快速方法来总结NSSet中的所有对象的属性？ [英] Quick way to sum a property of all objects within an NSSet?

问题描述

我想有一种方法可以快速请求 NSSet 来轮询其成员，并返回一个 NSInteger 属性在每个对象，但我可能会很困惑这与Mac OS X的东西。这是否存在于Cococa Touch？

I thought there was a way to quickly ask a NSSet to poll its members and return a sum of say an NSInteger property in each of its objects, but I may very well be confusing this with the Mac OS X side of things. Does this exist in Cococa Touch?

我能找到的最接近的是 objectEnumerator ，我想我可以步枪通过每个对象和增量我自己的变量。

The closest thing I can find is objectEnumerator, whereby I suppose I could rifle through each object and increment my own variable. Does the better way exist?

推荐答案

如果你想找到给定属性的总和（ theSet ）的每个成员的每个成员都可以执行以下操作：< /> theIntegerPropertyToSum p>

If you're trying to find the sum of a given property (theIntegerPropertyToSum) for each member of an array/set-derived class that's KVC-compliant (theSet), you can do the following:

NSNumber* theSum = [theSet valueForKeyPath:@"@sum.theIntegerPropertyToSum"];

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