I was doing Using State in Compose "codelab" (Andr...

# getting-started

[skwalking]

I was doing Using State in Compose "codelab" (Android)
there was a code

TodoItemInlineEditor(
    item = currentlyEditing,
    onEditItemChange = onEditItemChange,
    onEditDone = onEditDone,
    onRemoveItem = { onRemoveItem(todo) }
)

In my case I wrote in this way:

TodoItemInlineEditor(
    item = currentlyEditing,
    onEditItemChange = {onEditItemChange},           ............................difference 1 writing inside {}
    onEditDone = {onEditDone},                       ............................difference 2 writing inside {}
    onRemoveItem = { onRemoveItem(todo) }
)

by using onEditItemChange and onEditDone inside {} somehow made my app to stop working. So what is the difference by writing inside {} and without {} ?
onEditItemChange , onEditDone and onRemoveItem(todo) are lamda callback from:

@Composable
fun TodoScreen(
    items: List<TodoItem>,
    currentlyEditing: TodoItem?,
    onAddItem: (TodoItem) -> Unit,
    onRemoveItem: (TodoItem) -> Unit,
    onStartEdit: (TodoItem) -> Unit,
    onEditItemChange: (TodoItem) -> Unit,
    onEditDone: () -> Unit
) {
.....
.....
TodoItemInlineEditor(
    item = currentlyEditing,
    onEditItemChange = onEditItemChange,
    onEditDone = onEditDone,
    onRemoveItem = { onRemoveItem(todo) }
)
....
....
}

[Roukanken]

a) next time you probably want to ask smth like this in #compose
but b) this one is easy without knowing compose so:

the difference is, that {} create a lambda - a new function
you have onEditItemChange: (TodoItem) -> Unit - function which takes TodoItem and returns Unit

then a onEditItemChange = {onEditItemChange} passes a function as argument, and the function takes 1 implicit parameter it (probably of type TodoItem I assume), and then returns a onEditItemChange - a function of (TodoItem) -> Unit
So whole {} expression would have type (TodoItem) -> ( (TodoItem) -> Unit) )

so either without {} (passing the function directly) or you need to actually call the function inside the lambda: onEditItemChange = { onEditItemChange(it) }