OC-NSString

来源：互联网发布：美的和格力空调知乎编辑：程序博客网时间：2024/06/14 17:29

NSString是不可变字符串

1.初始化

   NSString *string = @"hello";        int number = 3;        NSString *string1 = [[NSString alloc]initWithFormat:@"%@%d",@"hello",number];//可以放多个参数//        NSString *newstring = [NSString stringString:<#(NSString *)#>;        NSString *newstring1 = [NSString stringWithFormat:@"hello"]; //遍历构造器的写法        NSLog(@"string = %@, string1 = %@, newstring1 = %@",string,string1,newstring1);

2.拼接

       //方式1：        NSString *newstring1 = [NSString stringWithFormat:@"hello"];        NSString *string = [newstring1 stringByAppendingFormat:@"world"];        NSLog(@"string = %@,newstring = %@",string,newstring1);        //证明拼接后元字符串是没有改变的        // 方式2：        NSString *string1 = [NSString stringWithFormat:@"%@%@",newstring1,@"world"];        NSLog(@"string = %@, string1 = %@",string,string1);

3.截取

        NSString *string = [NSString stringWithFormat:@"abcdef"];        NSString *newString = [string substringFromIndex:2];//[index , tail]//截取2以及以后的 cdef        NSLog(@"newString = %@",newString);        NSString *newString1 = [string substringToIndex:2];//ab        NSLog(@"newstring1 = %@",newString1);        NSString *newstring = [string substringWithRange:NSMakeRange(1, 2)]; //bc        NSLog(@"newstring1 = %@",newstring);

4.查询

    // 1)查找头部:是否以某个字符串开头        NSString *string = @"www.cctv.com";        //输入网址的时候        BOOL flag = [string hasPrefix:@"www."];        if (flag) {            //找到了操作。。        }else{            //木有找到操作        }                        //2)查找尾部：是否以某个字符串结尾        // 输入邮箱的时候        BOOL flag1 = [string hasSuffix:@".com"];        if (flag1) {            //找到了操作。。        }else{            //木有找到操作        }                //3)查找//        [string rangeOfString:<#(NSString *)#>];//查询一个是否穿是否包含一个字符串        NSRange range = [string rangeOfString:@"cctv"];//cctav        NSLog(@"%ld,%ld",range.location,range.length);//存在的话正确输出,不存在的话range.length= 0                //判断是否有要查找的字符串        if (range.length != 0 && range.location != NSNotFound) {            NSLog(@"找到了");        }else{            NSLog(@"没找到");        }

5.比较

        NSString *string1 = @"121";        NSString *string2 = @"122";        NSComparisonResult result = [string1 compare:string2];//相同返回0，上面比下面长返回1，下面长返回-1        NSLog(@"%ld",result);        //NSOrderedAscending  -1 升序        //NSOrderedSame        0 相等        //NSOrderedDescending  1 降序        if (result == NSOrderedSame) {            NSLog(@"相等");        }//        //数值类型转化为字符串//        int number1 = [string1 intValue];//        int number2 = [string2 intValue];                //内容比较        if ([string1 isEqualToString:string2]) {            NSLog(@"内容相同");        }

6.大小写转化，数值转化

  NSString *string = @"hEllo WoRld";        NSString *newstring = [string uppercaseString];//转换为大写uppercaseString        NSLog(@"%@",newstring);        NSString *newstring1 = [string lowercaseString];//转换为小写lowercaseString        NSLog(@"%@",newstring1);

7.长度

8.替换

        NSString *string = @"hello world hello";        NSString *newstring = [string stringByReplacingOccurrencesOfString:@"hello" withString:@"abc"];//参数2替换参数1        NSLog(@"newString = %@",newstring);

9.获取字符

        NSString *string = @"hello world hello";        char ch = [string characterAtIndex:1];        NSLog(@"%c",ch);

0 0