具有自定义视图的Xcode自动布局

Question

I am working on my first project using Auto Layout and custom views. My question is this:

I created my custom view in Interface Builder then added constraints to stretch the view if needed which is working the way I want it to, however, consider the following code snippet from my custom view class -

// MyCustomView

-(id)initWithCoder:(NSCoder*)decoder
{
    self = [super initWithCoder:decoder];
    if(self != nil)
    {
        CGFloat layerWidth = self.bounds.size.width;
                CGFloat layerHeight = self.bounds.size.height;
    }
    return self;
}

This code return the size set in IB. My drawing code relies on the new width and height (if the view has been stretched) but I don't know how to retrieve them.

Answer 1

First, that code is utterly silly because you are creating variables layerWidth and layerHeight and throwing them away, which is pointless.

Second, self.bounds.size is always the view's width and height. However, it is pointless to ask about this in initWithCoder: , which (as you have rightly seen) happens long before the view is put into the interface and even longer before the auto layout takes place that resizes it. If your drawing code relies on the bounds size, then retrieve the bounds size when you draw . If you need to draw again because the view has changed size, and if this is not happening all by itself, then implement layoutSubviews to tell the view that it needs to be drawn again.