有没有办法遍历字典?

问题描述

我知道 NSDictionaries 需要一个 key 才能获得 value.但是如何遍历 NSDictionary 中的所有 keys 和 values，以便我知道有哪些键以及有哪些值?我知道在 JavaScript 中有一种叫做 for-in-loop 的东西.Objective-C 中是否有类似的东西?

I know NSDictionaries as something where you need a key in order to get a value. But how can I iterate over all keys and values in a NSDictionary, so that I know what keys there are, and what values there are? I know there is something called a for-in-loop in JavaScript. Is there something similar in Objective-C?

推荐答案

是的，NSDictionary 支持快速枚举.使用 Objective-C 2.0，您可以这样做:

Yes, NSDictionary supports fast enumeration. With Objective-C 2.0, you can do this:

// To print out all key-value pairs in the NSDictionary myDict
for(id key in myDict)
    NSLog(@"key=%@ value=%@", key, [myDict objectForKey:key]);

替代方法(如果您的目标是 Mac OS X 10.5 之前的版本，则必须使用该方法，但您仍然可以在 10.5 和 iPhone 上使用)是使用 NSEnumerator:

The alternate method (which you have to use if you're targeting Mac OS X pre-10.5, but you can still use on 10.5 and iPhone) is to use an NSEnumerator:

NSEnumerator *enumerator = [myDict keyEnumerator];
id key;
// extra parens to suppress warning about using = instead of ==
while((key = [enumerator nextObject]))
    NSLog(@"key=%@ value=%@", key, [myDict objectForKey:key]);

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