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) }
)
....
....
}

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) }