coredata如何将默认NSSet更改为NSMutableArray

Question

CoreData一个一对多默认生成NSSet,如何改变NSSet对NSMutableArray我尝试手动改变它,但得到的错误？

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

Answer 1

NSSet有方法allObjects,返回一个NSArray.

为了得到NSMutableArray你可以做到这一点:

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

注意:每次订单不保证相同(订单不订购).如果订单对您很重要,请考虑NSOrderedSet改为.

另见以下文档NSSet:

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

PS:

你说错误的原因是:

NSSet(或者_NSFaultingMutableSet就此而言)没有一种叫做的方法filteredArrayUsingPredicate.