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iOS Build a Simple iPhone App with Swift 2.0 Improving Our User Interface Changing the Background Color

Posted by John Cotton
John Cotton
10,936 Points

Challenge Task 2 of 2 Now that we have an instance of UIColor as a stored property, let's change the background color

Challenge Task 2 of 2

Now that we have an instance of UIColor as a stored property, let's change the background color of the backing view.

Access the view controller's backing view and assign the UIColor instance to the view's backgroundColor property. Oops! It looks like Task 1 is no longer passing.

When I assign backgroundColor the value of blueColor it invalidates task 1.

colors.swift 
class ViewController: UIViewController {
   let blueColor = UIColor (red:0, green: 0, blue: 255, alpha: 1.0)
   let backgroundColor = UIColor.blueColor
    override func viewDidLoad() {
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        // Dispose of any resources that can be recreated
    }
}

1 Answer

Florin Veja
Florin Veja
6,912 Points

John,

remember that UIColor takes a CGFloat, basically a floating point number, between 0 and 1, not an Int between 0 and 255. When you create your blue color, you will need to divide your red, green, blue numbers by 255.

For the first part of the Challenge:

let blueColor = UIColor(red:0/255.0, green: 0/255.0, blue: 255/255.0, alpha: 1.0)

or you could do

let blueColor = UIColor(red:0.0, green: 0.0, blue: 1.0, alpha: 1.0)

or, yet another way, my favorite

let blueColor = UIColor.blueColor()

For the second part of the Challenge:

Each view has an instance variable named "view" that you can access in your code. You will need to add this to your viewDidLoad function:

    override func viewDidLoad() {
        // Do any additional setup after loading the view, typically from a nib.
        view.backgroundColor = blueColor
    }

Florin