Question

获取工作正常，但是在从获取数据中推送值之后，“ title”数组中没有任何值。

    function getdata(){
    const title = [];
    const body = [];
     const url = 'https://jsonplaceholder.typicode.com/posts';
      fetch(url)
     .then(response => response.json())
     .then(data => {
        //  console.log(data)                        /*This works just fine*/
         data.forEach(posts => {
            title.push(posts.title)
            body.push(posts.body)
            })
     })
    //  const onlytentitle = title.slice(0,9);     
    //  return onlytentitle;
        return title;     
}
const titled = getdata();
console.log(titled);

Answer 1

Widget _authBuilder(context, Widget body) { final authModel = Provider.of<FAAuthModel>(context); return StreamBuilder( stream: FirebaseAuth.instance.onAuthStateChanged, builder: (context, snapshot) { authModel.user = snapshot.data; return body; }, ); }是一个异步函数，您要从获取的外部返回标题，因此您的函数将在获取请求完成之前返回标题。

尝试一下。

I/flutter (28504): ══╡ EXCEPTION CAUGHT BY FOUNDATION LIBRARY ╞════════════════════════════════════════════════════════
I/flutter (28504): The following assertion was thrown while dispatching notifications for FAAuthModel:
I/flutter (28504): setState() or markNeedsBuild() called during build.
I/flutter (28504): This _DefaultInheritedProviderScope<FAAuthModel> widget cannot be marked as needing to build because
I/flutter (28504): the framework is already in the process of building widgets.  A widget can be marked as needing to
I/flutter (28504): be built during the build phase only if one of its ancestors is currently building. This exception
I/flutter (28504): is allowed because the framework builds parent widgets before children, which means a dirty
I/flutter (28504): descendant will always be built. Otherwise, the framework might not visit this widget during this
I/flutter (28504): build phase.
I/flutter (28504): The widget on which setState() or markNeedsBuild() was called was:
I/flutter (28504):   _DefaultInheritedProviderScope<FAAuthModel>
I/flutter (28504): The widget which was currently being built when the offending call was made was:
I/flutter (28504):   StreamBuilder<FirebaseUser>
I/flutter (28504):

使用fetch

function getdata() {
  const title = [];
  const body = [];
  const url = "https://jsonplaceholder.typicode.com/posts";
  return fetch(url)
    .then(response => response.json())
    .then(data => {
      data.forEach(posts => {
        title.push(posts.title);
        body.push(posts.body);
      });
      return title;
    });

}
(async function() {
  const titled = await getdata();
  console.log(titled);
})();

无法从此函数获取值

1 个答案: