React JS - Uncaught TypeError：this.props.data.map不是函数 [英] React JS - Uncaught TypeError: this.props.data.map is not a function

问题描述

我正在使用reactjs，并且在尝试显示json数据时（无论是来自文件还是服务器）似乎无法阻止此错误：

I'm working with reactjs and cannot seem prevent this error when trying to display json data (either from file or server):

Uncaught TypeError: this.props.data.map is not a function

我看过了at：

React code throwingTypeError：this.props.data.map不是函数

React.js this.props.data.map（）不是函数

这些都没有帮助我解决问题。加载页面后，我可以验证this.data.props是不是未定义的（并且具有与json对象等效的值 - 可以使用 window.foo 调用），因此，当它被ConversationList调用时，似乎没有及时加载。如何确保 map 方法正在处理json数据而不是 undefined 变量？

Neither of these has helped me fix the problem. After my page loads, I can verify that this.data.props is not undefined (and does have a value equivalent to the json object - can call with window.foo), so it seems like it isn't loading in time when it is called by ConversationList. How do I make sure that the map method is working on the json data and not an undefined variable?

var converter = new Showdown.converter();

var Conversation = React.createClass({
  render: function() {
    var rawMarkup = converter.makeHtml(this.props.children.toString());
    return (
      <div className="conversation panel panel-default">
        <div className="panel-heading">
          <h3 className="panel-title">
            {this.props.id}
            {this.props.last_message_snippet}
            {this.props.other_user_id}
          </h3>
        </div>
        <div className="panel-body">
          <span dangerouslySetInnerHTML={{__html: rawMarkup}} />
        </div>
      </div>
    );
  }
});

var ConversationList = React.createClass({
  render: function() {

    window.foo            = this.props.data;
    var conversationNodes = this.props.data.map(function(conversation, index) {

      return (
        <Conversation id={conversation.id} key={index}>
          last_message_snippet={conversation.last_message_snippet}
          other_user_id={conversation.other_user_id}
        </Conversation>
      );
    });

    return (
      <div className="conversationList">
        {conversationNodes}
      </div>
    );
  }
});

var ConversationBox = React.createClass({
  loadConversationsFromServer: function() {
    return $.ajax({
      url: this.props.url,
      dataType: 'json',
      success: function(data) {
        this.setState({data: data});
      }.bind(this),
      error: function(xhr, status, err) {
        console.error(this.props.url, status, err.toString());
      }.bind(this)
    });
  },
  getInitialState: function() {
    return {data: []};
  },
  componentDidMount: function() {
    this.loadConversationsFromServer();
    setInterval(this.loadConversationsFromServer, this.props.pollInterval);
  },
  render: function() {
    return (
      <div className="conversationBox">
        <h1>Conversations</h1>
        <ConversationList data={this.state.data} />
      </div>
    );
  }
});

$(document).on("page:change", function() {
  var $content = $("#content");
  if ($content.length > 0) {
    React.render(
      <ConversationBox url="/conversations.json" pollInterval={20000} />,
      document.getElementById('content')
    );
  }
})

编辑：添加样本conversations.json

adding sample conversations.json

注意 - 调用 this.props.data.conversations 也会返回错误：

Note - calling this.props.data.conversations also returns an error:

var conversationNodes = this.props.data.conversations.map...

返回

未捕获的TypeError：无法读取未定义的属性map

这是conversations.json：

Here is conversations.json:

{user_has_unread_messages：false，unread_messages_count ：0，对话：[{id：18768，last_message_snippet：Lorem ipsum，other_user_id：10193}]}

{"user_has_unread_messages":false,"unread_messages_count":0,"conversations":[{"id":18768,"last_message_snippet":"Lorem ipsum","other_user_id":10193}]}

推荐答案

.map 函数仅在数组上可用。

看起来像数据不符合您期望的格式（它是{}但是你期待[]）。

The .map function is only available on array.
It looks like data isn't in the format you are expecting it to be (it is {} but you are expecting []).

this.setState({data: data});

应该是

this.setState({data: data.conversations});

检查数据的设置类型，并确保它是一个数组。

Check what type "data" is being set to, and make sure that it is an array.

修改后的代码有一些建议（propType validation和clearInterval）：

Modified code with a few recommendations (propType validation and clearInterval):

var converter = new Showdown.converter();

var Conversation = React.createClass({
  render: function() {
    var rawMarkup = converter.makeHtml(this.props.children.toString());
    return (
      <div className="conversation panel panel-default">
        <div className="panel-heading">
          <h3 className="panel-title">
            {this.props.id}
            {this.props.last_message_snippet}
            {this.props.other_user_id}
          </h3>
        </div>
        <div className="panel-body">
          <span dangerouslySetInnerHTML={{__html: rawMarkup}} />
        </div>
      </div>
    );
  }
});

var ConversationList = React.createClass({
 // Make sure this.props.data is an array
  propTypes: {
    data: React.PropTypes.array.isRequired
  },
  render: function() {

    window.foo            = this.props.data;
    var conversationNodes = this.props.data.map(function(conversation, index) {

      return (
        <Conversation id={conversation.id} key={index}>
          last_message_snippet={conversation.last_message_snippet}
          other_user_id={conversation.other_user_id}
        </Conversation>
      );
    });

    return (
      <div className="conversationList">
        {conversationNodes}
      </div>
    );
  }
});

var ConversationBox = React.createClass({
  loadConversationsFromServer: function() {
    return $.ajax({
      url: this.props.url,
      dataType: 'json',
      success: function(data) {
        this.setState({data: data.conversations});
      }.bind(this),
      error: function(xhr, status, err) {
        console.error(this.props.url, status, err.toString());
      }.bind(this)
    });
  },
  getInitialState: function() {
    return {data: []};
  },

 /* Taken from 
    https://facebook.github.io/react/docs/reusable-components.html#mixins
    clears all intervals after component is unmounted
  */
  componentWillMount: function() {
    this.intervals = [];
  },
  setInterval: function() {
    this.intervals.push(setInterval.apply(null, arguments));
  },
  componentWillUnmount: function() {
    this.intervals.map(clearInterval);
  },

  componentDidMount: function() {
    this.loadConversationsFromServer();
    this.setInterval(this.loadConversationsFromServer, this.props.pollInterval);
  },
  render: function() {
    return (
      <div className="conversationBox">
        <h1>Conversations</h1>
        <ConversationList data={this.state.data} />
      </div>
    );
  }
});

$(document).on("page:change", function() {
  var $content = $("#content");
  if ($content.length > 0) {
    React.render(
      <ConversationBox url="/conversations.json" pollInterval={20000} />,
      document.getElementById('content')
    );
  }
})

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