javascript - 尝试将 onChange 函数作为 props 传递给 GrandChlidren 结果导致 TypeError : this is undefined

Question

我试图将父级的 onChange 函数传递给 grandChild 但出现错误

类型错误:这是未定义的

代码如下

var Tablefortask = React.createClass({

                            getInitialState: function() {
                                      return {data: []};

                              },
                              onChange: function (e) {

                                  var employeeId = e.target.value;
                                  alert(employeeId);

                                },

                              render: function() {

                                return (
                                 <div className="border-basic-task col-md-12">
                                 <div className="col-md-12">
                                  <table className="table table-condensed table-bordered table-striped-col " id="table-data">
                                  <thead>
                                    <tr align="center">
                                        <th>Task  Name</th>
                                        <th >Standard Discription of Task</th>
                                        <th>Employee Comment</th>
                                        <th >Employee Rating</th>
                                        <th width="30%">Reviewer Comment</th>
                                        <th >Reviewer Rating</th>
                                    </tr>
                                    </thead>
                                    <TablefortaskList data={this.state.data} onChange={this.onChange} />
                                  </table>
                                  </div>
                                  </div>
                                );
                              }
                            });

var TablefortaskList = React.createClass({
                            render: function() {
                              var commentNodes = this.props.data.map(function(comment) {
                                return (
                                  <Addcontenttotable onChange= {this.props.onChange}  taskName={comment.taskName} standarDescription={comment.standarDescription} emplComment={comment.emp_comment} empRating={comment.empRating} key={comment.id} reviewComment={comment.review_comment} reviewRating={comment.review_rating} >
                                  </Addcontenttotable>
                                );
                              });
                              return (
                                  <tbody>{commentNodes}</tbody>
                              );
                            }
                          });


                        var Addcontenttotable = React.createClass({
                              render: function() {
                              if(this.props.reviewComment=== "" && this.props.reviewRating === '' ){
                                return (
                                     <tr><td>{this.props.taskName}</td>
                                      <td>{this.props.standarDescription}</td>
                                      <td>{this.props.emplComment}</td>
                                      <td width="5%">{this.props.empRating}</td>
                                      <td ><textarea 
                                                className="form-control" 
                                                name="empComment"
                                                placeholder="Employee Comment"
                                                />
                                      </td>
                                      <td>
                                          <select  
                                                    className="form-control" 
                                                   onChange={this.props.onChange}
                                                   data-placeholder="Basic Select2 Box" >
                                                  <option value="">Option</option>
                                                  <option value="1">1</option>
                                                  <option value="2">2</option>
                                                  <option value="3">3</option>
                                                  <option value="4">4</option>
                                                  <option value="5">5</option>
                                          </select>
                                      </td>
                                  </tr>

                                );
                                }
                                else {
                                 return (
                                  <tr><td>{this.props.taskName}</td>
                                      <td>{this.props.standarDescription}</td>
                                      <td>{this.props.emplComment}</td>
                                      <td>{this.props.empRating}</td>
                                      <td>{this.props.reviewComment}</td>
                                      <td>{this.props.reviewRating}</td>
                                  </tr>
                                  );
                                }
                              }
                            });

任何见解将不胜感激

Answer 1

发生这种情况是因为this不是引用 map 函数内的组件。

要修复此问题，您必须绑定(bind)上下文，将其作为第二个参数传递给 map 函数。

 var commentNodes = this.props.data.map(function(comment) {
                                return (
                                  <Addcontenttotable onChange= {this.props.onChange}  taskName={comment.taskName} standarDescription={comment.standarDescription} emplComment={comment.emp_comment} empRating={comment.empRating} key={comment.id} reviewComment={comment.review_comment} reviewRating={comment.review_rating} >
                                  </Addcontenttotable>
                                );
                              },this);

如果您使用 ES6，您可以使用粗箭头函数来保留上下文。

 var commentNodes = this.props.data.map((comment) =>  {
                                return (
                                  <Addcontenttotable onChange= {this.props.onChange}  taskName={comment.taskName} standarDescription={comment.standarDescription} emplComment={comment.emp_comment} empRating={comment.empRating} key={comment.id} reviewComment={comment.review_comment} reviewRating={comment.review_rating} >
                                  </Addcontenttotable>
                                );
                              });

jsfiddle with the problem solved