使用 NSPredicate 的不同对象

发布于 2024-12-24 16:55:31 字数 312 浏览 0 评论 0原文

我有一个自定义对象的 NSArray。考虑自定义对象具有 PageNumber 属性。我想用“customObject.PageNumber is unique”之类的条件过滤我的 NSArray。

我知道我可以循环遍历数组并消除具有重复页码的对象。但有没有什么简单的方法可以做到呢？我已经尝试过，

[myarray valueForKeyPath:@"distinctUnionOfObjects.pageNumber"];

它给了我唯一的页码（如 7、8、9）。但我想要自定义对象本身而不仅仅是页码。任何谓词可以帮助我吗？

原文

I have an NSArray of custom objects. Consider that the custom objects have a PageNumber property. I would like to filter my NSArray with a condition like "customObject.PageNumber is distinct".

I know I can loop through the array and eliminate object with duplicate pageNumbers. But is there any easy way to do it? I have tried,

[myarray valueForKeyPath:@"distinctUnionOfObjects.pageNumber"];

It is giving me the unique page numbers (like 7, 8, 9). But I want the custom object itself rather than just page numbers. Can any predicate help me?

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甜味超标? 2024-12-31 16:55:31

我创建了一个简单的库，称为 Linq to ObjectiveC，它是使此类问题更容易解决的方法的集合。在您的情况下，您需要 Linq-to-ObjectiveC different 方法：

NSArray* itemsWithUniquePageNumbers = [items distinct:^id(id item) {
    return [item pageNumber];
}];

这会返回一个对象数组，每一页都有唯一的页码。

I have created a simple library, called Linq to ObjectiveC, which is a collection of methods that makes this kind of problem much easier to solve. In your case you need the Linq-to-ObjectiveC distinct method:

NSArray* itemsWithUniquePageNumbers = [items distinct:^id(id item) {
    return [item pageNumber];
}];

This returns an array of objects, each one with a unique page number.

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薔薇婲 2024-12-31 16:55:31

是的，这可以在 NSPredicate 的帮助下实现。

customObject=[(NSArray*)[myArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"self.PageNumber==%d",pageNumber]] lastObject];
//pageNumber is an integer

过滤后的数组是自定义对象的 NSArray，它是使用谓词进行过滤的结果。由于您的页码是唯一的，因此它将仅返回一个对象的数组。我们通过向其传递 lastObject 消息来获取该信息。

参考：
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/predicates.html#//apple_ref/doc/uid/TP40001798-SW1

Yes, that is possible with the help of NSPredicate

customObject=[(NSArray*)[myArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"self.PageNumber==%d",pageNumber]] lastObject];
//pageNumber is an integer

The filtered array is an NSArray of your custom objects which is the result of filtering using the predicate. Since your page number is unique, it will return only an array of one object. We get that by passing lastObject message to it.

Refer:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/predicates.html#//apple_ref/doc/uid/TP40001798-SW1

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