构建方法
str = 'hello world' # 只允许`\\`与`\'`转义
str = "hello world" # 允许所有转义和`#{}`字符串拼接
str = %q/hello world/ # 等同单引号
str = %Q{hello world} # 等同双引号
str=<<EOS
hello world
EOS
str = "abc" * 2 # => "abcabc"
索引
str = "abc"
s = str[-1] # s => 'c'
s1 = str[2] # s1 => 'c' ，ruby中的字符视为整数
s2 = str[1,2] # s2 => "bc" ，表示从1下标开始去长度2的两个字符
s3 = str[1..2] # s3 => "bc" ，下标从1取到2
操作方法
给定字符串str = "abc"
空字符吗
str.empty? # => false
长度
str.length # => 3
str.size # => 3
删除换行符
str.chop # => "ab" 无条件切除最后一个字符
str.chomp # => "abc" 若行末为换行符则删除
str1 = "abc\n"
str1.chomp # => "abc"
str1.chop # => "abc"
# 破坏性删除使用，str1.chomp! str1.chop!，即引用删除并返回
删除前后空白
str1 = " abc "
str1.strip # => "abc"
找指定字符串索引
str.index(a) # => 0，从左向右索引，索引从0开始
str.rindex(a) # => 3 ，从右向左索引，索引从1开始
包含指定子串吗
str.include? "ab" # => true
指定位置插入
str.insert(1,"dd") # => "addbc", 1下标字符前插入
str.insert(-1."dd") # => "abcdd", 倒数第n字符后插入
替换
##
# 用法
# str.gsub(pattern, replacement) => new_str
# str.gsub(pattern) {|match| block } => new_str
##
str.gsub(/[aeiou]/, '*') # => "*bc" #将元音替换成*号
str.gsub(/([aeiou])/, '<\1>') # => "<a>bc" 将元音加上尖括号,\1表示匹配字符
str.gsub(/[aeiou]/) {|s| s + ' '} #=> "104 101 108 108 111 "
str.replace "abca" # str => "abca"，重定义字符串
# 单次替换，用法与gsub相同，但仅替换第一次匹配
str1 = "aaaa"
str1.sub(/[aeiou]/,'d') # => "daaa"
删除
# 查询删除
str.delete "b" # => "ac",参数为字符串
# 索引方式删除
str.slice!(-1) == str.slice!(2) # => true
s = str.slice!(1,2) # s=> "a", 用法 => str.slice(index,len)
s1 = str.slice!(1..2) # s1 => "a", 用法 => str.slice!(index_begin..index_end)
分割为数组
str1 = "11:22:33:44"
column = str1.split(/:/) # column=> ["11", "22", "33", "44"]
翻转
str.reverse # => "cba"
大小写转换
str1 = str.upcase # str1 => "ABC"
str1.downcase # => "abc"
str.swapcase # => "ABC" 大写变小写，小写变大写
str.capitalize # => "Abc" 首字母大写，其余小写
