NSMultableString

NSMutableString *str=[NSMutableString stringWithCapacity:0];


@增

[str appendString:@"123"];

[str appendFormat:@"%d",11];

[str insertString:@"45" atIndex:3];



@删（删的还是自己）

//删除可变字符串中的一个区间的字符串
[str deleteCharactersInRange:NSMakeRange(3, 2)];



@改

//把可变字符串的一段改为第二个参数的字符串内容 

[str replaceCharactersInRange:NSMakeRange(3, 2) withString:@"45"];


//全改

[str setString:@"54321"];



@拼

NSString * str = @"I am so bad man";

NSArray * array = [str componentsSeparatedByString:@" "];//分割字符串

NSMutableArray * mutableArray = [[NSMutableArray alloc] init];

NSEnumerator * enumerator = [array objectEnumerator];

NSString * obj;

while (obj = [enumerator nextObject]) {

    [mutableArray addObject:obj];

}

NSString * newStr = [mutableArray componentsJoinedByString:@"，"];//拼接字符串

NSLog(@"%@",newStr);