iOS-NSComparisonResult和NSComparator介绍,比较,排序

什么是NSComparisonResult和NSComparator???

官方文档:https://developer.apple.com

typedef NS_ENUM(NSInteger, NSComparisonResult) 

     {

     NSOrderedAscending = -1L, //值为－1 代表升序排列

     NSOrderedSame,            //值为0

     NSOrderedDescending       //值为1   待变降序排列

     };

     

     基础类库中声明了NSComparator块代码类型来进行两个条目的比较：

     typedef NSComparisonResult (^NSComparator)(id obj1, id obj2);

     NSComparator是一个块代码类型，并且使用两个对象作为参数，返回一个NSComparisonResult类型的值。它是NSSortDescriptor,NSArray, 和NSDictionary等类的方法的参数，用来进行排序.

比较

    NSString *a = @"aaaA";//'A'的ASCII码值是65
    NSString *b = @"aaaa";//'a'的ASCII码值是97
    NSComparisonResult comparisonResult = [a compare:b];
    if (comparisonResult == NSOrderedAscending) {
        NSLog(@"b > a");
    }
    else if (comparisonResult == NSOrderedDescending)
    {
        NSLog(@"a > b");
    }
    else if (comparisonResult == NSOrderedSame)
    {
        NSLog(@"a = b");
    }
    
    NSLog(@"comparisonResult = %ld",comparisonResult);

    //输出结果为－1，即：NSOrderedAscending。

    //表示在两个字符串不相同，且第一个字符所在的字符串a比b的ASCII码值要小。

    //比较
    NSNumber *num1 = [[NSNumber alloc]initWithFloat:15.5];
    NSNumber *num2 = [[NSNumber alloc]initWithFloat:15.5];
    
    NSComparisonResult result = [num1 compare:num2];
    if (result == NSOrderedSame) {
        NSLog(@"a");
    }
    NSLog(@"result = %ld",result);

排序(升序)

    NSArray *stringArray = [NSArray arrayWithObjects:@"abc 1", @"abc 21", @"abc 12",@"abc 13",@"abc 05",nil];
    NSComparator sortBlock = ^(id string1, id string2)
    {
        return [string1 compare:string2];
    };
    
    //利用数组的sortedArrayUsingComparator调用 NSComparator ，obj1和obj2指的数组中的对象
    NSArray *sortArray = [stringArray sortedArrayUsingComparator:sortBlock];
    NSLog(@"sortArray = %@", sortArray);
    
    
    
    //或者(升序)
    NSArray *sortArray1 = [stringArray sortedArrayUsingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
        return [obj1 compare:obj2];
    }];
    NSLog(@"sortArray1 = %@", sortArray1);

降序

    NSArray *numArray = [NSArray arrayWithObjects:@1,@21,@12,@13,@05, nil];
    NSArray *sortNumArray = [numArray sortedArrayUsingComparator: ^(id obj1, id obj2) {
        if ([obj1 integerValue] > [obj2 integerValue]) {
            return (NSComparisonResult)NSOrderedAscending;
        }
        if ([obj1 integerValue] < [obj2 integerValue]) {
            return (NSComparisonResult)NSOrderedDescending;
        }
        return (NSComparisonResult)NSOrderedSame;
    }];
    NSLog(@"sortNumArray = %@",sortNumArray);