与MobX反应(来自create-react-app)。使用axios进行异步后端API调用。重构打破初始状态
此代码有效。初始状态(问题阵列)已填充,呈现此组件的网页呈现来自状态的初始内容。
import { observable, computed, autorun, reaction } from 'mobx'
import axios from 'axios'
class IssuesStore {
@observable issues = []
constructor() {
autorun(() => console.log("Autorun:" + this.buildIssues))
reaction(
() => this.issues,
issues => console.log("Reaction: " + issues.join(", "))
)
}
getIssues(data) {
return data.map((issue) => ({title: issue.name, url: issue.url, labels: issue.labels}))
}
@computed get buildIssues() {
const authToken = 'token ' + process.env.REACT_APP_GH_OAUTH_TOKEN
axios.get(`https://api.github.com/repos/${process.env.REACT_APP_GH_USER}/gh-issues-app/issues`,
{ 'headers': {'Authorization': authToken} })
.then(response => {
console.log(response)
this.issues = this.getIssues(response.data)
return this.issues
})
.catch(function(response) {
console.log(response)
})
}
}
export default IssuesStore
在试图分开各个组件和存储API调用的承诺,我拿出了爱可信的呼叫到一个单独的js文件,作为函数的集合:
import axios from 'axios'
const authToken = 'token ' + process.env.REACT_APP_GH_OAUTH_TOKEN
export function loadIssues() {
return this.apiPromise(
`https://api.github.com/repos/${process.env.REACT_APP_GH_USER}/gh-issues-app/issues`,
{ 'headers': {'Authorization': authToken} }
)
}
export function apiPromise(endpoint, options) {
return axios.get(endpoint, options)
.then((response) => {
// console.log("response: " + JSON.stringify(response, null, 2))
return response.data.map((issue) => ({title: issue.name, url: issue.url, labels: issue.labels}))
})
.catch(function(response) {
console.log(response)
})
}
现在,我的商店看起来是这样的:
import { observable, computed, autorun, reaction } from 'mobx'
import * as github from '../api/github'
class IssuesStore {
@observable issues = []
constructor() {
autorun(() => console.log("Autorun:" + this.buildIssues))
reaction(
() => this.issues,
issues => console.log("Reaction: " + issues.join(", "))
)
}
@computed get buildIssues() {
this.issues = github.loadIssues().data
return this.issues
}
}
export default IssuesStore
小得多......但由于它现在看到的issues
作为初始状态的网页现在抛出一个错误0在第一次渲染。
Uncaught TypeError: Cannot read property 'map' of undefined
的承诺成功完成以后(因为它应该),但那时已经太晚了。当然,我可以在我的渲染组件中设置几个null
检查,以便在空的或尚未定义的变量上不运行.map
或其他此类函数。
但是为什么代码在重构之前没有初始渲染错误,而不是在之后工作?我认为重构实际上保持了相同的逻辑流程,但我必须错过什么?
谢谢!工作。我对承诺的理解不足以理解为什么我需要另一个'.then()'在返回的承诺来获取我的数据。我认为承诺中定义的'.then()'足以在响应中获取我需要的内容。 – changingrainbows