FutureProvider的用例 [英] Use case for FutureProvider

问题描述

我想知道FutureProvider类有什么用例?

I was wondering what use case exists for the FutureProvider class?

当使用FutureProvider，ChangeNotifierProvider或类似的东西构建ui时，如何加载像Future<Contact> getAllContacts() async { ... }这样的异步函数特别使我感兴趣.

I am particularly interested how to load an asynchronous function like Future<Contact> getAllContacts() async { ... } when the ui is built with a FutureProvider, ChangeNotifierProvider or anything similar.

此外，每次调用notifyListeners()时，我都希望该提供程序通过异步调用来重建ui.提供程序有什么可能的方式还是我错过了什么?

Moreover, each time when notifyListeners() is called, I would like to have that provider to rebuild the ui with asynchronous call. Is that any way possible with provider or am I missing something?

推荐答案

FutureProvider不带有内置的更新机制，但可以与Consumer和可变对象(ChangeNotifer或State)来处理更新.

FutureProvider doesn't come with a built-in update mechanism – but can be combined with Consumer and a mutable object (ChangeNotifer or State) to handle updates.

它有两个主要用法:

• 公开需要异步加载的不可变值"(例如配置文件):

FutureProvider<MyConfig>(
  builder: (_) async {
    final json = await // TODO load json from something;
    return MyConfig.fromJson(json); 
  }
)

• 或者，它可以与可以变异的东西(例如ChangeNotifier)结合使用，以将Future转换为更易于操纵的东西:
  • Alternatively, it can be combined with something that can mutate (like ChangeNotifier) to convert a Future into something easier to manipulate:

  ChangeNotifierProvider(
    builder: (_) => Foo(),
    child: Consumer<Foo>(
      builder: (_, foo, __) {
        return FutureProvider.value(
          value: foo.someFuture,
          child: ...,
        );
      },
    ),
  );
  

  这篇关于FutureProvider的用例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！