[英]Return the result value with fetch call function from another page, React native
I need to return the result of a function from another page in react native which performing a fetch call.我需要从执行 fetch 调用的 react native 中的另一个页面返回函数的结果。 I use the method as follows.
我使用的方法如下。 As I know this is because asynchronous call.
据我所知,这是因为异步调用。 Is there a special way to achieve this in react native ?
有没有一种特殊的方法可以在 react native 中实现这一点?
fetchcall.js获取调用.js
import address from '../actions/address'
const dashboard = {
getvals(){
return fetch(address.dashboardStats(),
{method: "POST",
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json',
},
body: JSON.stringify( {...
}),
})
.then((response) => response.json())
.then((responseData) => {
console.warn(responseData);
return responseData;
})
.catch((error) => { console.warn(error); })
.done();
// return 'test_val'';
}
}
export default dashboard;
dashboard.js仪表板.js
import dashboard from '../../services/dashboard';
class Dashboard extends Component {
componentDidMount(){
console.warn(dashboard.getvals());
}
}
export default connect(mapStateToProps, bindAction)(Dashboard);
Its display the result as "undefined", but that fetch call works and it displays the result.它将结果显示为“未定义”,但该 fetch 调用有效并显示结果。 Any suggestion?
有什么建议吗?
In fetchcall.js you are returning a Promise.在fetchcall.js 中,您将返回一个 Promise。 Also since you are returning the
responseData
in the .then()
method itself, you don't need the .done()
method.此外,由于您在
.then()
方法本身中返回responseData
,因此您不需要.done()
方法。
Since getvals()
is returning a Promise, you need to access it's value in a .then()
method.由于
getvals()
返回一个 Promise,您需要在.then()
方法中访问它的值。
Overall, your code should be like this:总的来说,你的代码应该是这样的:
function getvals(){ return fetch('https://jsonplaceholder.typicode.com/posts', { method: "GET", headers: { 'Accept': 'application/json', 'Content-Type': 'application/json', }, }) .then((response) => response.json()) .then((responseData) => { console.log(responseData); return responseData; }) .catch(error => console.warn(error)); } getvals().then(response => console.log(response));
The best architectural pattern, I think, is to use a callback function, usually by writing in as an anonymous function.我认为最好的架构模式是使用回调函数,通常是作为匿名函数写入。
///Component.js
my_service.login((data=>{
this.setState({body: data.body});
}));
////Service.js
export const login = function (cb){
fetch('http://myapi.com/103?_format=hal_json')
.then((response) =>{
return response.json();
})
.then((data) =>{
cb(data);
});
}
I am still a junior developer, but use this pattern frequently.我仍然是初级开发人员,但经常使用这种模式。 If someone has a reason for a different approach, I would love to hear it.
如果有人有理由采用不同的方法,我很乐意听到。
fetch always return a Promise doesn't matter what you are returning. fetch 总是返回一个 Promise 与您返回的内容无关。 so you can return a string, variable or something else but you have to use .then to access data
所以你可以返回一个字符串、变量或其他东西,但你必须使用.then来访问数据
file where you make fetch request您发出获取请求的文件
export const graphql = () => {
return fetch("https://graphqlzero.almansi.me/api", {
"method": "POST",
"headers": { "content-type": "application/json" },
"body": JSON.stringify({
query: `{
user(id: 1) {
id
name
}
}`
})
})
.then((res) => res.json()).then((responseData) => {
console.log(responseData);
return responseData;
})
}
file where you call function调用函数的文件
graphql()
.then((e) => {
console.log("data", e)
});
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