如何預取關係的關係NSManagedObject

我正在做一個搜索，需要加快一點。我有一系列汽車零件，我想找到有這些零件的汽車。這部分我很好。 NSManagedObject Cars.h如何預取關係的關係NSManagedObject

（汽車有一個叫NSSet中ToCarParts，其中列出了所有的汽車的汽車零部件）

NSMagagedObject Parts.h （零件有一個叫NSSet中ToCars，其中列出了相關的所有汽車與此）

//This takes all results gathered by using parts to search for car, and converts them to have the main object be a car 
-(NSArray*)convertResultsToCars:(NSArray*)records{ 
    NSMutableArray *manipulator =[NSMutableArray arrayWithArray:records]; 
    NSMutableArray *convertedArray =[[NSMutableArray alloc]init]; 

    for (int i=0; i<[manipulator count]; i++) { 
     CarPart *FromManipulator=(CarPart*)[manipulator objectAtIndex:i]; 
     [convertedArray addObjectsFromArray:[[partFromManipulator toCars]allObjects]]; 
    } 

    NSLog(@"Results from core data = %i",[convertedArray count]); 
    return [NSArray arrayWithArray:convertedArray]; 
}

問題來後，當我從這裏的結果，必須在應用程序後加載的所有carParts。

Car *carResult =(Cars*)[resultsConvertedToCarsArray objectAtIndex:i]; 

     partsFromCar =[NSMutableArray arrayWithArray:[[carResult toParts]allObjects]];

如何在原始查詢中預取上述內容，以便該信息已被加載到對象中？

這是我原來的讀取請求：

NSEntityDescription *entity = [NSEntityDescription entityForName:@"CarParts" inManagedObjectContext:[self managedObjectContext]]; 
[fetchRequest setEntity:entity]; 
    [fetchRequest setPredicate:[self parseCarPartsIntoAPredicate:carPartsArray]]; 
    [fetchRequest setReturnsDistinctResults:YES]; 
    //I guess I would use something like this? but how would I structure it? 
    [fetchRequest setRelationshipKeyPathsForPrefetching:@"I need to prefetch the toParts nsset of the cars found here (although in reality it brings up every instance of that car part, which I then have to convert into a car... something like found a car part, car for that part is a buick, what are the parts of the buick? ok, preload those parts"];

預先感謝您！

來源

2013-01-08 William Falcon

-2

創建一個nsmanagedobject持有這些物品......

來源

2013-01-19 18:03:16

，而不是否決也許一個更好的答案應該給... –

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Post"]; 
[fetchRequest setRelationshipKeyPathsForPrefetching:@[@"Picture"]];

來源

2013-09-15 20:01:39

如何預取關係的關係NSManagedObject

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