How to create a UIImageView in swift programatically in a separate function?

Question

I want to programatically create an image view in a function. This will hold the background of the image view and some logos - then in all my other image views I can just all the function and I wan't have to do the same thing on each one.

I created a blank swift file and put the following in it:

import Foundation
import UIKit

func background() {

    var imageView : UIImageView
    imageView  = UIImageView(frame:CGRectMake(10, 50, 100, 300));
    imageView.image = UIImage(named:"image.jpg")
    self.view.addSubview(imageView)

}

The only error I got was on the self.view.addSubview(imageView) line. The error message was Use of unresolved identifier 'self'. I tried just removing the word self so the line said this instead view.addSubview(imageView) but then Use of unresolved identifier 'view'.

My question is what am I doing wrong?

Thanks

EDIT:

So I have changed it to this now, is this correct?

import Foundation import UIKit

class MyViewController: UIViewController {

    func background() {

        var imageView : UIImageView
        imageView  = UIImageView(frame:CGRectMake(10, 50, 100, 300));
        imageView.image = UIImage(named:"bg.png")
        self.view.addSubview(imageView)

    }

}

I no longer get any errors in that part but when calling the function from the viewcontroller class I get the error message Use of unresolved identifier 'background'. I should add that I am calling it in the other document by doing thisbackground()` in the view did load function.

I've tried calling it doing background() which gave me the error message Use of unresolved identifier 'background' and I also tried calling it using MyViewController.background() and got the error message Missing parameter for #1 in call. — cross
– cross, Commented Apr 1, 2015 at 15:04
background() is an instance method which means it can all be called on an instance of your class. MyViewController.background() thinks it's a class method. — aahrens
– aahrens, Commented Apr 1, 2015 at 15:06
@aahrens So to make sure I get this right, I am calling it wrong? I should be calling it as an instance of the class - the way I am calling it thinks it is a class method? Would it be better if it was a class method? I'm a bit confused because both of those ways didn't work. — cross
– cross, Commented Apr 1, 2015 at 15:10

Community · Accepted Answer · 2017-05-23 10:26:43Z

To call an instance function in swift you can do it two ways, one from within another instance function or by creating a instance of the class and then calling it.

From an instance function:

class MyViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Called from within another instance function
        self.background()
    }

    func background() {

        var imageView : UIImageView
        imageView  = UIImageView(frame:CGRectMake(10, 50, 100, 300));
        imageView.image = UIImage(named:"bg.png")
        self.view.addSubview(imageView)

    }

}

Or somewhere else in code you can create an instance and call background like this:

func someOtherFunction() {
// Create instance and then call background
        var myView:MyViewController = MyViewController()
        myView.background()
    }

I would recommend you learn the difference between a instance method vs a class method and decide what you are trying to do: What is the difference between class and instance methods?

aahrens · Accepted Answer · 2015-04-01 14:52:57Z

0

You need a class that is a subclass of UIViewController in order to have access to the view property

answered Apr 1, 2015 at 14:52

aahrens

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2 Comments

cross Over a year ago

Thanks for your answer. I have updates my question with the issue this is not giving me.

aahrens Over a year ago

I would change your class name to be more descriptive. Like class MyViewController : UIViewController

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