我实际上有两个问题。 第一件事是,使用 componentWillMount 或 componentDidMount 对用户进行检查将返回异步,因为它会转到 firebase 检查当前用户,并且 if 语句不会运行,因为没有用户。 我试图用 Promise 来解决这个问题,但也许我对 Promise 的理解并不好,所以我放弃了它,并尝试使用内部代码。 我用组件WillUpdate替换了挂载,因为它似乎运行了多次,以便我可以强制绕过错误并检查状态是否正确更改。
这就引出了我的第二个问题。 我的设置状态说未定义。 我已经阅读了堆栈溢出并尝试使用".bind(this("和胖管,但两者都不起作用。 也许我把它放在错误的地方,或者我的语法是错误的。 有人可以帮忙吗?
import React, { Component } from 'react';
import Search from './Search'
import Recipe from './Recipe'
import fire from '../fire'
//import firebase from 'firebase'
class Favourites extends Component {
constructor(props){
super(props);
this.state = {
recipes: []
}
}
componentDidUpdate() {
var user = fire.auth().currentUser;
if(user) {
console.log('Favorites: requesting favorites');
fire.database().ref('/favourites/' + user.uid).once('value').then(function (snapshot) {
var recipes_obj = snapshot.val();
let recipes = [];
for (let id in recipes_obj) {
let recipe = recipes_obj[id];
recipe.id = id;
recipes.push(recipe);
console.log("recipes: ", recipes)
}
console.log("recipes outside", recipes);
this.setState({ recipes: recipes });
});
} else {
console.log('Favorites: no user')
}
}
render() {
return(
<div>
<div className="wrapper">
<div className="container">
<div className="row">
<div className="col s12">
{console.log(this.recipes.bind(this))}
{/*{this.recipes.map( recipe => {*/}
{/*return (*/}
{/*<div key={recipe.id}>*/}
{/*{recipe.title}*/}
{/*</div>*/}
{/*)*/}
{/*})}*/}
</div>
</div>
</div>
<div className="container" id="search">
<div className="row">
<div className="col s12">
<Recipe/>
</div>
</div>
</div>
</div>
</div>
)
}
}
export default Favourites;
这是对承诺的尝试 2:
componentDidMount() {
var user = new Promise ((resolve, reject) => {
resolve(fire.auth().currentUser).then(() => {
if(user) {
console.log('Favorites: requesting favorites');
fire.database().ref('/favourites/' + user.uid).once('value').then(function (snapshot) {
var recipes_obj = snapshot.val();
let recipes = [];
for (let id in recipes_obj) {
let recipe = recipes_obj[id];
recipe.id = id;
recipes.push(recipe);
console.log("recipes: ", recipes)
}
console.log("recipes outside", recipes);
this.setState({ recipes: recipes });
}.bind(this));
} else {
console.log('Favorites: no user')
}
})
})
执行以下操作有帮助吗?(将其绑定到承诺中的函数(
fire.database().ref('/favourites/' + user.uid).once('value').then(function (snapshot) {
var recipes_obj = snapshot.val();
let recipes = [];
for (let id in recipes_obj) {
let recipe = recipes_obj[id];
recipe.id = id;
recipes.push(recipe);
console.log("recipes: ", recipes)
}
console.log("recipes outside", recipes);
this.setState({ recipes: recipes });
}.bind(this));