在componentWillUnmount方法中取消所有订阅和Asyncs，如何？ [英] Cancel All Subscriptions and Asyncs in the componentWillUnmount Method, how?

问题描述

由于异步方法问题，我收到错误消息。在我的终端中，我看到：

I'm getting an error message due to an async method issue. In my terminal I'm seeing:

Warning: Can't call setState (or forceUpdate) on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount method.
- node_modules/fbjs/lib/warning.js:33:20 in printWarning
- node_modules/fbjs/lib/warning.js:57:25 in warning
- node_modules/react-native/Libraries/Renderer/ReactNativeRenderer-dev.js:12196:6 in warnAboutUpdateOnUnmounted
- node_modules/react-native/Libraries/Renderer/ReactNativeRenderer-dev.js:13273:41 in scheduleWorkImpl
- node_modules/react-native/Libraries/Renderer/ReactNativeRenderer-dev.js:6224:19 in enqueueSetState
- node_modules/react/cjs/react.development.js:242:31 in setState
* router/_components/item.js:51:16 in getImage$
- node_modules/regenerator-runtime/runtime.js:62:44 in tryCatch
- node_modules/regenerator-runtime/runtime.js:296:30 in invoke
- ... 13 more stack frames from framework internals

我注意到它特别指出了 getImage $

I noticed it's specifically pointing out the getImage$

以下是我在该部分使用的代码：

Here's the code I'm using for that section:

export default class extends Component {
    constructor(props) {
        super(props);
        const { item } = props

        const bindThese = { item }
        this.boundActionCreators = bindActionCreators(bindThese)

        this.state = {
            image: require('../../static/logo.png'),
            ready: false,
            showOptions: this.props.showOptions
        }

        this.getImage = this.getImage.bind(this)
        this.renderNotAdmin = this.renderNotAdmin.bind(this)
        this.renderAdmin = this.renderAdmin.bind(this)
        this.handleOutOfStock = this.handleOutOfStock.bind(this)
    }

    async getImage(img) {
        let imgUri = await Amplify.Storage.get(img)
        let uri = await CacheManager.get(imgUri).getPath()

        this.setState({
            image: { uri },
            ready: true
        })
    }

    componentDidMount() {
        this.getImage(this.props.item.image)
    }

我正在试图弄清楚如何使用 componentWillUnmount 这种异步方法。我该怎么做？

I'm trying to figure out how to use a componentWillUnmount with this async method. How do I go about it?

谢谢！

推荐答案

你可以使用 isMounted React模式来避免内存泄漏。

You can use isMounted React pattern to avoid memory leaks here.

在你的构造函数中：

constructor(props) {
    super(props);

    this._isMounted = false;
// rest of your code
}

componentDidMount() {
    this._isMounted = true;
    this._isMounted && this.getImage(this.props.item.image);

}

在 componentWillUnmount

componentWillUnmount() {
   this._isMounted = false;
}

在你身边 getImage（）

async getImage(img) {
    let imgUri = await Amplify.Storage.get(img)
    let uri = await CacheManager.get(imgUri).getPath()

    this._isMounted && this.setState({
        image: { uri },
        ready: true
    })
}

使用基于可取消承诺模式的 Axios 的推荐方法。因此，您可以在使用 cancelToken订阅卸载组件时取消任何网络呼叫。
以下是 Axios Cancellation 的资源

A recommend approach to use Axios which is based cancellable promise pattern. So you can cancel any network call while unmounting the component with it's cancelToken subscription. Here is resource for Axios Cancellation

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