How can I dynamically add SwiftUI Views to a parent View?

Question

Is it possible to add multiple SwiftUI Views to a parent View dynamically & programmatically?

For example suppose we have a basic View such as:

struct MyRectView: View {
    var body: some View {
        Rectangle()
            .fill(Color.red)
            .frame(width: 200, height: 200)
    }
}

And a Button defined as:

struct MyButtonThatMakesRects: View {

    var body: some View {
        Button(
            action: {
                // Create & add Views to parent here?
                // ...
            },
            label: {
                Text("tap to create a Rect")
            }
        )
    }
}

Is there any way I can create multiple instances of MyRectView in a parent View when MyButtonThatMakesRects is tapped?

My initial thinking was in line with how I would do this in UIKit. That being on button tap, create a new UIView(), and then use .addSubview(...) to add it to a parent. Not sure if SwiftUI has similar functionality. Or maybe there is a simpler way to do this that I'm not seeing?

Brock Batsell · Accepted Answer · 2020-04-08 23:14:44Z

13

SwiftUI is functional and reactive, so its output is entirely a reflection of state. You'll have to store and manipulate state that results in a SwiftUI view with your desired outcome. The view is reconstructed from scratch every time its state changes. (Not really, as there's some efficient diffing under the hood, but it's a good mental model to use.)

The simplest way that SwiftUI provides is the @State property wrapper, so a version of what you're asking for would look something like this:

struct RootView: View {
    @State private var numberOfRects = 0

    var body: some View {
        VStack {
            Button(action: {
                self.numberOfRects += 1
            }) {
                Text("Tap to create")
            }
            ForEach(0 ..< numberOfRects, id: \.self) { _ in
                MyRectView()
            }
        }
    }
}

I'm guessing your desired end result is more complicated than that, but you can use @State or use a property pointing to a separate class that handles your state/model, marked with the @ObservedObject wrapper, to get to whatever you need.

answered Apr 8, 2020 at 23:14

Brock Batsell

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1 Comment

Neo42 Over a year ago

this is a good solution, even for adding something later

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