layoutSubviews

layoutSubviews is a method in the UIKit framework for iOS development. It is called on a UIView whenever the view's bounds change, which typically occurs when the view is first displayed or when its size or position is adjusted. The primary purpose of layoutSubviews is to determine and set the positions and sizes of the view's subviews.

When layoutSubviews is invoked, it is the responsibility of the developer to implement the logic that arranges the subviews within the receiver's bounds. This often involves calculating new frames for each subview based on the receiver's updated dimensions. For example, a custom view might override layoutSubviews to center its subviews, distribute them evenly, or arrange them in a specific grid.

It is important to call the superclass's implementation of layoutSubviews within an overridden method. This ensures that any default layout behavior provided by the superclass, such as adjusting constraints or handling automatic layout, is preserved. Failing to call super can lead to unexpected visual glitches or incorrect layout behavior.

Developers should avoid directly calling layoutSubviews. Instead, they should rely on system-initiated calls or explicitly request a layout update by calling setNeedsLayout(). The setNeedsLayout() method marks the view as needing a layout update, and the system will call layoutSubviews at an appropriate time, usually before the next screen draw. This deferred execution helps optimize the layout process by performing multiple layout-related updates efficiently.