Swift: Array not mutating between classes?

Question

I'm working on a swift project where I create a custom keyboard. In my ViewController, I store and mutate an array of UIImages. Then, in my Keyboard module in my keyboardViewcontroller.swift I would like to use the data I have in this array to create buttons. However, when I try to access the array in KeyBoardViewController it seems to give me an empty array and throws an index out of bounds error. What is strange to me is that in ViewController I print out the size of my array and it is definitely not empty. Here is how I'm storing the array:

import UIKit
class Main {
    var pics :[UIImage]
    init(pics : [UIImage]) {
        self.pics = [UIImage]()
    }
}
var instance = Main(pics: [UIImage]())

In ViewController I mutate it with instance.pics.append...

In my KeyboardViewController:

for image in instance.pics {
...
}

Why would this show as an empty array in KeyboardViewController? Thanks

Exactly. Instead of asigning the passed pics argument to self.pics, you are assigning a new, empty array ([UIImage]()). — Nicolas Miari
– Nicolas Miari, Commented Dec 28, 2015 at 1:59
Incidentally, the argument passed to the initializer also is an empty array of UIImage. What would you expect to happen? — Nicolas Miari
– Nicolas Miari, Commented Dec 28, 2015 at 2:00

timbo · Accepted Answer · 2015-12-28 02:02:11Z

1

Rather than assigning an empty array of UIImage objects, the following will set the internal array variable to be a copy of the myPics array.

import UIKit

class Main {
    var pics: [UIImage]
    init(pics: [UIImage]) {
        self.pics = pics
    }
}

var instance = Main(pics: myPics)

answered Dec 28, 2015 at 2:02

timbo

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2 Comments

Alex Over a year ago

Thank you! this looks like what I was looking for. one more question though, what is myPics? Is this an array I should create elsewhere? If I try to create an array in ViewController called myPics and say Main(pics: myPics) it says myPics not found

timbo Over a year ago

If you have an existing array of UIImages that you want to save in the Main class, then that would be myPics. Otherwise, create a Main init that simply initialises pics as an empty array.

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