OC系列foundation Kit基础－NSString

一.NSString常见创建

1.声明一个常量字符串

NSString *str = @"abc";

2.通过构造方法创建字符串

NSString *str1 = [[NSString alloc]initWithString:@"abc"];
NSString *str2 = [[NSString alloc]initWithUTF8String:"abc"];
NSString *str3 = [[NSStringalloc]initWithFormat:@"%@%c",@"ab",'c'];

3.通过类方法创建字符串

NSString *str1 = [NSString stringWithString:@"abc"];
NSString *str2 = [NSString stringWithUTF8String:"abc"];
NSString *str3 = [NSString stringWithFormat:@"%@%c",@"ab",'c'];

二.字符串比较

1.判断两个字符串是否相等(isEqualToString)

NSString *str1 = @"1234567890";
NSString *str2 = @"1234567890";
BOOL ret = [str1 isEqualToString:str2];
NSLog(@"ret is %d",ret);

输出结果:

2016-06-27 10:56:56.284 OcTest[561:282681] ret is 1
Program ended with exit code: 0

2.两个字符串比较函数(compare)

        NSString *str1 = @"1234567890";
        NSString *str2 = @"12345";
        
        NSComparisonResult result = [str1 compare:str2];
        
        if (result == NSOrderedAscending)
        {
            NSLog(@"str1 < str2");
        }
        else if (result == NSOrderedDescending)
        {
             NSLog(@"str1 > str2");
        }
        else if (result == NSOrderedSame)
        {
             NSLog(@"str1 = str2");
        }

　　输出结果:

2016-06-27 11:03:48.707 OcTest[597:310397] str1 > str2
Program ended with exit code: 0

三.字符串截取

首先创建一个字符串，下面以str1为例:

 NSString *str1 = @"1234567890";

1.截取到第六位(substringToIndex)

NSString *str = [str1 substringToIndex:6];
NSLog(@"str is %@",str);

　　输出结果:

2016-06-27 11:12:11.284 OcTest[637:341212] str is 123456
Program ended with exit code: 0

2.从第六位开始截取(substringFromIndex)

NSString *str = [str1 substringFromIndex:6];
NSLog(@"str is %@",str);

　　输出结果:

2016-06-27 11:15:12.630 OcTest[664:356189] str is 7890
Program ended with exit code: 0

3.字符串范围截取(substringWithRange)

NSString *str = [str1 substringWithRange:NSMakeRange(0, 5)];
NSLog(@"str is %@",str);

　　输出结果:

2016-06-27 11:17:38.833 OcTest[674:366407] str is 12345
Program ended with exit code: 0

四.一个字符串在另一个字符串中的位置(rangeOfString)

首先新创建一个字符串str2

NSString *str2 = @"1234";

NSRange range = [str1 rangeOfString:str2];
NSLog(@"range loc is %zd,range length is %zd",range.location,range.length);

　　输出结果:

2016-06-27 11:24:01.916 OcTest[684:394116] range loc is 0,range length is 4
Program ended with exit code: 0

五.字符串查询

        NSString *str = @"f232423dsgerh23wd3349k00cv3";
        NSScanner *scanner = [NSScanner scannerWithString:str];
        while(![scanner isAtEnd] && ++scanner.scanLocation){
            int result;
            if([scanner scanInt:&result]){
                NSLog(@"%d",result);
            }
        }

　　输出结果：

2016-07-01 15:10:15.231 OCString[851:320391] 232423
2016-07-01 15:10:15.232 OCString[851:320391] 23
2016-07-01 15:10:15.232 OCString[851:320391] 3349
2016-07-01 15:10:15.232 OCString[851:320391] 0
2016-07-01 15:10:15.232 OCString[851:320391] 3
Program ended with exit code: 0