title: React undefined this in function
body: <p>someone can explain to me why this value in the renderInput function is undefined. I browse the code and everything looks good. </p>
  
  <p>Here is error</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'renderError' of undefined
  </code></pre>
  
  <p>This is my component AddCatalog. When it calls console.log(this) in renderInput, this returns me undefinded</p>
  
  <pre><code>import React, {PropTypes} from "react";
      import {Field, reduxForm} from "redux-form";
      //
      class AddCatalog extends React.Component {
          constructor(props) {
              super(props);
              this.renderError = this.renderError.bind(this);
          }
          renderError({error, touched}) {
              alert("asds");
              if (touched &amp;&amp; error) {
                  return &lt;div className="red"&gt;{error}&lt;/div&gt;;
              }
          }
          renderInput({input, label, meta}) {
              return (
                  &lt;div className="form-group"&gt;
                      &lt;label&gt;{label}&lt;/label&gt;
                      &lt;input {...input} className="form-control" autoComplete="off" /&gt;
                      {this.renderError}
                  &lt;/div&gt;
              );
          }
          onSubmit(formValues) {
              console.log(formValues);
          }
          render() {
              return (
                  &lt;form onSubmit={this.props.handleSubmit(this.onSubmit)}&gt;
                      &lt;div className="row paddingLR30 container-fluid"&gt;
                          &lt;div className="col-12"&gt;
                              &lt;h2&gt;Dane placówki&lt;/h2&gt;
                          &lt;/div&gt;
                          &lt;div className="col-3"&gt;
                              &lt;Field label="Nazwa placówki*" name="name_kindergarten" component={this.renderInput} /&gt;
                          &lt;/div&gt;
                      &lt;/div&gt;
                      &lt;button&gt;Submit&lt;/button&gt;
                  &lt;/form&gt;
              );
          }
      }
  
      const validate = (formValues) =&gt; {
          const errors = {};
          if (!formValues.name_kindergarten) {
              errors.name_kindergarten = "Musisz podać nazwę przedszkola";
          }
          return errors;
      };
  
      export default reduxForm({
          form: "simple",
          validate
      })(AddCatalog);
  </code></pre>