react-ref-method-forwarder

Allows accessing methods of HOC-wrapped components through normal React refs

Install

npm install --save react-ref-method-forwarder

The Problem

HTML elements and React components can have methods. <input> has focus(), overflown elements have scrollTo etc. We can use refs to grab the instance and call the method:

class Field extends Component {
  focusInput() {
    this.input.focus()
  }

  render() {
    return (
      <div>
        <label>{this.props.label}</label>
        <input ref={i => (this.input = i)} />
      </div>
    )
  }
}

class App extends Component {
  render() {
    return (
      <div>
        <Field label="Name" ref={i => (this.field = i)} />
        <button onClick={() => this.field.focusInput()}>Focus</button>
      </div>
    )
  }
}

There's a problem when wrapping components with HOCs, as the ref will now point the HOC's instance:

class Field extends Component {
  focusInput() {
    this.input.focus()
  }

  render() {
    return (
      <div>
        <label>{this.props.label}</label>
        <input ref={i => (this.input = i)} />
      </div>
    )
  }
}

// this can be any HOC
const myHOC = WrappedComponent =>
  class Wrapper extends Component {
    render() {
      return <WrappedComponent {...this.props} />
    }
  }

const WrappedField = myHOC(Field)

class App extends Component {
  render() {
    return (
      <div>
        <WrappedField ref={i => (this.field = i)} />
        {/* this will fail */}
        <button onClick={() => this.field.focusInput()}>Focus</button>
      </div>
    )
  }
}

Clicking the button will throw an error, because WrappedField, is an instance of Wrapper, which does not expose focusInput.

React doesn't allow ref forwarding. When the Wrapper spreads the this.props, the original ref function that was passed in the App render method will not be forwarded to WrappedComponent.

If myHOC is under our control, we could add some ref forwarding mechanism:

const myHOC = WrappedComponent =>
  class Wrapper extends Component {
    render() {
      const { innerRef, ...props } = this.props
      return <WrappedComponent ref={innerRef} {...props} />
    }
  }

and use it with

<WrappedField innerRef={i => (this.field = i)} />

This is a bit tedious, and in case myHOC comes from a library that cannot be modified - this solution won't work.

If some component is wrapped with multiple HOCs, they all need to talk with the same API.

react-redux, for example, provides withRef option, and exposes the wrapped component with getWrappedInstance(). That may not be the case in other libraries.

So there's a need for a solution that won't require change of 3rd party packages.

The Solution / Usage

This library provides 2 HOCs: forwardMethodsInner and forwardMethodsOuter. The forwardMethodsInner HOC wraps the component with the methods, and the forwardMethodsOuter wraps the top level component. All specified methods are exposed on the result of the outer HOC.

// Field.js

// 1st step - a Component with a method
class Field extends Component {
  focusInput() {
    this.input.focus()
  }

  render() {
    return (
      <div>
        <label>{this.props.label}</label>
        <input ref={i => (this.input = i)} />
      </div>
    )
  }
}

// 2nd step - wrap it with forwardMethodsInner
const FieldWrappedWithInner = forwardMethodsInner()(Field)

// 3rd step - wrap it with any other HOCs, one or more
const FieldWrappedWithOtherHOCs = myHOC(FieldWrappedWithInner)

// 4th step - wrap FieldWrappedWithOtherHOCs with forwardMethodsOuter
// provide all the methods that need to be hoisted
const FieldWrappedWithOuter = forwardMethodsOuter({ methods: ['focusInput'] })(FieldWrappedWithOtherHOCs)

export default FieldWrappedWithOuter

// App.js

import Field from './Field'

// work with refs as if Field was never wrapped!
// focusInput is hoisted automatically

class App extends Component {
  render() {
    return (
      <div>
        <Field label="Name" ref={i => (this.field = i)} />
        <button onClick={() => this.field.focusInput()}>Focus</button>
      </div>
    )
  }
}

License

MIT © elado