比较Obj-C中的对象 [英] Comparing objects in Obj-C

问题描述

如何比较Objective-C中的对象?

How does one compare objects in Objective-C?

像==一样简单吗?

我要检查对象数组，如果不存在，则将其添加到数组中，否则将其从数组中删除.

I want to check an array for an object and if it doesnt exist add it to the array otherwise, remove it from the array.

推荐答案

在Objective-C中比较对象的工作方式与Java或其他面向对象的语言几乎相同:

Comparing objects in Objective-C works much the same as in Java or other object-oriented languages:

• ==比较对象引用；在Objective-C中，它们是否占用相同的内存地址.
• isEqual:，在 NSObject ，检查两个对象是否相同".您可以重写此方法来为对象提供自己的相等性检查.

• == compares the object reference; in Objective-C, whether they occupy the same memory address.
• isEqual:, a method defined on NSObject, checks whether two objects are "the same." You can override this method to provide your own equality checking for your objects.

因此通常要做的是，你会做的:

So generally to do what you want, you would do:

if(![myArray containsObject:anObject]) {
    [myArray addObject:anObject];
}

之所以可行，是因为 NSArray 有一个称为containsObject:的方法，该方法将isEqual:消息发送到它包含的每个对象，并以您的对象作为参数.除非isEqual:的实现依赖于==，否则它不使用==.

This works because the Objective-C array type, NSArray, has a method called containsObject: which sends the isEqual: message to every object it contains with your object as the argument. It does not use == unless the implementation of isEqual: relies on ==.

如果要完全使用实现的对象，请记住可以覆盖isEqual:来提供自己的相等性检查.通常，这是通过比较对象的字段来完成的.

If you're working entirely with objects that you implement, remember you can override isEqual: to provide your own equality checking. Usually this is done by comparing fields of your objects.

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