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如何在Elixir Phoenix中获取通道消息以更改React组件的状态?

phoenix-channels phoenix-framework elixir reactjs

Thomas Browne · 技术社区 · 8 年前

我试图找出如何根据外部事件更新组件的状态,在本例中,外部事件是一条来自Elixir Phoenix频道的消息。

a) 如何将通道引入组件?到目前为止,我是作为道具通过海峡的。

b) 如何处理进入组件内部通道的消息?我的“this.state.chan.on”不起作用,看起来很笨拙。

import socket from "./socket"
import React from "react"
import ReactDOM from "react-dom"

socket.connect()

// Now that you are connected, you can join channels with a topic:
let channel = socket.channel("topic:subtopic", {})

channel.join()
  .receive("ok", resp => { console.log("Joined successfully", resp) })
  .receive("error", resp => { console.log("Unable to join", resp) })

class HelloWorld extends React.Component {
  state = {
    chan: this.props.channel,
    mess: this.props.message
  }

  this.state.chan.on("new_message", payload => {
    this.setState(prevstate => {
      return {mess: ${payload.body}}
    });
  })


  componentDidMount = () => {
    console.log("did mount Hello World")
  }

  render = () => {
    return (<h1>{this.state.mess}</h1>)
  }
}


ReactDOM.render(
  <HelloWorld message={1} channel={channel}/>,
  document.getElementById("hello-world")
)

编辑:

17:55:13 - error: Compiling of web/static/js/app.js failed. L40:6 Unexpected token 
     38 |   }
     39 | 
   > 40 |   this.state.chan.on(
        |       ^
     41 | 
     42 |   componentDidMount = () => {
     43 |     console.log("did mount Hello World")
Stack trace was suppressed. Run with `LOGGY_STACKS=1` to see the trace. 
18:07:20 - error: Compiling of web/static/js/app.js failed. L40:6 Unexpected token 
     38 |   }
     39 | 
   > 40 |   this.state.chan.on("new_message", payload => {
        |       ^
     41 |     this.setState(prevstate => {
     42 |       return {mess: ${payload.body}}
     43 |     });
Stack trace was suppressed. Run with `LOGGY_STACKS=1` to see the trace. 
18:07:22 - error: Compiling of web/static/js/app.js failed. L40:6 Unexpected token 
     38 |   }
     39 | 
   > 40 |   this.state.chan.on("new_message", payload => {
        |       ^
     41 |     this.setState(prevstate => {
     42 |       return {mess: ${payload.body}}
     43 |     });
Stack trace was suppressed. Run with `LOGGY_STACKS=1` to see the trace.

1 回复 | 直到 8 年前

Dogbert 8 年前

你不能有 this.state.chan.on(...) 在类体之外的函数。不过,您可以将所有这些代码放在构造函数中。此外,您的 setState

class HelloWorld extends React.Component {
  constructor(props) {
    super();

    this.state = {
      chan: props.channel,
      mess: props.message
    };

    this.state.chan.on("new_message", payload => {
      this.setState({mess: payload.body});
    });
  }

  ...
}

不过,这有一个问题。这个 on 即使该组件从DOM中卸载,回调也会一直被触发。您应该在中订阅邮件 componentDidMount componentWillUnmount :

class HelloWorld extends React.Component {
  constructor(props) {
    super();

    this.state = {
      chan: props.channel,
      mess: props.message
    };
  }

  componentDidMount() {
    const ref = this.state.chan.on("new_message", payload => {
      this.setState({mess: payload.body});
    });
    this.setState({ref: ref});
  }

  componentWillUnmount() {
    this.state.chan.off("new_message", this.state.ref);
  }

  ...
}