #=> [1,2,a,b,5,6]</pre>

    • .values_at方法：

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n575" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = [1,2,3,4,5,6]
      a.values_at(1,3,5) #=> [2,4,6]</pre>

  2. 把数组当集合来运算：

    • 交集：ary = ary1 & ary2

    • 并集：ary = ary1 | ary2

    • 集合的差：ary = ary1 - ary2 （在1中找2没有的元素）

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n589" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      ary1 = ["a","b","c"]
      ary2 = ["b","c","d"]
      p (ary1 - ary2) #=> ["a"]</pre>

  3. 把数组当<u style="box-sizing: border-box;"><u style="box-sizing: border-box;">列</u></u>：

    数组结构：

    • 队列：以排列的顺序，先进先出。（像排队过关一样）
    • 栈：以相反的顺序，先进后出。（像堆东西一样，最慢放入的最容易取出）
    • 追加，删除，引用：

    <figure class="md-table-fig" contenteditable="false" cid="n607" mdtype="table" style="box-sizing: border-box; margin: -8px 0px 0px -8px; overflow-x: auto; max-width: calc(100% + 16px); padding: 8px;">

    操作 在头部开刀 在尾部开刀
    追加元素 unshift push
    删除元素 shift pop
    引用元素 first last

    </figure>

    例子：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n626" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = [1,2,3,4,5]
    a.push("E") #=> [1,2,3,4,5,E]
    a.shift #=> 1
    a #=> [2,3,4,5,E]</pre>

一些操作方法：

  1. 为数组增加元素：

    • a.unshift(item)

    • a.push(item) ~= a << item

    • a.concat(b) & a+b

      这个concat方法是破坏性方法，会改变被引用的对象。

    什么是<u style="box-sizing: border-box;"><u style="box-sizing: border-box;">破坏性的方法</u></u>？

    ：会改变接收对象值的方法！要注意：被引用的对象也会被破坏！如：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n651" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = [1,2,3,4]
    b = a
    b.pop #=> 4
    p a #=> [1,2,3]</pre>

    提示：这里b引用了a，并不是复制一个a，而是让a和b同时引用一个对象！这一点要纠正认识！

  2. 从数组中删除元素：

    • a.compact & a.compact! ：会把a数组中的空元素nil去掉！区别：

      • 第一种会返回一个新的数组。

      • 第二种会直接替换掉原来的数组。

    • a.delete(x) ：从数组中删除x元素。

    • a.delete_at(n) : 从数组中删除a[n]元素。

    • a.delete_if {|item| … }``a.reject {|item| … }``a.reject! {|item| … }: 这三个方法表示：遍历所有元素，如何右边的block块成立就删掉，其中带感叹号表示破坏性的方法！

    • a.slice!(n)``a.slice!(n..m)``a.slice!K(n,len): 这三个方法表示：从数组a中删除指定的部分，并返回被删除的部分的值。slice!是具有破坏性的方法。

    • a.uniq & a.uniq! ：表示：去掉重复的元素。

    • a.shift ：删除开头的元素。返回删除的值。

    • a.pop ：删除末尾的元素。返回删除的值。

  3. 替换数组元素：

    • a.collect{|item| … }``a.collect!{|item| … }``a.map{|item| … }``a.map!{|item| … }: 遍历数组a和各元素传给block中的item,最后付出处理后的结果。

    • a.fill(value)``a.fill(value, begin)``a.fill(value, begin, len)``a.fill(value, n..m)： 把数组指定元素全部替换成value，默认为全部。

    • a.flatten & a.flatten! ：平坦化数组a，就是把里面嵌套的数组展开成一个大数组。(soga，原来是这样啊！)

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n716" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = [1,[2,[3]],[4],5]
      a.flatten!
      p a #=> [1,2,3,4,5]</pre>

    • a.reverse & a.reverse! :反转数组a的元素顺序。

    • a.sort``a.sort!``a.sort {|i,j| … }``a.sort {|i,j| … }：排序，其中block中的i & j 表示：从数组中两个两个拿出来的数据。

    • a.sort_by{|i| … } ：根据块的运行结果时序排序。

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n730" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = [2,4,3,5,1]
      p a.sort_by{|i| -i } #=> [5,4,3,2,1] (这里的block只是参与计算而已，不会破坏原来的数组。)</pre>

  4. 数组与迭代器：有些使用迭代器的对象不是数组，但处理后会返回一个数组:

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n734" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = 1..5
    b = a.collect{|i| i += 2}
    p b #=> [3,4,5,6,7]</pre>

  5. 数组的初始化问题：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n738" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = Array.new(3, [0,0,0]) #=> [[0,0,0],[0,0,0],[0,0,0]]
    a[0][1] = 2 #=> [[0,2,0],[0,2,0],[0,2,0]]
    数组的初始化就是有这些问题，要注意，可以使用block带解决：
    a = Array.new(3) {[0,0,0])} #=> [[0,0,0],[0,0,0],[0,0,0]]
    a[0][1] = 2 #=> [[0,2,0],[0,0,0],[0,0,0]]</pre>

  6. zip方法 ：引进多个数组，然后同步遍历！：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n742" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    ary1 = [1,2,3,4,5]
    ary2 = [10,20,30,40,50]
    ary3 = [100,200,300,400,500]
    ​
    result = []
    ary1.zip(ary2,ary3) do |a, b, c|
    result << a + b + c
    end
    p result #=> [111, 222, 333, 444, 555]</pre>

  7. 一个过滤数组的方法：.select

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n746" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = (1..100).to_a
    a.select{|i| i % 3 == 0} 过滤3的倍数。</pre>

    ​

13章练习题：

  1. 创建一个1到100的整数按升序排列的数组：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n754" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    (1..100).to_a</pre>

  2. 累加1中的数组：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n758" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a.reduce :+</pre>

  3. inject方法：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n762" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a.inject(0){|memo, i| memo += i}
    表示：遍历数组元素赋值给i，每次结果回传给memo.实现累加的效果。</pre>

字符串String

  1. 什么是内嵌表达式？

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n770" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    "String#{ruby}" #=> 这个#{}里可以执行ruby表达式的东西就是啦！</pre>

  2. 创建字符串

    • 使用%Q与%q

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n778" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      desc = %Q{Ruby 的字符中也可以使用'' 和 "".}
      str = %q|Ruby said, 'Hello world!'|
      ​
      其中%Q相当于"",%q相当于''。</pre>

    • Here Document方法

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n782" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      <<"结束标识"
      内容
      结束标识
      ​

      => (这里更多的时候要换成<<-"结束标识"，这样能让结束的标识不一定在)

      ​
      这个方法应该很少用。</pre>

    • sprintf方法 & printf方法

      • printf

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n790" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      n = 123
      printf("%d\n", n) #=> %d表示以整数形式输出
      printf("%4d\n", n) #=> %4d表示以4位数格式输出
      printf("%04d\n", n) #=> %04d表示不够4位时被零
      printf("%+d\n", n) #=> %+d表示输出结果带 + or -</pre>

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n791" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      n = "Ruby"
      printf("Hello,%s!\n",n) #=> %s表示以字符串形式输出
      printf("Hello,%8s!\n",n) #=> %8s表示输出炎8位字符串
      printf("Hello,%-8s!\n",n) #=> %-8s表示输出左对齐的8位字符</pre>

      • sprintf

      和printf一样的结果。但书中没有说明具体区别，差评！

  3. 获取字符串的长度

    • length or size两种方法可以，随意！

    • bytesize可以获取字节数。

    • 判断是否为0：empty?

  4. 字符串的索引

    • 当成数组一样用就可以了。

  5. 连接字符串

    • 用 + 号

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n825" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = "Hello,"
      b = "World!"
      a + b #=> "Hello,World!"</pre>

    • 用 << 号

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n829" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = "Hello,"
      b = "World!"
      a << b #=> "Hello,World!" (a会被改变！)</pre>

  6. 字符串的比较

    • 判断两个字符串是否相同：== !=

    • 比较大小

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n840" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      "aaaaa" < "b" #=> true 一般按照a~z的顺序排序</pre>

    • 如果查看码位 : .ord

  7. 字符串的分割：split(x) ：以x为分割点进行分割！

  8. 换行符的操作：

    • 删掉

      <figure class="md-table-fig" contenteditable="false" cid="n854" mdtype="table" style="box-sizing: border-box; margin: -8px 0px 0px -8px; overflow-x: auto; max-width: calc(100% + 16px); padding: 8px;">

      属性 删掉最的一个字符 删掉挑选符
      非破坏性的 chop chomp
      破坏性的 chop! chomp!

      </figure>

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n867" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = "abcde"
      b = "abcde\n"
      a.chop #=> "abcd"
      b.chop #=> "abcde"
      b.chomp #=> "abcde"</pre>

  9. 字符串的检索与置换

    • 字符串的检索

      • index方法 从左到右检索，返回第一个字母的索引

      • rindex方法 从右到左检索，返回第一字母的索引

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n882" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = "abbbbbb"
      a.index("bb") #=> 1
      a.rindex("bb") #=> 5</pre>

    • 判断是否包含某个索引值: include?

      <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n886" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
      a = "abbbbbb"
      a.include?("bb") #=> true</pre>

  10. 字符串与数组有很多共同的索引的方法：

  • s[n] s[n..m] s.slice!(n)

  • s.concat(s2) s+s2 s.delete(str) s.reverse

  1. 其他方法：
*   `strip` : 删除头尾的空白字符

*   `upcase` ：小写转大写

*   `downcase` ：大写转小写

*   `swapcase` ：大的转小，小的转大

*   `capitalize` ：首字母大写，其余转小写

*   `tr` ：置换字符，与`gsub`相似，但这里可以一次转换多个字符。

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n920" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, &quot;Liberation Mono&quot;, Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    "ABCDE".tr("BD", "bd")    #=> "AbCdE"</pre>
14章节练习题提取：

  1. 一个打散的字符串数组，如何快速连接成句子：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n927" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = ["Ruby", "is", "an", "object", "oriented", "programming", "language"]
    a.join(" ")

    => "Ruby is an object oriented programming language"</pre>

  2. 统计下面各个字母出现次数，并用*的个数来表示次数：

    <pre class="md-fences md-end-block" lang="" contenteditable="false" cid="n931" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 0.9em; white-space: pre; text-align: left; break-inside: avoid; display: block; background-image: inherit; background-size: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(221, 221, 221); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; padding: 8px 1em 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; caret-color: rgb(51, 51, 51); color: rgb(51, 51, 51); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none; background-position: inherit inherit; background-repeat: inherit inherit;">
    a = "Ruby is an object oriented programming language"
    b = Hash.new(0)
    a.each_char do |c|
    b[c] += 1
    end
    b.sort.each do |k, v|
    printf("'%s': %s\n", c, "*" * v.to_i)
    end</pre>

    运行结果如图：

    image

    很酷！

    • 散列直接用a[c]就可以拿到这个值，不需要进行检索

    • printf格式输出，方便！先定义好整个字符串样式，再后面定义各个引用值。

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