day-065

Day 65: Project 13: Instafilter (Part Four)

Follow along at https://www.hackingwithswift.com/100/swiftui/65.

📒 Field Notes

This day covers Part Four of Project 13: Instafilter in the 100 Days of SwiftUI Challenge. (Project 13 files can be found in the directory for Part One.)

It focuses on several specific topics:

• Building our basic UI
• Importing an image into SwiftUI using UIImagePickerController
• Basic image filtering using Core Image

Basic image filtering using Core Image

This is just one of many cases where tying user interface controls to Combine publishers can really shine.

By tying out slider to a publisher that updates and observed-object value, we can have the slider react to updates continuously... but not too continuously! -- giving it a slight debounce so that we aren't trying to apply image processing with every microscopic drag movement.

View:

Slider(
    value: $viewModel.filterIntensity,
    minimumValueLabel: Text("0"),
    maximumValueLabel: Text("1")
) {
    Text("Intensity")
}

ViewModel ObservableObject:

private var filterIntensityPublisher: AnyPublisher<CGFloat, Never> {
    $filterIntensity
        .debounce(for: .milliseconds(200), scheduler: DispatchQueue.main)
        .eraseToAnyPublisher()
}