React Props is Not Defined

Question

I'm having trouble understanding why my props.updateBuilding is not working.

The following works when the prop is within the render method

class Buildings extends Component {
  constructor(props) {
      super(props);
  }

  componentWillMount() {
    this.props.fetchBuildings();
  }

  renderBuildings(building) {
    return (
      <div>
          <p> {building.name}</p>
      </div>
    );
  }


  render() {
    return (
      <div> 
        {this.props.buildings.map(this.renderBuildings)}
        <button type="button" className="btn btn-success" onClick={this.props.updateBuilding.bind(this, 1)}>Edit</button>
      </div>
    );
  }
}

function mapStateToProps(state) {
  return { buildings: state.buildings.all };
}
function mapDispatchToProps(dispatch){
  return bindActionCreators({ fetchBuildings, updateBuilding}, dispatch);
}

But when I put this.props.updateBuilding to the renderBuildings method like below...

  renderBuildings(building) {
    return (
      <div>
          <p> {building.name}</p>
          <button type="button" className="btn btn-success" onClick={this.props.updateBuilding.bind(this, building.id)}>Edit</button>
      </div>
    );
  }

I get the error:

Cannot read property 'props' of undefined

It seems that the prop updateBuildings cannot be read when it is inside the renderBuildings method and I'm not sure what is causing this.

Answer 1

you're miss-reading this error. props is not undefined, what is calling props is undefined, which is the this keyword. you can manually set the context of the map function by passing in a second parameter

this.props.buildings.map(this.renderBuildings, this)

or bind it inline

this.props.buildings.map(this.renderBuildings.bind(this))