我正在生产应用程序中首次设置ContextApi,希望用它替换我们当前对app配置的处理。我已经关注了官方文档并咨询了其他人在使用API时遇到的类似问题,并且在我使用Config.Consumer和渲染函数中的回调时,我能够正确地进行配置。但是,我无法使this.context返回除空对象之外的任何内容。
理想情况下,我会在生命周期方法中使用this.context并避免回调地狱,所以请帮助。我已经仔细检查了我的React版本,并且我正在设置contextType。下面是代码的表示
config.js
import { createContext } from "react";
export default createContext();
index.js
import React from "react";
import ReactDOM from "react-dom";
import { Provider } from "react-redux";
import { Router, browserHistory } from "react-router";
import { syncHistoryWithStore } from "react-router-redux";
import Config from "../somePath/config";
// more imports
function init() {
const config = getConfig();
const routes = getRoutes(config);
const history = syncHistoryWithStore(browserHistory, appStore);
ReactDOM.render(
<Provider store={appStore}>
<Config.Provider value={config}>
<Router history={history} routes={routes} />
</Config.Provider>
</Provider>,
document.getElementById("app")
);
}
init();
someNestedComponent.js
import React, { Component } from "react";
import { connect } from "react-redux";
import Config from "../somePath/config";
@connect(
state => ({
someState: state.someState,
})
)
class someNestedComponent extends Component {
componentDidMount() {
console.log(this.context);
}
render() {
return (...someJSX);
}
}
someNestedComponent.contextType = Config;
export default someNestedComponent;
目前正在运行:
问题是someNestedComponent
没有提到使用this.context
的类:
someNestedComponent.contextType = Config;
它指的是包装原始类的功能组件,因为它是用@connect
装饰器装饰的,它是以下的语法糖:
const someNestedComponent = connect(...)(class someNestedComponent extends Component {
...
});
someNestedComponent.contextType = Config;
相反,它应该是:
@connect(...)
class someNestedComponent extends Component {
static contextType = Config;
componentDidMount() {
console.log(this.context);
}
...
}
上下文API没有回调地狱问题;使用与React Redux中使用的相同的高阶组件模式可以方便地解决这个问题,并且还可以从装饰器语法中受益:
const withConfig = Comp => props => (
<Config.Consumer>{config => <Comp config={config} {...props} />}</Config.Consumer>
);
@connect(...)
@withConfig
class someNestedComponent extends Component {
componentDidMount() {
console.log(this.props.config);
}
...
}
您没有使用consumer
来获取值