get promise value in react component

Question

I have a helper function in my component. When I console.log(helperFunction()) it, I get this in the console.

When I try to add the helper func

Answer 1

When dealing with a value that the render method will be using and is also retrieved asynchronously you should be having that value exist in the state of the component and take advantage of the componentDidMount lifecycle method to retrieve the value.

class SomeComponent extends React.component {
  constructor() {
    super();

    this.state = {
      projectName: ''
    }
  }

  componentDidMount() {
    // fetch the project name, once it retrieves resolve the promsie and update the state. 
    this.getProjectName().then(result => this.setState({
      projectName: result
    }))
  }

  getProjectName() {
    // replace with whatever your api logic is.
    return api.call.something()
  }


  render() {

    return (
      <input type="text" defaultValue={projectName}>
    )
  }
 }

you don't want to call the function and resolve the promise in the render method because render method should be a pure function based on state and props. This is a base example but should give you an idea of what needs to change. Just need to set projectName as a state variable and make and resolve the promise in the componentDidMount on the first render it will equal an empty string, once it comes back it will update to whatever the api returns.

If you don't want to show the input until the api call resolves then you can just add additional checks to see if this.state.projectName equals anything and if so render the input.

Answer 2

The problem with your code is this part.

<input ref={(input) => this.related = input} type="text" className="slds-input" defaultValue={getProjectName()} disabled/>.

The function getProjectName returns a promise, not the resolved value of that promise.

You should render your UI with render() from this.state and this.props, and if you have data that has to be loaded asynchronously, you can assign the data to i.e. this.props.relatedTo using the componentDidMount() function, something in the line of

componentDidMount() {
    var self = this;

    getProjectName()
        .then(val => {
            self.setState({relatedTo: val});
        });
}

Take a look at the state and lifecycle documentation.