使用NSPredicate(可可)比较2个数组 [英] comparying 2 array's with NSPredicate (cocoa)

问题描述

我有一个NSObject带有2个属性的

i have an NSObject with 2 property's

@interface Entity : NSObject  {

     NSNumber *nid;
     NSString *title;
}

我有2个数组，其中包含Entity的对象，我想在nid上将这两个数组与谓词进行比较

i have 2 array's with Entity's objects in it and I want to compare those two on the nid with a predicate

array1: ({nid=1,title="test"},{nid=2,title="test2"})
array2: ({nid=2,title="test2"},{nid=3,title="test3"})

这2个数组的nid都为2，所以我的输出应该是

the 2 arrays have both a nid with value 2 so my output should but

array3: ({nid=2,title="test2"})

所以我可以产生一个只有匹配的nid的数组

so i can produce an array with only matching nid's

推荐答案

以下代码似乎对我有用(它显然泄漏了MyEntity对象，但这不是示例目标):

The following code seems to work for me (it obviously leaks MyEntity objects but that was not the sample target):

NSArray* array1 = [NSArray arrayWithObjects:[[MyEntity alloc] initWithID:[NSNumber numberWithInt:1] title:@"1"], 
                   [[MyEntity alloc] initWithID:[NSNumber numberWithInt:2] title:@"2"], nil];

NSArray* array2 = [NSArray arrayWithObjects:[[MyEntity alloc] initWithID:[NSNumber numberWithInt:2] title:@"2"], 
                   [[MyEntity alloc] initWithID:[NSNumber numberWithInt:3] title:@"3"], nil];

NSArray* idsArray = [array1 valueForKey:@"nid"];
NSArray* filteredArray = [array2 filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"nid IN %@", idsArray]];

filteredArray 包含两个数组中都存在ID的实体.

filteredArray contains entities whose ids present in both array.

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