获取按其相应值排序的NSDictionary键 [英] Getting NSDictionary keys sorted by their respective values

问题描述

我有一个 NSMutableDictionary 与整数值，我想得到一个数组的键，按升序排序他们各自的值。例如，使用此字典：

I have an NSMutableDictionary with integer values, and I'd like to get an array of the keys, sorted ascending by their respective values. For example, with this dictionary:

mutableDict = {
    "A" = 2,
    "B" = 4,
    "C" = 3,
    "D" = 1,
}

$ b b

我想结束数组 [D，A，C，B] 。

推荐答案

NSDictionary 方法 keysSortedByValueUsingComparator：应该做的伎俩。

The NSDictionary Method keysSortedByValueUsingComparator: should do the trick.

您只需要一个返回 NSComparisonResult 的方法，比较对象的值。

You just need a method returning an NSComparisonResult that compares the object's values.

您的字典是

NSMutableDictionary * myDict;

您的数组

NSArray *myArray;

myArray = [myDict keysSortedByValueUsingComparator: ^(id obj1, id obj2) {

     if ([obj1 integerValue] > [obj2 integerValue]) {

          return (NSComparisonResult)NSOrderedDescending;
     }
     if ([obj1 integerValue] < [obj2 integerValue]) {

          return (NSComparisonResult)NSOrderedAscending;
     }

     return (NSComparisonResult)NSOrderedSame;
}];

只需使用 NSNumber 。

BTW，这取自：
https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Collections/Articles/Dictionaries.html

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