Question 74758 in Flutter Question posted in
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The argument type 'Future<void>' can't be assigned to the parameter type 'Future<void> Function()' – Flutter

There is a function

  Future<void> refresh({bool value = false}) async {
    changeUsers(await _service.loadUsers());
    if (value) return;
    ...
  }

in view I can use it the way

return RefreshIndicator(
    onRefresh: refresh,
    ...

but if I need to pass named parameter

return RefreshIndicator(
    onRefresh: refresh(value: true),
    ...

it gives the error

The argument type ‘Future’ can’t be assigned to the parameter
type ‘Future Function()’.

How to fix it?

Tags:

2

Answers


  1. 0

    To fix this error, you need to pass a function to the onRefresh parameter of RefreshIndicator. Currently, you are calling the refresh function and passing its result to onRefresh, which is causing the error.

    To pass a named parameter to the refresh function, you can use a lambda function or an anonymous function.

    return RefreshIndicator(
  onRefresh: () => refresh(value: true),
  ...
);
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  2. 0

    onRefresh on RefreshIndicator takes a function with the signature:

     Future<void> Function()

    But when you provide refresh(value: true), you are no longer providing a method of that signature but are instead calling your refresh function and provides the result of that call which ends up being Future<void>.

    If you want to call your method with some specific arguments, you need to provide a function to onRefresh which does that. E.g.:

    return RefreshIndicator(
    onRefresh: () => refresh(value: true),
...

    We are here providing () => refresh(value: true) as anonymous function which calls refresh(value: true) and returns whatever that call might return which here is Future<void>. Therefore this provided method fits the specified signature for onRefresh.

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