Modify SwiftUI @State from a regular class function using Bindings

Question

I am trying to crate a regular class function that takes an optional Binding<Bool> as a parameter. The idea is that the function will modify the boolean to disable/enable a SwitUI View without the need for callback blocks.

The problem is that I can't find the proper way to modify the boolean from within the function.

func executeTask(inProgress: Binding<Bool>? = nil)
{
    inProgress = true // Error
    // ...
    inProgress = false // Error
}

The error:

Cannot assign to value: 'inProgress' is a 'let' constant

I also tried to mimic SwiftUI behavior by creating a @Binding var inProgress: Bool in the class, assign it, and then modify it with no luck.

Also I would be OK with a non-optional 'inProgress' if that helps, but so far it doesn't.

Mohammad Rahchamani · Accepted Answer · 2020-09-09 17:15:37Z

1

To change the Binding's value, you should assign the new value to its wrappedValue property.

try this:

func executeTask(inProgress: Binding<Bool>? = nil)
{
    inProgress?.wrappedValue = true
}

edited Sep 9, 2020 at 17:15

answered Sep 9, 2020 at 16:32

Mohammad Rahchamani

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Asperi · Accepted Answer · 2020-09-09 17:06:11Z

1

Binding is a special wrapper, which gives access to references stored value via .wrappedValue

Here is fixed variant (tested with Xcode 12)

func executeTask(inProgress: Binding<Bool>? = nil) {
    // optional chain
    inProgress?.wrappedValue = true
}

answered Sep 9, 2020 at 17:06

Asperi

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