View Life Cycle SwiftUI

.

1. onAppear

• Purpose: Called every time the view appears.
• UIKit Equivalent: Similar to viewWillAppear.
• Use Case: Trigger events or API calls each time a view appears.
• not triggered by state changes.
• Example:

.onAppear {
    print("View appeared")
    fetchData()
}

• Behavior: Automatically triggers every time the view re-enters the screen.

2. onDisappear

• Purpose: Called every time the view disappears.
• UIKit Equivalent: Similar to viewWillDisappear.
• Use Case: Cleanup tasks or saving states when the view disappears.
• Example:

.onDisappear {
    print("View disappeared")
}

Extending onAppear to Mimic viewDidLoad

• SwiftUI lacks a direct equivalent of viewDidLoad (one-time event).
• Solution:
• Use a @State Boolean variable to differentiate between the first load and subsequent appearances.
• Example:

@State private var isFirstLoad = false

.onAppear {
    if !isFirstLoad {
        print("View loaded for the first time")
        isFirstLoad = true
        fetchData()
    } else {
        print("View appeared again")
    }
}