[英]How to get a specific data from fetch api
我正在嘗試在我的 React Native 應用程序的<Text>
標記中獲取並顯示來自 api 的特定數據。 我要做的是從那個 api 中顯示第二個 object 的名稱。
這是我的代碼:
class HomeSreen extends Component {
constructor(props) {
super(props);
this.state = {
dataSource: [],
};
}
componentDidMount() {
const request = new Request('http://jsonplaceholder.typicode.com/users');
fetch(request)
.then(response => response.json())
.then(responseJson => {
this.setState({
dataSource: responseJson,
});
});
}
render() {
return (
<View>
<Text>Home Screen</Text>
<Text>{this.state.dataSource[1].name}</Text>
</View>
);
}
}
還有 API:
[
{
"id": 1,
"name": "Leanne Graham",
"username": "Bret",
"email": "Sincere@april.biz",
"address": {
"street": "Kulas Light",
"suite": "Apt. 556",
"city": "Gwenborough",
"zipcode": "92998-3874",
"geo": {
"lat": "-37.3159",
"lng": "81.1496"
}
},
"phone": "1-770-736-8031 x56442",
"website": "hildegard.org",
"company": {
"name": "Romaguera-Crona",
"catchPhrase": "Multi-layered client-server neural-net",
"bs": "harness real-time e-markets"
}
},
{
"id": 2,
"name": "Ervin Howell",
"username": "Antonette",
"email": "Shanna@melissa.tv",
"address": {
"street": "Victor Plains",
"suite": "Suite 879",
"city": "Wisokyburgh",
"zipcode": "90566-7771",
"geo": {
"lat": "-43.9509",
"lng": "-34.4618"
}
},
"phone": "010-692-6593 x09125",
"website": "anastasia.net",
"company": {
"name": "Deckow-Crist",
"catchPhrase": "Proactive didactic contingency",
"bs": "synergize scalable supply-chains"
}
},
.
.
.
但我無法獲得我需要的數據。 任何幫助,將不勝感激
這些數據是異步請求的,所以當第一次渲染發生時,API 沒有返回數據。
class HomeSreen extends Component {
constructor(props) {
super(props);
this.state = {
dataSource: [],
};
}
componentDidMount() {
const request = new Request('http://jsonplaceholder.typicode.com/users');
fetch(request)
.then(response => response.json())
.then(responseJson => {
this.setState({
dataSource: responseJson,
});
});
}
render() {
return (
<View>
<Text>Home Screen</Text>
{
this.state.dataSource.length === 0 ?
<Text>Waiting moment.</Text> :
<Text>{this.state.dataSource[1].name}</Text>
}
</View>
);
}
}
進行這些更改后,您可以可視化所需的數據。
如果問題是您的組件在請求完成后沒有更新該屬性,那是因為您正在對dataSource
數組進行“淺合並”,因此 React 無法檢測到數據的更改。 有幾種方法可以處理它:
fetch(request)
.then(response => response.json())
.then(responseJson => {
this.setState(prevState => {
return {
...prevState.dataSource,
dataSource: responseJson.map((obj, i)=>{ return {...dataSource[i], ...obj}},
}
});
});
https://reactjs.org/docs/optimizing-performance.html#shouldcomponentupdate-in-action
name
屬性拉到組件 state 的頂層class HomeSreen extends Component {
constructor(props) {
super(props);
this.state = {
dataSource: [],
screenTitle
};
}
componentDidMount() {
const request = new Request('http://jsonplaceholder.typicode.com/users');
fetch(request)
.then(response => response.json())
.then(responseJson => {
this.setState({
screenTitle: responseJson[1].name,
});
});
}
render() {
return (
<View>
<Text>Home Screen</Text>
<Text>{this.state.screenTitle}</Text>
</View>
);
}
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.