Xcode 13.1 SwiftUI App Name "Builder"

File List:

Folder "Builder"

• BuilderApp.swift
• ContentView.swift
• FormView.swift
• Assets

Folder "Preview Content"

• Preview Assets

FUNCTION I am making a form that user interacts with TextField, Toggle, and other elements.

PROBLEM My FormView.swift file won't preview when I set the variables to bindings. I get a "missing arguments for parameters" error when I try to preview on canvas.

File 'ContentView.swift'

import SwiftUI

struct ContentView: View {

    @State private var variableOne = false

File 'FormView.swift'

import Foundation
import SwiftUI

struct FormView: View {
    @Binding var variableOne: Bool

FormView.swift A form view is used to allow user to interact with a toggle that sets 'variableOne'. This was working in preview when the variable was local.

File 'FormView.swift' The following struct reports the error "missing arguments for parameters".

struct FormView_Previews: PreviewProvider {

    static var previews: some View {
        FormView()
    }
}

I tried:

struct FormView_Previews: PreviewProvider {

    static var previews: some View {
        FormView(dangerToSelf: .constant(true), dangerToOthers: .constant(true), gravelyDisabled: .constant(true))
    }
}

I also tried:

struct FormView_Previews: PreviewProvider {

    static var previews: some View {
        FormView(variableOne: $variableOne)
    }
}

I tried a bunch of others things and I've read as much on the issue as I can. I can't seem to fix this. It seems related to the variables being changed to bindings. I want to call different forms in different swift files from within ContentView.

Thanks for guidance and help.

struct ContentView: View {

    @State private var variableOne = false

    var body: some View {

    FormView(variableOne: $variableOne)

    }
}

struct FormView: View {
    @Binding var variableOne: Bool

    var body: some View {
        Text("Test")
    }
}

Is this what you are trying to achieve? I assume you want to call FormView in ContentView?

Thanks for replying!

I do intend to call it from contentview and I have no issue with the bindings, etc. What I want is to be able to preview formview while I create it.

Because the app has many sections I wanted to call them in contentview so it doesn't have all the code in one file.

The formview preview code is what is giving me problems.

This should work.

struct FormView_Previews: PreviewProvider {
  static var previews: some View {
    FormView(variableOne: .constant(true))
  }
}

Related observation:

This week I was watching @twostraw's recent tutorials for Day 58 of 100 Days of SwiftUI.

Day 58 CoreData Dynamic Filtering

@5:50 Paul creates a Struct and adds a var parameter named "fetchRequest". XCode immediately complains that he did not provide a value for this new var for the Preview. He gets the same message that you did, "Missing argument for parameter...."

I got out my 100 Days of SwiftUI notebook and was ready to write down the secret sauce. Namely I wondered how he was going to provide a fake management object context and a fake fetchRequest to his PreviewProvider. These are not trivial types. These are heavy duty CoreData behemoths.

@twostraws continues the lecture for another four minutes before addressing the Preview error.

In the end he simply says, "the preview is not required here, so it's safe to ZAP it."

DENIED! Ouch! I was hoping he'd reveal the secret. But in the end, it might have been a bit too much for this already long-ish tutorial.

The dangerToSelf and dangerToOthers references were original from my code and I forgot to adapt it to a more understandable name, my bad.

Hatsushira, thanks for the solution, I read/saw some things on this and it didnt work for me but I'm going to try yours out and trust what others have said about your solution.

Obelix, I gave you the solution because you really made it easier to understand. I was seeking a solution but you helped me understand the problem in a deeper way.

Hope this post helps others.

Thanks to everyone who took time to read and reply!