React-Redux mapDispatchToProps not receiving mapStateToProps

Question

In my mapStateToProps function I set idToken and accessToken to values stored in state. This works, as I've been able to reference these values from the component. In mapDispatchToProps I try to use these props as arguments in my action. However, ownProps is an empty object. Why doesn't it have idToken and accessToken?

container:

import { connect } from 'react-redux'
import { toggleAddQuestionModal, fetchFriends } from '../actions'
import AddQuestionButtonComponent from '../components/AddQuestionButton'

const mapStateToProps = (state) => {
  auth = state.auth
  return {
    idToken: auth.token.idToken,
    accessToken: auth.profile.identities[0].accessToken,
  }
}

const mapDispatchToProps = (dispatch, ownProps) => {
  return {
    didPress: (idToken, accessToken) => {
      dispatch(toggleAddQuestionModal(true))
      dispatch(fetchFriends(ownProps.idToken, ownProps.accessToken))
    }
  }
}

AddQuestionButton = connect(
  mapStateToProps,
  mapDispatchToProps
)(AddQuestionButtonComponent)

export default AddQuestionButton

component:

'use strict';

import React, {
  Text,
  View,
  TouchableHighlight,
  PropTypes,
} from 'react-native'

import styles from './styles'

const AddQuestionButton = ({ didPress, idToken, accessToken }) => (
  <TouchableHighlight style={styles.actionButton} onPress={didPress(idToken, accessToken)}>
    <Text style={styles.actionButtonText}>+</Text>
  </TouchableHighlight>
)
AddQuestionButton.propTypes = {
  idToken: PropTypes.string.isRequired,
  accessToken: PropTypes.string.isRequired,
  didPress: PropTypes.func.isRequired,
}

export default AddQuestionButton

Why can't I access idToken and accessToken from ownProps? If this in an incorrect pattern, how should idToken and accessToken be accessed?

Thanks!

Answer 1

In mapStateToProps and mapDispatchToProps, the ownProps parameter refers to props the component receives via attributes, for example:

<AddQuestionButton isVisible={ true } />

The isVisible attribute will be passed as ownProps. In this way, you can have a component that receives some props from redux, and some props from attributes.

The connect method itself have a third parameter called mergeProps:

[mergeProps(stateProps, dispatchProps, ownProps): props] (Function): If specified, it is passed the result of mapStateToProps(), mapDispatchToProps(), and the parent props. The plain object you return from it will be passed as props to the wrapped component. You may specify this function to select a slice of the state based on props, or to bind action creators to a particular variable from props. If you omit it, Object.assign({}, ownProps, stateProps, dispatchProps) is used by default.

In the merge props, you actually get to combine all props together, as you can see in this answer by Dan Abramov to this issue:

function mapStateToProps(state, ownProps) {
  return {
    isFollowing: state.postsFollowing[ownProps.id]
  };
}

function mergeProps(stateProps, dispatchProps, ownProps) {
  const { isFollowing } = stateProps;
  const { dispatch } = dispatchProps;
  const { id } = ownProps;

  const toggle = isFollowing ?
    unfollowPostActionCreator :
    followPostActionCreator;

  return {
    ...stateProps,
    ...ownProps,
    toggleFollow: () => dispatch(toggle(id)))
  };
}

ToggleFollowButton = connect({
  mapStateToProps,
  null, // passing null instead of mapDispatchToProps will return an object with the dispatch method
  mergeProps
})(ToggleFollowButton)