[英]Sharing State Between Components
我要制作兩個組件:App和Map。 但是,當我嘗試制作新的品牌Map組件並將數據從App發送到Map組件時,我無法。
我的應用程序(默認)組件將數據保存為狀態。 當我嘗試將此狀態發送到Map組件時。 它以數據為支撐。
當然,如果我不分離它們並在App.js中編寫所有內容,那么一切都會按我的預期工作(地圖上顯示的標記)。 但是我想控制父組件中的所有狀態。
我違反基本的React規則嗎? 我該如何解決?
App.js
import React, { Component } from "react";
import "./App.css";
import Map from "./Map";
class App extends Component {
constructor(props) {
super(props);
this.state = {
locations: [],
markers: []
};
}
componentDidMount() {
fetch(
"correct_foursquare_api_url"
)
.then(response => response.json())
.then(data =>
data.response.venues.map(place => ({
id: place.id,
name: place.name,
lat: place.location.lat,
lng: place.location.lng
}))
)
.then(locations => {
this.setState({ locations });
});
}
render() {
return (
<div className="App">
<Map locations={this.state.locations} />
</div>
)
}
}
export default App;
Map.js
import React, { Component } from "react";
/* global google */
class Map extends Component {
constructor(props) {
super(props);
this.state = {
locations: [],
markers: []
};
}
componentDidMount() {
this.callMap();
}
callMap() {
window.initMap = this.initMap;
loadJS(
"api_url"
);
}
// Map
initMap = () => {
const { locations, markers } = this.state;
let map = new google.maps.Map(document.getElementById("map"), {
center: { lat: 59.4827293, lng: -83.1405355 },
zoom: 13
});
// Markers
for (var i = 0; i < locations.length; i++) {
var title = locations[i].name;
var position = new google.maps.LatLng(locations[i].lat, locations[i].lng);
var id = locations[i].id;
var marker = new google.maps.Marker({
map: map,
position: position,
title: title,
animation: google.maps.Animation.DROP,
id: id
});
markers.push(marker);
}
};
render() {
return <div id="map" />;
}
}
function loadJS(src) {
var ref = window.document.getElementsByTagName("script")[0];
var script = window.document.createElement("script");
script.src = src;
script.async = true;
ref.parentNode.insertBefore(script, ref);
}
export default Map;
您將locations
存儲在App
組件的狀態下,但是在安裝時也使用了處於Map
組件狀態的locations
。
相反,您可以等待渲染Map
組件,直到完成locations
請求,然后使用從App
傳遞來的Map
組件中的locations
道具。
例
class App extends Component {
constructor(props) {
super(props);
this.state = {
locations: [],
markers: []
};
}
componentDidMount() {
fetch("correct_foursquare_api_url")
.then(response => response.json())
.then(data => {
const locations = data.response.venues.map(place => ({
id: place.id,
name: place.name,
lat: place.location.lat,
lng: place.location.lng
}));
this.setState({ locations });
});
}
render() {
const { locations, markers } = this.state;
if (locations.length === 0) {
return null;
}
return (
<div className="App">
<Map locations={locations} markers={markers} />
</div>
);
}
}
class Map extends Component {
// ...
initMap = () => {
const { locations, markers } = this.props;
// ...
};
// ...
}
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