NSString

/***********************NSString***********************/#pragma mark 获取字符串长度 string.length    NSString *string = @"12345678";    NSLog(@"%ld",string.length);#pragma mark 获取子字符串，调用系统方法 substringFromIndex:    NSString *string = @"www.lanou.com";       NSString *str1 =  [string substringFromIndex:4];       NSLog(@"%@",str1);   #pragma mark 截取指定范围的字符串 substringWithRange:    //NSRange表示范围的结构体    NSRange a = {4,5};    NSString *str3 = [string substringWithRange:a];       NSLog(@"%@",str3);   #pragma mark 拼接字符串 stringByAppendingString:    NSString *string = @"I love";    NSString *string1 = @" Kitty";       //appand是拼接的意思    NSString *string2 =  [string stringByAppendingString:string1];    NSLog(@"%@",string2);         #pragma mark 替换字符串 stringByReplacingOccurrencesOfString:@"I" withString:    NSString *string = @"I love You";    NSString *string1 = @" Kitty";    NSString *string2 =    [string stringByReplacingOccurrencesOfString:@"I" withString:@"You"];    NSLog(@"%@",string2);      #pragma mark 判断字符串是否相等 isEqualToString:    NSString *string = @"abcd";    NSString *string1 = @"abc";    if ([string isEqualToString:string1]) {        NSLog(@"字符串相等");    }else    {        NSLog(@"字符串不相等");    }         #pragma mark 字符串是否一一个字符开头 hasPrefix:    NSString *string = @"abcdefg";    if ([string hasPrefix:@"a"]) {        NSLog(@"字符串以a开头");    }else    {        NSLog(@"字符串不以a开头");    }   #pragma mark 字符串是否一一个字符结尾 hasSuffix:      if ([string hasSuffix:@"efg"]) {        NSLog(@"是以efg结尾");    }else    {        NSLog(@"不是以efg结尾");    }       给定一个图片文件名，判断字符串中是否以“png”结尾，如果是就替换成“jpg”如果不是，就拼接“.jpg”    NSString *string = @"abc.png";       if ([string hasSuffix:@"png"]) {        string = [string stringByReplacingOccurrencesOfString:@"png" withString:@"jpg"];    } else {         string =  [string stringByAppendingString:@".jpg"];    }          NSLog(@"%@",string);/***********************NSString************************//***********************NSMutableString******************/#pragma mark - 可变字符串    //可变字符串本身是可以修改的    NSMutableString *mutString = [NSMutableString stringWithFormat:@"张三"];#pragma mark 插入字符串 insertString: atIndex:    [mutString insertString:@"大" atIndex:1];    NSLog(@"mutString = %@",mutString);#pragma mark 删除字符串 deleteCharactersInRange:    NSRange a = {1,2};    [mutString deleteCharactersInRange:a];    NSLog(@"mutString = %@",mutString);   #pragma mark 拼接 appendString:    NSMutableString *mutString = [NSMutableString stringWithFormat:@"张三"];    [mutString appendString:@"好"];    NSLog(@"mutString = %@",mutString);   /***********************NSMutableString******************/