Understanding `addSubview` and `removeFromSuperview` in Swift

In iOS app development, the ability to manipulate views dynamically is crucial for creating rich, interactive user interfaces. Swift provides methods like `addSubview` and `removeFromSuperview` to modify views during runtime. This article delves into these methods, explaining their usage, nuances, and technical implications.

Core Concepts

UIView

`UIView` is a fundamental building block in iOS. All visible user interface elements in iOS apps are either `UIView` objects or objects that inherit from `UIView`. Each view object defines a rectangular region on the screen and manages the content in that area.

Hierarchy of Views

iOS apps utilize a hierarchical view structure where views can contain other views (subviews). This hierarchy helps organize the user interface elements conveniently.

`addSubview`

The method `addSubview(_:)` is used to add a view as a subview to another view. This method is a part of the `UIView` class and is essential for view hierarchy manipulation.

Syntax:

• Parameters:
  • `view`: The view to be added as a subview.
• The method establishes a parent-child relationship between views.
• The subview retains its own frame and bounds, independent of its parent.
• By default, subviews are rendered above their parent view's content unless explicitly modified by view-z ordering.
• No Parameters: This method does not take any parameters.
• When a view is removed, it no longer participates in the display or event handling.
• Removing a view does not destroy it; it can be reintegrated elsewhere in a view hierarchy.
• Removing a view also disconnects all its subviews, detaching the entire subtree.
• Adding New Elements: Utilize `addSubview` when you need to introduce new visual components dynamically, such as pop-up notifications or appended data entries.
• Modular Design: Design modular screens where components can be rearranged, added, or removed based on user interactions or data changes using these methods.
• Retain Cycles: Removing a view doesn’t break any potential retain cycles. Ensure that no strong references keep the removed view in memory.
• Performance: Excessive or frequent manipulation of the view hierarchy can impact performance. Batch changes where possible, such as during a single `UIView.animateWithDuration` block.