Swift Xcode 6.1 broke my code | Operand error

Question

So whenever I have this:

let result = SKScrollingNode(color: UIColor.clearColor(), size:CGSizeMake(CGFloat(containerWidth), image.size.height));

I get a compilation error for the image.size.height, telling me that "'UIImage?' does not have a member named 'size' although it does

Any idea what this means and how to fix it?

Thanks!

Entire code fragment:

class func scrollingNode(imageNamed: String, containerWidth: CGFloat) -> SKScrollingNode {
    let image = UIImage(named: imageNamed);

    let result = SKScrollingNode(color: UIColor.clearColor(), size: CGSizeMake(CGFloat(containerWidth), image.size.height));
    result.scrollingSpeed = 1.0;

    var total:CGFloat = 0.0;
    while(total < CGFloat(containerWidth) + image.size.width!) {
        let child = SKSpriteNode(imageNamed: imageNamed);
        child.anchorPoint = CGPointZero;
        child.position = CGPointMake(total, 0);
        result.addChild(child);
        total+=child.size.width;
    }
    return result;

Still doesn't work: UIImage.size.height. Getting the same error, so that's not the problem — Sarah, Nov 03 '14 at 15:39
Take a look at this answer: http://stackoverflow.com/questions/26582035/in-xcode-6-1-uiimage-does-not-have-a-member-named-size-error — Rodrigo Borges, Nov 03 '14 at 15:44
Can you please explain this bit: "Use optional chaining to unwrap the optional of image and use frame property of the UIImage." Don't quite get it. — Sarah, Nov 03 '14 at 15:48
Can you please show it in my code? You can edit it if you want — Sarah, Nov 03 '14 at 15:48

score 4 · Accepted Answer · answered Nov 03 '14 at 16:06

In this line:

let image = UIImage(named: imageNamed)

image is an optional, UIImage?.

The error on this line:

let result = SKScrollingNode(color: UIColor.clearColor(), size: CGSizeMake(CGFloat(containerWidth), image.size.height));

can be narrowed down to this piece of code:

CGSizeMake(CGFloat(containerWidth), image.size.height)

CGSizeMake requires 2 CGFloat parameters, but the 2nd one is an optional, because image is an optional:

if image is not nil, image.size.height evaluates to a CGFloat
if image is nil, image.size.height evaluates to nil

In order to avoid that, you have 2 options:

make image a non optional by using forced unwrapping
```
let image = UIImage(named: imageNamed)!
```
but I do not recommend using it because if the UIImage creation fails, the app will crash.

Use optional binding:

let image = UIImage(named: imageNamed);
if let image = image {    
    let result = SKScrollingNode(color: UIColor.clearColor(), size: CGSizeMake(CGFloat(containerWidth), image.size.height));
    // ... rest of the code here
}

this is a better way to unwrap the optional, because in case it's nil, the code in the if statement will be skipped and no runtime error will occur.

Swift Xcode 6.1 broke my code | Operand error

1 Answers1