字符串NSString

一.创建字符串(各种方法)

//1.最简单的创建方法

        NSString *str1 = @"hello world !";//str1指向常量区
        str1 = @"哈哈";//str1(指针)的重指向
        NSLog(@"%@",str1);

 //2.废柴写法

        NSString *str2 = [[NSString alloc]initWithString:@"aa"];

    //str2仍然指向常量区

 //3.最正宗的写法(指向堆区)

        NSString *str3 = [[NSString alloc]initWithFormat:@"%@ %@",str2, str1];
        NSString *str4 = [[NSString alloc]initWithFormat:@"%@",@"我是小四"];
        NSLog(@"%@",str3);
        NSLog(@"%@",str4);

**************2.字符串长度***************
//length计算字符串的长度 返回值是NSUIntger

        NSString *str5 = @"dsgtretre";
        NSUInteger len = str5.length;//[str5 length]==str5.length
        NSLog(@"字符串长度为%lu",len);

**************3.获取字符串前缀、后缀***************
//关键字1:prefix判断前缀 返回值BOOL类型

NSString *str6 = [[NSString alloc]initWithFormat:@"http://www.baidu.com"];
BOOL isPrefix = [str6 hasPrefix:@"http"];
        NSLog(@"isPrefix = %d",isPrefix);
        BOOL isSuffix = [str6 hasSuffix:@".com"];
        NSLog(@"isSuffix = %d",isSuffix);
        NSLog(isPrefix && isSuffix ? @"此链接是正确的" : @"此链接不正确");

**************4.查找字符串的范围***************

NSString *str7 = [[NSString alloc] initWithFormat:@"you are beautiful"];

    //判断str7中是否含有are这个字符串
    //新的数据类型:NSRange结构体类型(两个成员变量);location字符串开始的位置  length字符串的长度

//一旦子串不存在母串中,输出location就会输出一个随机值

        NSRange range = [str7 rangeOfString:@"are"];        NSLog(@"location=%ld,length=%ld",range.location,range.length);
        NSLog(range.length == 0 ? @"查找失败" : @"查找成功");

**************5.获取子字符串***************

//有三种方法,关键字sub,to,from
        NSString *str8 = @"nizhenbang";
        //1.给定字符串开始的位置,截取到最后一个字符
        //sub--子 super--父
        NSString *subStr1 = [str8 substringFromIndex:6];
        NSLog(@"subStr1=%@",subStr1);
        //2.关键字to,给定结束位置,从第一个字符串开始截取,到指定字符串结束(不包含指定位置上的字符串)
        NSString *subStr2 = [str8 substringToIndex:6];
        NSLog(@"subStr2=%@",subStr2);
        //3.关键字range 任意位置截取任意长度的子串
        //先创建range变量,指定要截取额范围
        NSRange range1 = [str8 rangeOfString:@"zhen"];
        NSString *subStr3 = [str8 substringWithRange:range1];
        NSLog(@"subStr3=%@",subStr3);
        
        //第二种方式,不提前设置range变量
        NSString *subStr4 = [str8 substringWithRange:NSMakeRange(3, 4)];
        //NSMakeRange用来设置NSRange变量(注意非对象类型不要带*)
        NSLog(@"subStr4=%@",subStr4);

**************6.字符串拼接***************

//关键字:appending
        NSString *str9 = [NSString stringWithFormat:@"HaoRan"];
        //在str9后面拼接" is a handsome boy"
        NSString *newStr = [str9 stringByAppendingString:@" is a handsome boy"];
        NSLog(@"newStr=%@",newStr);

**************7.字符串替换***************

NSString *s1 = [NSString stringWithFormat:@"ihello hello hi hi"];
        //1.用指定字符串替换指定内容,比如将hello替换成haha,全部hello都被替换成haha
        NSString *newStr1 = [s1 stringByReplacingOccurrencesOfString:@"hello" withString:@"haha"];
        NSLog(@"newStr1=%@",newStr1);
        //2.指定替换长度,比如将第一个hi改成yes
        NSString *newStr2 = [s1 stringByReplacingCharactersInRange:NSMakeRange(16, 2) withString:@" yes"];
        NSLog(@"newStr2=%@",newStr2);

**************8.字符串大小写转换***************

NSString *s2 = [NSString stringWithFormat:@"rgreg dxg dgde"];
        //1.全部转为大写
        NSString *upperStr = [s2 uppercaseString];
        NSLog(@"upperStr=%@",upperStr);
        //2.全部小写
        NSString *lowerStr = [upperStr lowercaseString];
        NSLog(@"lowerStr=%@",lowerStr);
        //3.首字母转为大写 capital
        NSString *captilStr = [lowerStr capitalizedString];
        NSLog(@"captilStr=%@",captilStr);

**************9.字符串比较***************

NSString *s3 = @"bcc";
        NSString *s4 = @"bbb";
        //比较关键字:compare
        NSComparisonResult result = [s3 compare:s4];
        //NSComparisonResult本质就是NSInteger整型数据.被定义出来只是为了接受对象的比较结果.结果有三种类型 -1(升序,前小后大) 0(值相等) 1(降序,前大后小)
        NSLog(@"%ld",result);