对 NSMutableDictionary 进行排序 [英] Sort an NSMutableDictionary

问题描述

我有一个 NSMutableDictionary 将 NSString 映射到 NSString(虽然值是 NSStrings，但它们确实是只是整数).

I have an NSMutableDictionary that maps NSString to NSString (although the values are NSStrings, they are really just integers).

例如考虑以下映射，

"dog" --> "4"
"cat" --> "3"
"turtle" --> "6"

我希望以值的降序排列字典中的前 10 个条目.有人可以给我看代码吗?也许有一个键数组和另一个值数组.不管怎样，我不介意.我只是想让它更有效率.

I'd like to end up with the top 10 entries in the dictionary sorted by decreasing order of the value. Can someone show me code for this? Perhaps there is an array of keys and another array of values. However it is, I don't mind. I'm just trying to have it be efficient.

谢谢！

推荐答案

获取值的数组，对该数组进行排序，然后获取该值对应的键.

Get the Array of the Values, sort that array and then get the key corresponding to the value.

您可以通过以下方式获取值:

You can get the values with:

NSArray* values = [myDict allValues];
NSArray* sortedValues = [values sortedArrayUsingSelector:@selector(comparator)];

但是，如果集合如您在示例中所示，(我的意思是，您可以从键推断值)，您始终可以对键进行排序，而不是与值混淆.

But, if the collection is as you show in your example, (I mean, you can infer the value from the key), you can always sort the keys instead messing with the values.

使用:

NSArray* sortedKeys = [myDict keysSortedByValueUsingSelector:@selector(comparator)];

比较器是一个消息选择器，它被发送到您要订购的对象.

The comparator is a message selector which is sent to the object you want to order.

如果你想对字符串进行排序，那么你应该使用 NSString 比较器.NSString 比较器是:caseInsensitiveCompare 或 localizedCaseInsensitiveCompare:.

If you want to order strings, then you should use a NSString comparator. The NSString comparators are i.e.: caseInsensitiveCompare or localizedCaseInsensitiveCompare:.

如果这些都不适合你，你可以调用自己的比较器函数

If none of these are valid for you, you can call your own comparator function

[values sortedArrayUsingFunction:comparatorFunction context:nil]

成为比较器函数(来自 Apple 文档)

Being comparatorFunction (from AppleDocumentation)

NSInteger intSort(id num1, id num2, void *context)
{
    int v1 = [num1 intValue];
    int v2 = [num2 intValue];
    if (v1 < v2)
        return NSOrderedAscending;
    else if (v1 > v2)
        return NSOrderedDescending;
    else
        return NSOrderedSame;
}

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