When I try and assign the output of the Toggle to an old variable it says: Binding<Bool> is not convertible to <Bool>

问题

When I try and assign the output of the Toggle to an old variable it says: Binding is not convertible to bool. Is there a way to fix this. I am coding this in Swift Playgrounds. The code below is the part which doesn't function

import SwiftUI
import PlaygroundSupport

struct ContentView : View {

    @State private var redButton = false
    @State private var step = 0
    @State private var washingHandsToggle = true
    @State private var wearingMaskToggle = true
    @State private var coverMouthToggle = true
    @State private var quarantineToggle = true
    @State private var text = ""
    @State private var slide = 20.0
    @State private var slidetwo = 500000.0
    @State private var r0 = 0
    @State private var rvalues = [6.5, 6.1, 5.3, 4.8, 4.2, 3.5, 3.1, 2.9, 1.75, 1.5, 1.2, 1.0, 0.92, 0.82, 0.75, 0.7]

    var body: some View {
        VStack {
            VStack {
                Toggle(isOn: $washingHandsToggle) {
                    Text("Washing Hands Regularly")
                }.padding(.horizontal, 50)
                    .padding(.vertical, 25)

                Toggle(isOn: $wearingMaskToggle) {
                    Text("Wearing a Protective Mask")
                }.padding(.horizontal, 50)
                    .padding(.vertical, 25)

                Toggle(isOn: $coverMouthToggle) {
                    Text("Cover Mouth When Sneezing")
                }.padding(.horizontal, 50)
                    .padding(.vertical, 25)


                Toggle(isOn: $quarantineToggle) {
                    Text("Quarantine")
                }.padding(.horizontal, 50)
                    .padding(.vertical, 25)
                    .padding(.bottom, 30)
                r0 = rvalues[(wearingMaskToggle ? 1:0) + (washingHandsToggle ? 2:0) + (quarantineToggle ? 8:0) + (coverMouthToggle ? 4:0)]

                if !washingHandsToggle && !wearingMaskToggle && !quarantineToggle {
                    Text("Select At least 1")
                }else {
                    Text("Your R") + Text("0")
                        .font(.system(size: 15.0))
                        .baselineOffset(-6.0) + Text("Value Is")


                    Text("\(r0)")

                }

回答1:

You can't just set r0 in the middle of a VStack. In general, it becomes very messy if you start writing normal statements like assignment, loops, method calls, in a function builder, like the closure argument to VStack.init.

You'd better make r0 a computed property:

var r0 : Double {
    rvalues[(wearingMaskToggle ? 1:0) + (washingHandsToggle ? 2:0) + (quarantineToggle ? 8:0) + (coverMouthToggle ? 4:0)]
}

And delete the line where you set r0.

One of the four Texts in the else branch is missing a +. You should write:

Text("Your R") +
Text("0 ")
    .font(.system(size: 15.0))
    .baselineOffset(-6.0) +
Text("Value Is ") +
Text("\(r0)")

Also, I noticed you did not include coverMouthToggle in the if statement. That might be a typo...

来源：https://stackoverflow.com/questions/61714040/when-i-try-and-assign-the-output-of-the-toggle-to-an-old-variable-it-says-bindi