How to get only objects of one type from an array?

Question

(Xcode IOS) - I'm trying to make a method which prefetches all the images and loads them into a tableView before scrolling (using SDWebImage). Anyways:

I have an array of messages and each "message" is composed of a few different keys, PFFile, dateCreated, sender, etc...

What I need to do is take this array of @[ [PFFile], [dateCreated], [other info] ] -> @[ [PFFile] ]

In other words, I need to make an array of just the PFFiles from the entire array. I was thinking of something like this (pseudocode)

self.urls = [self.messages objectsWithKey:@[PFFiles]];

Since you're using an array, what do you mean by keys in here? More specifically what are the objects in your array? — TheAmateurProgrammer
– TheAmateurProgrammer, Commented Aug 12, 2014 at 0:54

Acey · Accepted Answer · 2014-08-12 00:53:58Z

1

It sounds like you are asking how to filter an array.

self.urls = [self.messages objectsAtIndexes:[self.messages indexesOfObjectsPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    return [obj isKindOfClass:[PFFile class]];
}]];

I like this syntax because you can use a block to return YES/NO if the object passes any sort of test you might want to write and it's a one-liner.

answered Aug 12, 2014 at 0:53

Acey

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Comments

Tomohiro Takahashi · Accepted Answer · 2014-08-12 00:57:59Z

0

How about using combination of NSDictionary and NSArray ? You can put your array objects in a dictionary object.

answered Aug 12, 2014 at 0:57

Tomohiro Takahashi

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