无法在React-redux中使用Connect访问存储

Question

I am using React in my application. I am using connect to access the store, Briefly I have this code:

class MyComponent extends Component{
   constructor(props){
        super(props)
    }

    render(){
      let components = this.props.components;
      if(components.indexOf("SomeString")){
           //some stuffs
      }
        return (
            <SomeElement/>
        )
    }
}


const mapStateToProps = state => {
    return {
        components: state.someReducer.components
    }
}

export default connect(mapStateToProps)(MyComponent)

Components is an array of strings, if I print with console.log(this.props.components) inside the render function, the I am able to see the array in the browser console. However, if I try to find a value inside that array using indexOf then I get this error:

TypeError: components is undefined

So, What am I missing? I tried many things without result

Answer 1

At first cycle, this.props.components is undefined. You can bypass it using

render(){
      if(this.props.components) {
      let components = this.props.components;
      if(components!=null || components!=undefined){ //this will check if components is null or undefined
        if(components.indexOf("SomeString")){
           //some stuffs
        }}
          return (
            <SomeElement/>
          )
    }

Answer 2

You need to check for the this.props.components like so:

render(){
      if(this.props.components) {
        let components = this.props.components;
        if(components.indexOf("SomeString")){
           //some stuffs
        }
        return (
           <SomeElement/>
        )
      } else {
           return(<div>Loading...</div>)
      }
 }