无法设置translatesAutoresizingMaskIntoConstraints

Question

In an attempt to solve an Auto-Layout issue related to programmatically adding sub views to a scroll view, I have run into many references throughout the internet that, in various scenarios say to set translatesAutoresizingMaskIntoConstraints = YES or translatesAutoresizingMaskIntoConstraints = NO , depending on the case.

However, in Swift, when I type:

var view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false

I get the in-line error: Cannot assign to 'translatesAutoresizingMaskIntoConstraints' in 'view' . Why? Because, when inspected, you'll find that it's a parameterless function, not a property.

I've gotten around this by subclassing, but it's a major inconvenience to have to subclass every view I'm dealing with, just to set translatesAutoresizingMaskIntoConstraints :

class CardView: UIView {
    override func translatesAutoresizingMaskIntoConstraints() -> Bool {
        return false
    }
}

Does anyone know a way around this, or can shed light on the discrepancy between what the general internet councils tell you and what you can actually do, in Swift?

Answer 1

translatesAutoresizingMaskIntoConstraints is actually a method on UIView and not a property.

The syntax works because ObjC lets you use dot-notation for calling methods as well (there's a whole other discussion on how properties actually auto-generate getter/setter methods).

Use the method instead of trying to use the property notation from ObjC

view.setTranslatesAutoresizingMaskIntoConstraints(false) 

Answer 2

请改用view.setTranslatesAutoresizingMaskIntoConstraints(false) 。

Answer 3

迅捷2

view.translatesAutoresizingMaskIntoConstraints = false

Answer 4

If you create any views in code like text views, buttons, labels, etc. You need to be careful how you add Auto Layout constraints to them. The reason for this is that iOS creates constraints for you that match the new view's size and position, and if you try to add your own constraints these will conflict and your app will break.

Lets take an example for a uilabel:

let titleLabel = UILabel()
titleLabel.translatesAutoresizingMaskIntoConstraints = false

Likewise in your case:

let newView = UIView(frame: CGRectZero)
addSubview(newView)
newView.translatesAutoresizingMaskIntoConstraints = false