How am I supposed to preview composable function which invokes `viewModel()` function?

# compose

[Grigorii Yurkov]

How am I supposed to preview composable function which invokes viewModel() function?

[Mikael Alfredsson]

you shouldn’t connect them in a “hard” way.
Let your composable take a lambda with the correct signature (same as the function you want to call) and in the preview you can send in a dummy expression, while in the real usage you send in a reference to your viewmodel function.

[Mikael Alfredsson]

// function in Viewmodel
fun getText() :String {
    return "RealText"
}


// usage in real code
SomeText(textFetcher = model::getText)

@Preview
@Composable
fun previewSomeText(){
    SomeText(textFetcher = {"test text"})
}

@Composable
fun SomeText(textFetcher : ()-> String ){
    Text(text = textFetcher())
}

[Grigorii Yurkov]

Yeah, thank you, I got it

[Grigorii Yurkov]

But, I think, you gave wrong example. Why do we need lambda here.

// usage in real code
SomeText(textFetcher = viewModel.getText())

@Preview
@Composable
fun previewSomeText(){
    SomeText("test text")
}

@Composable
fun SomeText(text: String){
    Text(text = text)
}

We need lambda only for listeners

[Mikael Alfredsson]

sorry, that was just an example function, it could be a function that returns different data depending on input, then you need the lambda (I should have added an parameter to the function)

[Javier]

I had the same problem and I did previews for each state the screen can have instead of preview de entire screen composable which has the ViewModel