NSString [a compare:b] NSOrderedSame NSOrderedAscending NSOrderedDesc

转载自：http://blog.sina.com.cn/s/blog_8345c9c90100vevx.html

NSString 两个字符串的比较，用 a compare:b 来比，得出的结果分3种  

1. 26个字母比较  越靠后面  越大

    NSString *a = @"qweqwe";

    NSString *b = @"qweasd";

    BOOL result = [a compare:b];

    if (result == NSOrderedSame) {          // NSOrderedSame = 0 完全一样

        NSLog(@"a = b");

    }else if(result == NSOrderedAscending)  // NSOrderedAscending = -1

        NSLog(@"a < b");

    else{                                   //NSOrderedDescending = +1

        NSLog(@"a > b");

    }

 

    2011-07-05 15:04:33.951 Q[5180:207] a > b

2.比较数字或者符号，或者字母 什么都行

 

   NSString *a = @"1.0.30qweqwe";

    NSString *b = @"1.0.45qweasd";

    BOOL result = [a compare:b];

    if (result == NSOrderedSame) {          // NSOrderedSame = 0 完全一样

        NSLog(@"a = b");

    }else if(result == NSOrderedAscending)  // NSOrderedAscending = -1

        NSLog(@"a < b");

    else{                                   //NSOrderedDescending = +1

        NSLog(@"a > b");

    }

 

  2011-07-05 15:05:13.175 Q[5209:207] a < b

3.不考虑大小写比较字符串 

[a caseInsensitiveCompare:b]

 

 

 

- (void)viewDidLoad

{

    NSString *a = @"i love my boyfriend.";

    NSString *b = @"I Love My Boyfriend.";

    NSLog(@" \n a:  %@ \n",a);

    NSLog(@" \n b:  %@ \n",a);

    BOOL result = [a caseInsensitiveCompare:b] ==  NSOrderedSame;

｝

// result = (BOOL) YES;

4.不考虑大小写比较字符串 

[a caseInsensitiveCompare:b]

 

- (void)viewDidLoad

{

    NSString *a = @"i love my boyfriend.";

    NSString *b = @"Little baby.";

    NSLog(@" \n a:  %@ \n",a);

    NSLog(@" \n b:  %@ \n",a);

    BOOL result = [a caseInsensitiveCompare:b] ==  NSOrderedAscending;

}

//result = (BOOL) YES;

5. 有选择的比较大小   [a compare:b options:NSCaseInsensitiveSearch|NSNumericSearch]

- (void)viewDidLoad

{

    NSString *a = @"i love my boyfriend.";

    NSString *b = @"I Love My Boyfriend.";

    NSLog(@" \n a:  %@ \n",a);

    NSLog(@" \n b:  %@ \n",b);

    BOOL result = [a compare:b options:NSCaseInsensitiveSearch|NSNumericSearch] ==  NSOrderedSame;

}

//result = (BOOL)YES;

NSCaseInsensitiveSearch  忽略大小写的比较字符串

NSNumericSearch       比较字符串的个数

NSLiteralSearch       区分大小写，进行完全比较