Swift Property Observers: How willSet and didSet Automate Change Reactions

Swift structs support property observers — willSet and didSet — that automatically execute code before or after a property's value changes. Without observers, developers must manually call functions after every property update, making it easy to introduce silent bugs when a call is forgotten. The didSet observer runs after a change and provides oldValue, while willSet fires before the change and supplies newValue, both without requiring explicit declarations. In practice, didSet is more commonly used for tasks like updating UI, logging, or saving data, whereas willSet is useful when the pre-change state needs to be captured. SwiftUI itself leverages willSet internally to snapshot the interface before animations, illustrating the observer pattern's role beyond basic debugging.