xcode 对 NSDictionary 进行降序排序。如何使用 `compare:options:` 选择器发送选项？
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Sorting an NSDictionary, descending. How do I send options with the `compare:options:` selector?
提问by ck_
I am attempting to sort an NSDictionary.
我正在尝试对 NSDictionary 进行排序。
From the Apple docsI see you can use keysSortedByValueUsingSelector:
从Apple docs我看到你可以使用keysSortedByValueUsingSelector：
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:63], @"Mathematics",
[NSNumber numberWithInt:72], @"English",
[NSNumber numberWithInt:55], @"History",
[NSNumber numberWithInt:49], @"Geography",
nil];
NSArray *sortedKeysArray = [dict keysSortedByValueUsingSelector:@selector(compare:)];
which gives:
这使：
// sortedKeysArray contains: Geography, History, Mathematics, English
but I want:
但我想要：
// sortedKeysArray contains: English, Mathematics, History, Geography
I have read that you can use compare:options:, and an NSStringCompareOptionsto change the comparison to compare in the other direction.
我读过您可以使用compare:options:, 和 anNSStringCompareOptions来更改比较以在另一个方向进行比较。
However I don't understand how you send compare:options:with an optionin the selector.
但是我不明白你如何在选择器中发送compare:options:一个选项。
I want to do something like this:
我想做这样的事情：
NSArray *sortedKeysArray = [dict keysSortedByValueUsingSelector:@selector(compare:options:NSOrderDescending)];
How should I switch the order of the comparison?
我应该如何切换比较的顺序？
Related: https://discussions.apple.com/thread/3411089?start=0&tstart=0
相关：https: //discussions.apple.com/thread/3411089?start=0&tstart=0
回答by paulmelnikow
Option 1:Use a comparator to invoke -compare:in reverse: (Thanks Dan Shelly!)
选项 1：使用比较器-compare:反向调用：（感谢 Dan Shelly！）
NSArray *blockSortedKeys = [dict keysSortedByValueUsingComparator: ^(id obj1, id obj2) {
// Switching the order of the operands reverses the sort direction
return [objc2 compare:obj1];
}];
Just reverse the descending and ascending return statements and you should get just what you want.
只需颠倒降序和升序的返回语句，你就会得到你想要的。
Option 2:Reverse the array you have:
选项 2：反转您拥有的数组：
回答by YvesLeBorg
I use :
我用 ：
NSSortDescriptor *sortOrder = [NSSortDescriptor sortDescriptorWithKey:@"self" ascending:NO];
self. sortedKeys = [[self.keyedInventoryItems allKeys] sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortOrder]];
