```
NSString * string = @“11111111111”;
NSString * str1 = [string substringToIndex:3];
NSLog(@"%@",str1);
专门截取字符串的一块从第3位开始，长度为4
NSString * str2 = [string substringWithRange:NSMakeRange(3, 4)];
NSLog(@"%@",str2);
从第七位开始带结束
NSString * str3 = [string substringFromIndex:7];
NSLog(@"%@",str3);
string = [NSString stringWithFormat:@"%@-%@-%@",str1,str2,str3];
NSString *tempA = @"123";
NSString *tempB = @"456";
1，字符串拼接
NSString *newString = [NSString stringWithFormat:@"%@%@",tempA,tempB];
2，字符转int
int intString = [newString intValue];
3，int转字符
NSString *stringInt = [NSString stringWithFormat:@"%d",intString];
4，字符转float
float floatString = [newString floatValue];
5，float转字符
NSString *stringFloat = [NSString stringWithFormat:@"%f",intString];
将string字符串转换为array数组
NSArray *array = [Str componentsSeparatedByString:@","];
＝＝反向方法
将array数组转换为string字符串
NSString *tempString = [mutableArray componentsJoinedByString:@","];--分隔符
判断字符串是否包含字符
BOOL is = [string containsString:@"%2520"];
/// 替换字符，将字符串中的部分数据换成另一个
/// @param string 要修改的字符串
/// @param num 替换的起始位置
/// @param end 替换的长度
-(NSString *)string:(NSMutableString *)string start:(NSInteger)num end:(NSInteger)end{
NSRangerange =NSMakeRange(num, end);
NSString* str2 =@"";
for(inti =0; i < end; i++) {
str2 = [NSStringstringWithFormat:@"%@*",str2];
}
[stringreplaceCharactersInRange:range withString:str2];
returnstring;
}
```
