Mapping an array from props in a connected React component

I have a connected React component pulling into props from Redux state.

It is getting an array of objects called plots, like this:

function mapStateToProps(state) { return { plots: state.plots.plots }; } 

I want to map some properties of plots into arrays.

Making this call inside the render method works fine:

render() { if (this.props.plots) { console.log(this.props.plots.map(a => a.variety)); }... } 

Defining this method outside the class declaration and calling it inside the render method returns undefined:

const varieties = props => { if (props.plots) { props.plots.map(a => a.variety); } }; render() { if (this.props.plots) { console.log(varieties(this.props); } } 

Anyone know what I'm missing?