A framework which helps you attach observers to `UIView`s to get updates on its frame changes

FrameObserver is a framework that lets you attach observers to any UIView subclass and get notified when its size changes. It doesn't use any Method Swizzling or KVO so it'll be perfectly safe to use. It is especially useful when dealing with entities that require you to supply a CGRect to them, e.g CAGradientLayer.

Installation

CocoaPods

CocoaPods is a dependency manager for Cocoa projects. You can install it with the following command:

$ gem install cocoapods

Then, to add FrameObserver to your project, specify FrameObserver in your Podfile:

source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '9.0'
use_frameworks!

target '' do
    pod 'FrameObserver'
end

Usage

• Using closures:

view.addFrameObserver { frame, bounds in // get updates when the size of view changes
    print("frame", frame, "bounds", bounds)
}

• Using the delegate pattern:

class SomeViewController: UIViewController, FrameChangeDelegate {

    func frameChangeDelegateDidChange(for view: UIView, _ frame: CGRect, _ bounds: CGRect) {
        if view == self.view {
            print("frame", frame, "bounds", bounds)
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addFrameObserver(with: self)
    }

}

You can call these on any UIView subclass, such as UIButton, UIStackView, etc.

The underlying implementation of this framework adds a totally invisibile, untappable view as a subview of the view you want to get notified about its frame. Thus, if you attach an observer to a UIView subclass, and for whatever reason remove all of its subviews, make sure you add the observer again.

override func viewDidLoad() {
    super.viewDidLoad()
    view.addFrameObserver(with: self)

    for subview in view.subviews {
        subview.removeFromSuperview()
    }

    // the observer no longer exists, recreating it again
    view.addFrameObserver(with: self)
}

Other functions:

• func removeFrameObserver(): Removes the current observer, if any. There's no need to call this in the deinit of your classes.
• func hasFrameObserver() -> Bool: Returns true if the view has a frame observer.

License

FrameObserver is released under the MIT license. Check the LICENSE file for more details.