反应:组件属性未正确存储我想要的数据(来自查询) [英] React: An component attribute is not properly storing the data (from a query) that I want
问题描述
我最近开始学习反应,遇到了一些我不理解的事情.因此,当我声明一个组件时,我也在构造函数中声明了一个属性.然后,在执行第一个查询(我正在使用Apollo客户端-GraphQL)之后,我要将结果(我知道它将始终是电子邮件)存储在声明的属性中,以便可以将其用作第二个查询中的参数.
I recently started learning react and I have encountered something that I do not understand. So when I declare a component I also declare an attribute in the constructor. Then, after executing the first query (I am using Apollo client - GraphQL ) I want to store the result (which I know that will be always an email) in the attribute declared so I can use it as a parameter in the second query.
该应用程序的逻辑是,我想显示给定电子邮件的所有订单,但首先我得到带有查询的电子邮件.
The app logic is that I want to show all the orders of a given email, but first I get the email with a query.
这是代码:
export default class Orders extends Component {
constructor(){
super();
this.email = '';
}
render() {
return (
<div>
<Query query = { GET_MAIL_QUERY }>
{({data, loading}) => {
if (loading) return "Loading...";
this.email = data.me.email;
return <h1>{this.email}</h1>
}}
这时将返回包含电子邮件的标头,因此一切正常.但是,当我执行第二个查询(或尝试在第二个标题中显示电子邮件)时,似乎值存储不正确.
At this point a header containing the email is returned, so all good. But when I execute the second query (or try to display the email in the second header for that matter) it seems that the value is not properly stored.
</Query>
<h1>{this.email}</h1>
<Query query = { GET_ORDERS_QUERY }
variables = {{
email: this.email
}}>
{({data, loading}) => {
if (loading) return "Loading...";
console.log(data);
let orders = data.ordersByEmail.data;
console.log(orders);
return orders.map(order =>
<div>
<h1>{order.date}</h1>
<h1>{order.price}</h1>
<h1>{order.conference.conferenceName}</h1>
<h1>{order.user.email}</h1>
<br></br>
</div>)
}}
</Query>
</div>
)
}
}
const GET_MAIL_QUERY = gql`
query getMyMail{
me{
email
}
}
`;
const GET_ORDERS_QUERY = gql`
query getOrdersByEmail($email: String!) {
ordersByEmail(email: $email) {
data {
gid
date
price
user {
email
}
conference{
conferenceName
}
}
}
}
`;
我希望对此做一个解释,也可能希望找到一个解决方案(存储从查询返回的值以在另一个查询中使用)
I would love an explanation for this and maybe a solution (to store a value returned from a query to use it in another)
感谢您的期待:)
推荐答案
以我的经验,您应该使用从 @ apollo/react-hooks
导入的 useQuery
和功能组件因为它易于使用,所以可以使您的代码更简洁
In my experience, you should use useQuery
imported from @apollo/react-hooks
with functional component because it's easy to use, it makes your code more cleaner
如果您想将< Query/>
组件与类component一起使用,则可以.但是,如果要存储从服务器接收到的数据,则应在构造函数的状态下创建一个变量,并且要更新为状态时,应使用 this.setState({email:data.me.email})
.不要使用 this.state.email = data.me.email
,它是反模式,当您使用它更新状态时,React不会触发重新渲染.
If your want to use <Query/>
component with class component, it's ok. But, if you want to store data received from server, you should create a variable in state of constructor and when you want to update to state, you should use this.setState({email: data.me.email})
. Don't use this.state.email = data.me.email
, it's anti-pattern, React will not trigger re-render when you use it to update your state.
这是代码:
import React, { useState } from 'react'
import gql from 'graphql-tag'
import { useQuery, useMutation } from '@apollo/react-hooks'
const GET_MAIL_QUERY = gql`
query getMyMail {
me {
email
}
}
`
const GET_ORDERS_QUERY = gql`
query getOrdersByEmail($email: String!) {
ordersByEmail(email: $email) {
data {
gid
date
price
user {
email
}
conference {
conferenceName
}
}
}
}
`
const Orders = () => {
const [email, setEmail] = useState('')
const { data: getMailQueryData, loading, error } = useQuery(GET_MAIL_QUERY, {
onCompleted: data => {
setEmail(data.me.email)
},
onError: err => alert(err),
})
const { data: getOrdersQueryData } = useQuery(GET_ORDERS_QUERY, {
variables: { email: email },
})
if (loading) return <div>Loading...</div>
if (error) return <div>Error...</div>
return ...
}
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