Uncaught TypeError: Cannot read property 'showBarChart' of undefined in React

问题

I have a function that customizes tooltip of nvd3 scatterChart plot. In the function I want to update state, so I am calling another function that does setState:

chart.tooltip.contentGenerator(function (d) {
      var html = "<div>";
      d.series.forEach(function(elem){
        Object.keys(data_obj).forEach(function(key_1) {
          var outer_obj = data_obj[key_1];
          if (outer_obj["key"] === elem.key) {
             // THIS FUNCTION UPDATES STATE
             this.showBarChart(elem.key);

              var expr = outer_obj["values"][0]["expr"];
              html += "<p>" + elem.key + "</p>";
              html += "<p>x = " + d.value + ", y = " + elem.value + "</p>";
          }
        });
      })
      html += "</div>";
      return html;
    }).bind(this);

Inside the constructor I have:

class ScatterChart extends React.Component {
  constructor(props){
  super(props);
  this.createScatterChart = this.createScatterChart.bind(this);
  this.showBarChart = this.showBarChart.bind(this);
  this.state = {
      neuron_name: ""
  }
}

And render:

render() {
console.log(this.state.neuron_name);
  return <div width={500} height={500}>
          <svg ref={node => this.node = node} width={500} height={500}></svg>
          <BarChart datum = { expressionDatum.getDatumForNeuron(this.state.neuron_name) }/>
        </div>
}

How could I make contentGenerator function see this object?

回答1:

I was able to set the state by assigning that = this and then accessing that:

 var that = this;
    chart.tooltip.contentGenerator(function (d) {
      var html = "<div>";
      d.series.forEach(function(elem){
        Object.keys(data_obj).forEach(function(key_1) {
          var outer_obj = data_obj[key_1];
          if (outer_obj["key"] === elem.key) {
              that.showBarChart(elem.key);
              var expr = outer_obj["values"][0]["expr"];
              html += "<p>" + elem.key + "</p>";
              html += "<p>x = " + d.value + ", y = " + elem.value + "</p>";

          }
        });
      })
      html += "</div>";
      return html;
    });

Although it lead to a weird bug when nvd3 prints tooltips like crazy, I can update the state.

来源：https://stackoverflow.com/questions/47999062/uncaught-typeerror-cannot-read-property-showbarchart-of-undefined-in-react

标签

javascript

reactjs

nvd3.js