Binary operator '==' cannot be applied to operands of type 'Dimension' and 'Float'

[WilliamHua]

I read in #36 and #56 that Cartography should be able to support floats, but I keep on receiving the error Binary operator '==' cannot be applied to operands of type 'Dimension' and 'Float' when I try this code:

        layout(button) { fabButton in
            button.right == button.superview!.right - 16
            button.bottom == button.superview!.bottom - 16
            button.height == Constants.height
            button.width == Constants.width
        }

I have also tried it with CGFloat to no luck

[davidbarsky]

So it seems to me (and I might be wrong! Please correct me) that you don’t have a type error for the first two statements, but your Constants.height and Constants.width are defined as CGFloats. I’ve had something similar happen to me; try dropping the Constants.file, and instead use a raw numerical value. That might solve your type error.

[WilliamHua]

Yes exactly, sorry if it wasn't clear. It works if I just use numerical values.

The only issue is that I can't drop the Constants.file, I the number isn't something I can hardcode.

[davidbarsky]

Are you saying that the values of the Constants file are updated dynamically at runtime, or are these organizational issues at hand?

[WilliamHua]

Yes, the values Constants are updated dynamically at runtime

[davidbarsky]

Alright — I’m largely ignorant of your codebase, but updating a Constants file at runtime seems to be a bit of an anti-pattern. What might get you to the same solution is to pass in height and width values whenever you initialize a view (using a custom initializer), set them to a class’s properties (like buttonHeight, etc.) and use those values to set your button’s height and width. 😃

[WilliamHua]

I understand your concern, it's a bit counter-intuitive. It's dependent on the screen size; that's the only reason it's updated at run-time.

With regards to your solution, wouldn't that still cause an issue since you're using a variable instead of a hardcoded number?

[davidbarsky]

Fair point.

Upon further reflection, have you considered that maybe you might be approaching this problem incorrectly? Auto Layout encourages you to think in relative, constraint-based way, and updating button dimensions at runtime with absolute values goes against that philosophy — that shouldn’t be your job, it’s Auto Layout’s. A constants file make me think that you might be approaching this problem incorrectly.

This apple documentation might prove useful — it explains the philosophy of Autolayout in a really good way. 👍

[WilliamHua]

Thanks for your input (not sarcasm, I appreciate you taking the time to respond to me)! I will look into your suggestions.

However, there are cases (outside of this) where I just need to set the height and width of something based off of dynamic values. If I don't solve this issue, I don't see how I could do that with cartography

[davidbarsky]

I understand that — but those dynamic values should be calculated by Auto Layout.

And again! I don’t understand your codebase, nor the decisions you made. I am totally ignorant. It just seems the problem you’re describing is solved by Auto Layout far more directly.

[robb]

I can't reproduce this on my end, do you have more code that you can share?

[WilliamHua]

I want to create a button of a certain width and height:

layout(button) { button in
        button.right == button.superview!.right - 16
        button.bottom == button.superview!.bottom - 16
        button.height == 56
        button.width == 56
}

However, I would also like to tie the numbers to variables rather than hard coded so I can change all button sizes at once. Ideally it would look like this

layout(button) { button in
        button.right == button.superview!.right - 16
        button.bottom == button.superview!.bottom - 16
        button.height == Constants.height
        button.width == Constants.width
}

In a different file I have this structure

@objc class Constants: NSObject {
    static let height: Float == 56
    static let width: Float = 56
}

With this setup I receive the error Binary operator '==' cannot be applied to operands of type 'Dimension' and 'Float'.

---

For some reason I was under the impression that I attempted this with CGFloat and it failed before, however now when I force the Constants to use CGFloat instead of Float, it works perfectly.

[robb]

👍