如何使子对象搜索更简洁？

Question

I am interested in a terse way to do a lookup for a match within an array that requires levels of sub-objects. The performance does not have to be close to ideal but should be reasonable.

For this case I do not want to add a reverse relationship or manage retained dictionaries . I don't want to change the model at all.

Object1 contains an Object2, and Object2 contains an Object3. I understand that the following method will return the first match, however a solution that returns every match would also be acceptable.

-(Object1*)getObject1ForObject3:(Object3*)object3
{
    for(Object1 *object1 in self.object1s)
        if(object1.object2.object3 == object3)
            return  object1 ;

    return nil ;
}

And for prestige, can we make it terse if there is a to-many relationship in the middle?

-(Object1*)getObject1ForObject3:(Object3*)object3
{
    for(Object1 *object1 in self.object1s)
        for(Object2 *object2 in object1.object2s)
            if(object2.object3 == object3)
                return  object1 ;

    return nil ;
}

Answer 1

Well, the API for declaring an NSPredicate isn't exactly terse , but it's still probably more terse than what you're doing.

For the first case, where there's not a to-many in the middle:

NSPredicate *pred = [NSPredicate predicateWithFormat:@"object2.object3 == %@", object3];
NSArray *matchingObj1s = [self.object1s filteredArrayUsingPredicate];

When there's a to-many relationship in the middle:

NSPredicate *pred = [NSPredicate predicateWithFormat:@"ANY object2s.object3 == %@", object3];
NSArray *matchingObj1s = [self.object1s filteredArrayUsingPredicate];