What is si-leer?

Si-leer, probably a typo. The correct term related to iOS development might be SwiftUI.

SwiftUI is a declarative UI framework from Apple for creating user interfaces across all Apple platforms (iOS, macOS, watchOS, tvOS). It offers a new approach to building interfaces using Swift, based on describing the desired UI state.

Main concepts of SwiftUI:

• Declarative syntax: You describe how your UI should look for certain data, and the system determines how to update it when data changes.
• State and Data Flow: SwiftUI has built-in mechanisms for managing application state and its changes, leading to automatic UI updates.
• Composition: UI is built from small, reusable View components that can be combined.
• Cross-Platform: The same SwiftUI code can be used to create UI on different Apple platforms, considering platform-specific features.

Example of a simple View in SwiftUI:

// view
import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundColor(.accentColor)
            Text("Hello, SwiftUI!")
        }
        .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

SwiftUI is a modern alternative to UIKit (for iOS) and AppKit (for macOS) and is actively developed by Apple.