coredata如何将默认NSSet更改为NSMutableArray [英] coredata how to change default NSSet to NSMutableArray

问题描述

CoreData一对多默认生成 NSSet ，如何更改 NSSet 为 NSMutableArray ？我尝试手动更改，但得到错误：

CoreData one-to-many default to generate NSSet ,how to change NSSet to NSMutableArray?I try to change it manually,but get error:

 _NSFaultingMutableSet filteredArrayUsingPredicate:]: unrecognized selector sent to instance 0x1ed35e40'

推荐答案

NSSet 具有 allObjects 的方法，它返回 NSArray 。

NSSet has the method allObjects, which returns an NSArray.

要获得 NSMutableArray ，您可以这样做：

To get an NSMutableArray you could do this:

NSMutableArray *array = [NSMutableArray arrayWithArray:myCoreDataObject.mySet.allObjects];

注意：订单不能保证每次都一样如果命令对您很重要，请考虑使用 NSOrderedSet 。

Note: order is not guaranteed to be the same every time (sets aren't ordered). If order is important to you, consider an NSOrderedSet instead.

另请参阅 NSSet ：

https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSSet_Class/Reference/Reference.html

PS：

出现错误的原因：

NSSet （或 _NSFaultingMutableSet ）没有一个方法 filteredArrayUsingPredicate 。

NSSet (or _NSFaultingMutableSet for that matter) doesn't have a method called filteredArrayUsingPredicate.

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