With <KMMViewModel>, how do I bind a SwiftUI TextField to a `viewModel.text` value containing the te...

# multiplatform

[Lukasz Kalnik]

With KMMViewModel, how do I bind a SwiftUI TextField to a viewModel.text value containing the text to be displayed?

[Rick Clephas]

You can use/create bindings to any mutable property with the $ sign. E.g. $viewModel.text

[Lukasz Kalnik]

But I have to mark viewModel.text as @State for this, right?

[Lukasz Kalnik]

Hmm, in my data model viewModel.text is a val, because the uiState gets copied everytime

[Lukasz Kalnik]

Actually the state is in a data class

data class UiState(
    val text: String,
    //... other properties
)

[Rick Clephas]

So what does your text property in the viewmodel look like?

[Lukasz Kalnik]

Sorry, I should have been more specific.
The viewModel emits uiState, the uiState contains the text property.

[Rick Clephas]

So to get the value you would have to call viewModel.uiState.text correct?

[Lukasz Kalnik]

Yes

[Lukasz Kalnik]

image.png

[Rick Clephas]

Hmm in that case I don't think there is a built-in way to get a binding. A generic way to get a binding isn't straightforward either since it would have to call the copy function with the correct parameter.

[Lukasz Kalnik]

OK

[Lukasz Kalnik]

I worked around this by creating a local var transactionId annotated with @State and assigning to it viewModel.uiState.transactionId

[Rick Clephas]

Yeah that would work for SwiftUI. But any updates to the value wouldn't be accessible by the viewmodel or other code outside the view.

[Rick Clephas]

This is an interesting challenge. I might take a better look at it later to see if a generic approach is doable

[Lukasz Kalnik]

Thank you for your quick help!

[Jacob Rhoda]

You might have to make a custom Binding that wraps your state and handles calling your method. I have to do this since I am using an MVI framework with unidirectional data flow...

[Jacob Rhoda]

Binding<String>(
  get: { viewModel.uiState.transactionId }
  set: { viewModel.setTransactionId($0) }
)

[Lukasz Kalnik]

Thank you so much!

[John O'Reilly]

Example of it here as well fwiw (though using Decompose instead of KMMViewModel in this example) https://github.com/joreilly/Confetti/blob/main/iosApp/iosApp/Sessions/SessionListView.swift

[Jacob Rhoda]

@John O'Reilly Line 71?

[John O'Reilly]

yes, exactly