Access State inside of mapDispatchToProps method

问题

I have written a container component using redux and my implementation for mapDispathToProps looks like this

const mapDispatchToProps = (dispatch, ownProps) => {
    return {
        onChange: (newValue) => {
            dispatch(updateAttributeSelection('genre', newValue));
            dispatch(getTableData(newValue, ownProps.currentYear));
        }
    }
}

The problem is that in order to getTableData i need the state of some other components. How can I get access to the state object in this method?

回答1:

You can use redux-thunk to create a separate action creator function which has access to getState, rather than defining the function inside mapDispatchToProps:

function doTableActions(newValue, currentYear) {
    return (dispatch, getState) => {
        dispatch(updateAttributeSelection('genre', newValue));
        let state = getState();
        // do some logic based on state, and then:
        dispatch(getTableData(newValue, currentYear));
    }
}


let mapDispatchToProps = (dispatch, ownProps) => {
    return {
        onChange : (newValue) => {
            dispatch(doTableActions(newValue, ownProps.currentYear))
        }
    }
}

Some varying ways to go about organizing those, but something like that ought to work.

回答2:

Possible approach is also to use mergeProps that merges mapState and mapDispatch and allows to use both at the same time.

// Define mapState
const mapState = (state) => ({
  needeedValue: state.neededValue
})

// Define mapDispatch
const mapDispatch = (dispatch, ownProps) => {
  return {
    onChange: (newValue, neededValue) => {
      dispatch(updateAttributeSelection('genre', newValue));
      dispatch(getTableData(newValue, ownProps.currentYear, neededValue));
    }
  }
}

// Merge it all (create final props to be passed)
const mergeProps = (stateProps, dispatchProps, ownProps) => {
  return {
    ...stateProps,  // optional
    ...dispatchProps,  // optional
    onChangeWithNeededValue: (newValue) => (
      dispatchProps.onChange(
        newValue,
        stateProps.needeedValue  // <<< here the magic happens
      )
    )
  }
}

// Pass mergePros to connect
const MyContainer = connect(mapState, mapDispatch, mergeProps)(MyComponent);

Official documentation: react-redux#connect

Possible performance drawback on larger apps: Stack Overflow - Performances and mergeProps in Redux

回答3:

You can just use redux-thunk to get state. Write a helper function like this:

const getState = (dispatch) => new Promise((resolve) => {
  dispatch((dispatch, getState) => {resolve(getState())})
})

You can use this in a async function or generator function:

const mapDispatchToProps = (dispatch, ownProps) => {
  return {
    async someFunction() {
      const state = await getState(dispatch)
      ...
    }
  }
}

回答4:

You can try to use:

redux-named-reducers

Which allows you to get state anywhere in your code like so:

const localState1 = getState(reducerA.state1)
const localState2 = getState(reducerB.state2)

Likewise in mapDispatchToProps:

const mapDispatchToProps = dispatch => {
  return {
    onClick: () => {
      dispatch(someAction(getState(moduleA.state1)));
    }
  };
};

回答5:

If you have used Thunk Middleware then you can write helper function into your Action.Js

export const getSearchedText =  () => (dispatch, getState) => {
    const { app } = getState();
    return app.searchedText;
}

If you have been used the container design pattern, your property container should be below

Container.js

export const mapDispatchToProps = (dispatch, ownProps) => {
    return {
             setSearch: search => {
                 var searchedText = dispatch(getSearchedText());
             }
}

来源：https://stackoverflow.com/questions/35836290/access-state-inside-of-mapdispatchtoprops-method

标签

redux

react-redux