遍历NSArray收集特定对象

Question

I can't gather my thoughts at the moments and have problems figuring out a solution to the following:

I have an array of 5 NSObjects , Object-X. Each objects has two objects, Object-Y. Each of these two objects have a 50 objects, Object-Z, inside them.

Something like this.

Object-X 0:
    Object-Y 0:
        Object-Z: 0
        Object-Z: 1
        Object-Z: 2
        ...
    Object-Y 1:
        Object-Z: 0
        Object-Z: 1
        Object-Z: 2
        ...
Object-X 1:
    Object-Y 0:
        Object-Z: 0
        Object-Z: 1
        Object-Z: 2
        ...
    Object-Y 1:
        Object-Z: 0
        Object-Z: 1
        Object-Z: 2
        ...
Object-X 2:
    Object-Y 0:
        Object-Z: 0
        Object-Z: 1
        Object-Z: 2
        ...
    Object-Y 1:
        Object-Z: 0
        Object-Z: 1
        Object-Z: 2
        ...
 ...

Each of the fifty objects (Object-Z) has an CLLocation. I first run through all 500 objects and calculate the distance from the users current location and the objects.

What I would like to then do (preferably at the same time, if possible) is to take the closest Object-Z from each Object-Y in each Object-X and insert it into an array, so I end up with 10 objects.

Answer 1

Instead of calculating distance, and then finding the 10 closest objects, maybe

1. dispatch, say, 5 blocks/threads (using GCD ... or a common multi-threaded approach), which would each
2. calculate 100 distances (for Object-Y[0] and Object-Y[1] of some Object-X[i] ) while
3. keeping track of the objects with the min distance, for both Object-Y[0] and Object-Y[1]

When the blocks/threads finish, they can add the max objects to an array.

Answer 2

距离的存储位置尚不完全清楚，但如果在ObjectZ上，则可以执行[objectXs valueForKeyPath:@"objectYs.objectZs.@min.distance"] 。