Calculate.swift

/*
If you've ever wished you could calculate or evaluate something inside your #SwiftUI view's body without repeating yourself, try this pseudo-view helper.
You can now compute multiple values in tuples, call helper functions or print debug expressions.
*/

struct Calculate<Content: View, Value>: View {
    let calculation: () -> Value
    let content: (Value) -> Content

    init(
        _ calculation: @autoclosure @escaping () -> Value,
        @ViewBuilder content: @escaping (Value) -> Content
    ) {
        self.calculation = calculation
        self.content = content
    }

    var body: some View {
        content(calculation())
    }
}

struct ContentView: View {
    var body: some View {
        GeometryReader { geometry in
            Calculate(geometry.size.width / 3) { radius in
                Circle().frame(width: radius)
            }
        }
    }
}