iOS-NSComparisonResult和NSComparator介绍,比较,排序

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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);

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