'dispatch' is not a function when argument to mapToDispatchToProps() in Redux

If you want to use mapDispatchToProps without a mapStateToProps just use null for the first argument.

export default connect(null, mapDispatchToProps)(Start)

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You are just missing the first argument to connect, which is the mapStateToProps method. Excerpt from the Redux todo app:

const mapStateToProps = (state) => {
  return {
    todos: getVisibleTodos(state.todos, state.visibilityFilter)
  }
}

const mapDispatchToProps = (dispatch) => {
  return {
    onTodoClick: (id) => {
      dispatch(toggleTodo(id))
    }
  }
}

const VisibleTodoList = connect(
  mapStateToProps,
  mapDispatchToProps
)(TodoList)

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Use

const StartContainer = connect(null, mapDispatchToProps)(Start) 

instead of

const StartContainer = connect(mapDispatchToProps)(Start)

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I solved it by interchanging the arguments, I was using

export default connect(mapDispatchToProps, mapStateToProps)(Checkbox)

which is wrong. The mapStateToProps has to be the first argument:

export default connect(mapStateToProps, mapDispatchToProps)(Checkbox)

It sounds obvious now, but might help someone.

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I needed an example using React.Component so I am posting it:

import React from 'react';
import * as Redux from 'react-redux';

class NavigationHeader extends React.Component {

}

const mapStateToProps = function (store) {
    console.log(`mapStateToProps ${store}`);
    return {
        navigation: store.navigation
    };
};

export default Redux.connect(mapStateToProps)(NavigationHeader);

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Issue

Here are a couple of things to notice in order to understand the connected component's behavior in your code:

The Arity of connect Matters: connect(mapStateToProps, mapDispatchToProps)

React-Redux calls connect with the first argument mapStateToProps, and second argument mapDispatchToProps.

Therefore, although you've passed in your mapDispatchToProps, React-Redux in fact treats that as mapState because it is the first argument. You still get the injected onSubmit function in your component because the return of mapState is merged into your component's props. But that is not how mapDispatch is supposed to be injected.

You may use mapDispatch without defining mapState. Pass in null in place of mapState and your component will not subject to store changes.

Connected Component Receives dispatch by Default, When No mapDispatch Is Provided

Also, your component receives dispatch because it received null for its second position for mapDispatch. If you properly pass in mapDispatch, your component will not receive dispatch.

Common Practice

The above answers why the component behaved that way. Although, it is common practice that you simply pass in your action creator using mapStateToProps's object shorthand. And call that within your component's onSubmit That is:

import { setAddresses } from '../actions.js'

const Start = (props) => {
  // ... omitted
  return <div>
    {/** omitted */}
    <FlatButton 
       label='Does Not Work'
       onClick={this.props.setAddresses({
         pickup: this.refs.pickup.state.address,
         dropoff: this.refs.dropoff.state.address
       })} 
    />
  </div>
};

const mapStateToProps = { setAddresses };
export default connect(null, mapDispatchToProps)(Start)

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A pitfall some might step into that is covered by this question but isn't addressed in the answers as it is slightly different in the code structure but returns the exact same error.

This error occurs when using bindActionCreators and not passing the dispatch function

Error Code

import someComponent from './someComponent'
import { connect } from 'react-redux';
import { bindActionCreators } from 'redux'
import { someAction } from '../../../actions/someAction'

const mapStatToProps = (state) => {
    const { someState } = state.someState

    return {
        someState
    }
};

const mapDispatchToProps = (dispatch) => {
    return bindActionCreators({
        someAction
    });
};

export default connect(mapStatToProps, mapDispatchToProps)(someComponent)

Fixed Code

import someComponent from './someComponent'
import { connect } from 'react-redux';
import { bindActionCreators } from 'redux'
import { someAction } from '../../../actions/someAction'

const mapStatToProps = (state) => {
    const { someState } = state.someState

    return {
        someState
    }
};

const mapDispatchToProps = (dispatch) => {
    return bindActionCreators({
        someAction
    }, dispatch);
};

export default connect(mapStatToProps, mapDispatchToProps)(someComponent)

The function dispatch was missing in the Error code

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React-redux 'connect' function accepts two arguments first is mapStateToProps and second is mapDispatchToProps check below ex.

export default connect(mapStateToProps, mapDispatchToProps)(Index); `

If we don't want retrieve state from redux then we set null instead of mapStateToProps.

export default connect(null, mapDispatchToProps)(Index);

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You're missing in the last statement. As we don't have mapStateToProps, so the statement will be like below

const StartContainer = connect(null, mapDispatchToProps)(Start) 

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When you do not provide mapDispatchToProps as a second argument, like this:

export default connect(mapStateToProps)(Checkbox)

then you are automatically getting the dispatch to component's props, so you can just:

class SomeComp extends React.Component {
  constructor(props, context) {
    super(props, context);
  }
  componentDidMount() {
    this.props.dispatch(ACTION GOES HERE);
  }
....

without any mapDispatchToProps

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i am using like this.. its easy to understand first argument is mapStateToProps and second argument is mapDispatchToProps in the end connect with function/class.

const mapStateToProps = (state) => {
  return {
    todos: getVisibleTodos(state.todos, state.visibilityFilter)
  }
}

const mapDispatchToProps = (dispatch) => {
  return {
    onTodoClick: (id) => {
      dispatch(toggleTodo(id))
    }
  }
}

export default connect(mapStateToProps,mapDispatchToProps)(TodoList);

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Sometime this error also occur when you change the order of Component Function while passing to connect.

Incorrect Order:

export default connect(mapDispatchToProps, mapStateToProps)(TodoList);

Correct Order:

export default connect(mapStateToProps,mapDispatchToProps)(TodoList);

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I got this issue when i wrote : export default connect (mapDispatchToProps,mapStateToProps)(SearchInsectsComponent); instead of export default connect (mapStateToProps,mapDispatchToProps)(SearchInsectsComponent);

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