数组排序与自定义类的实例 [英] Sorting an array with instances of a custom class

问题描述

我充满了包含两个字符串的属性，名字和姓氏的自定义类的实例的数组。两者都有一个getter方法​​，它等于财产本身的名称。也有用于检索一个名为getFullName的人的全名的方法。考虑下面的例子。

I have an array filled with instances of a custom class which contains two String properties, firstname and lastname. Both have a getter method which is equal to the name of the property itself. There is also a method for retrieving the Full name of a person called "getFullName". Consider the example below.

 CustomClass *person = [[CustomClass alloc] ...];
 person.firstname  // Returns "Thomas"
 person.lastname // Returns "Meier"
 [person getFullName] // Returns "Thomas Meier"

现在，我想这个阵列由全名的降序排列。我一直在寻找一些数组排序方法，但不太能弄清楚如何去这件事。我想，我必须创建某种比较函数用于比较两个元素，但我怎么知道哪个值传递给这个方法，我应该在哪里把它（自定义类或类所在的排序发生在SDK ？）。也许有一种要对此另一个/更好的办法？诚然，我已经接近无经验数组排序。

Now I would like to sort this Array by Fullname in a descending Order. I have been looking at some array sorting methods but was not quite able to figure out how to go about this. I guess that I have to create some kind of comparison function which compares two elements, yet how do I tell the SDK which values to pass to this method and where should I place it (in the custom class or in the class where the sorting happens?). Maybe there is another/better way of going about this? Admittedly I have close to none experience with sorting arrays.

非常感谢您的帮助！

诗。在code应该在iOS 3.2中运行

Ps. The code should run on iOS 3.2

推荐答案

有几个方法可以做到这一点。一种是把一个比较法上的自定义类。说它 -compare：或类似的东西。该方法应该采取相同的自定义类型作为其输入的另一目的。它应该返回 NSOrderedAscending ， NSOrderedDescending 或 NSOrderedSame ，视该比较的结果。 （这里面比较功能，你看你自己的全名与传入的对象的全名）。

There are a couple ways to do this. One is to put a comparison method on the custom class. Call it -compare: or something like that. That method should take another object of the same custom type as its input. It should return NSOrderedAscending, NSOrderedDescending, or NSOrderedSame, depending on the result of the comparison. (Inside this compare function is where you look at your own fullName versus the passed-in object's fullName.)

然后你可以使用的NSMutableArray 的<一个href=\"http://developer.apple.com/iphone/library/documentation/cocoa/reference/foundation/Classes/NSMutableArray_Class/Reference/Reference.html#//apple_ref/occ/instm/NSMutableArray/sortUsingSelector%3a\"><$c$c>-sortUsingSelector:方法是这样的：

Then you can use NSMutableArray's -sortUsingSelector: method, like this:

[myArray sortUsingSelector:@selector(compare:)];

这适用于iOS的所有版本。有4.0 +可用块比较的方法。

This works on all versions of iOS. There are block comparison methods available in 4.0+.

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