All:
I am pretty new to Redux, when I follow its Reddit API example, there is one code snippet confuse me so much:
In AsyncApp.js, there is:
componentDidMount() {
const { dispatch, selectedSubreddit } = this.props
dispatch(fetchPostsIfNeeded(selectedSubreddit))
}
I wonder where the dispatch and selectedSubreddit get bind to this.props?
Thanks
That example is using the connect() function from react-redux to inject certain parts of the Redux state and the store's dispatch() function as props in that component. See the 'Usage With React' part of the Redux docs for more information.
For example:
App.js:
export class App extends Component {
//...
}
function mapStateToProps(state) {
const { selectedReddit, postsByReddit } = state
const {
isFetching,
lastUpdated,
items: posts
} = postsByReddit[selectedReddit] || {
isFetching: true,
items: []
}
return {
selectedReddit,
posts,
isFetching,
lastUpdated
}
}
export default connect(mapStateToProps)(App)
The connect() function here is taking the mapStateToProps() function above to inject the appropriate parts of the Redux state as props in the <App /> component. The keys of the object returned by mapStateToProps() correspond to the names of the props injected, and the corresponding values are the values of those injected props.
connect() can also take a second argument, matchDispatchToProps(), which can be used to inject specific action dispatch functions as props in your component. Whether or not you supply any arguments to connect(), it will inject your Redux store's dispatch() function as a prop called dispatch.
These connected container components receive state updates from the store, so when your Redux state changes, the connected container components will receive new props accordingly.
Related
Good day,
The beginnings of learning redux can be confusing
The steps in this code:
Create reducer for increment
Create Store
If user takes onClick action, function increment dispatch previously mentioned reducer
In this same component display data
Render component inside Provider with store
In this case need is saving the state with data to LocalStorage.
What should I do for save counter_state to local-storage?
// reducer
function counter(state=0, action) {
console.log('counter', action)
switch(action.type) {
case 'INCREMENT':
return state + 1;
return state;
}
}
///create store
const store = createStore(counter);
// React Component
class Counter extends React.Component {
increment() {
this.props.dispatch({
type: 'INCREMENT'
});
}
render() {
return (
<div>
{this.props.state}
<div>
<button onClick={this.increment.bind(this)}>+</button>
</div>
</div>
)
}
}
const mapStateToProps = function (state) {
return {state};
}
const CounterApp = connect(mapStateToProps)(Counter);
class Test5 extends React.Component {
render() {
return (
<Provider store={store}>
<CounterApp />
</Provider>
)
}
}
export default Test5;
localStorage has a pretty simple interface. I'd recommend looking up its API on mdn. Since you're not using any of the persistence libraries you're importing, might as well try it directly for learning purposes:
Write the value of state.counter to localStorage in your mapStateToProps
When you do createStore you can pass a second argument with preloadedState. So before you do that, read from localStorage to get the saved value of your counter.
Some remarks:
state in the reducer is usually an object with properties. It might work with a simple number, but if you want to learn redux you'll want to use an object here.
I'd recommend to move on to the more complicated libraries like redux-persist once you feel comfortable with the basics of redux. It's too much abstraction at once for getting a simple counter to work.
I'm using react-redux & redux-thunk for my project.
I have to inject my actions to a component by using connect.
connect([mapStateToProps], [mapDispatchToProps], [mergeProps], [options])
My task is one level up. I don't want just to inject multiple actions in this form:
{
doThis(),
doThat()
}
But in this form:
{
this: {
doThis1(),
doThis2()
}
that: {
doThat()
}
}
So basically my problem is that I want to dispatch multiple action-creator files because I want them organized as such.
I tried this version which obviously doesn't work because dispatch is not injected in each Thunk Action Creator:
import * as actions from './actions'
const mapDispatchToProps = (dispatch) => {
return {
dataActions: {
...actions.dataActions
}
};
}
export default connect(null, mapDispatchToProps)(Component);
So my final question is:
Am I even supposed to use Redux this way? Can I organize my files this way, if so how?
If instead of having one property per action creator, you want to structure your bound action creators in a couple of properties that each contain a group of action creators, you can do something like this:
import { bindActionCreators, .. } from 'redux';
..
const mapDispatchToProps = (dispatch) => {
return {
dataActions: bindActionCreators(actions.dataActions, dispatch),
otherActions: bindActionCreators(actions.otherActions, dispatch),
..
};
};
The first argument to bindActionCreators is an object containing action-creator functions (e.g. an imported module that exports only action creators). In your actual component, you should then be able to use this.props.dataActions.someDataAction(..).
If the question is just about whether you can keep different action creators in different files, you might not even want to group the action creators and just do this:
return {
...bindActionCreators(actionCreatorsFromOneModule, dispatch),
...bindActionCreators(actionCreatorsFromAnotherModule, dispatch),
..
};
I have the following reducer:
const selectEntityReducer = function(entityState, action) {
const selectedEntity = entityState.allEntities.filter(e => (e.id == action.id))[0]
const newStateForSelectEntity = updateObject(entityState, {selectedEntity: selectedEntity});
return newStateForSelectEntity;
};
entityState shape looks like {entities:[{id:1}, {id:2}], selectedEntity:{id:2}}.
I have a React component that is connected to the store like this:
function mapStateToProps(state) {
return {
selectEntity: state.entities.selectEntity
};
}
However, it never re-renders.
If I say selectEntities: state.entities in mapStateToProps, then the component re-renders. But I'm only interested in the selected entity for this component.
I'm aware that enforcing immutability down the entire state tree is required for redux to function properly. But I thought that is what I was doing in selectEntityReducer.
Any extra context can be seen in the full redux code in this gist.
Its happens because you filter old piece of state.
You must copy your entities:
const newEntities = entityState.allEntities.slice();
const newSelectedentities = newEntities.filter.........
Copy piece of ctate if it array and then process it.
Basic Problem
I've got a Redux store with the following data:
foo: {
currentId: 1,
things: [{id: 1}, {id: 2}),
}
I'd like to make a utility method somewhere (eg. on a Foo singleton object) such that any module in my code can do:
import Foo from 'foo';
foo.getCurrentFoo(); // returns foo.thins[foo.currentId];
but I'm having trouble figuring out where to put it.
Failed Attempt
My initial attempt was to create a Foo component singleton:
// Foo.js
class FooBase extends React.Component {
getCurrentFoo() {
return this.state.foo.things[this.state.foo.currentId];
}
}
const Foor = connect((state) => state.foo)(FooBase);
export default new FooWrapper();
But that doesn't work. Redux complaieds about the property store not existing (when I did new FooWrapper()). That makes sense, because my component isn't inside a <Provider />. However, I just want a stand-alone utility class/object, not something actually in the DOM, which rules out <Provider/>.
How can I make a method like the one described above, that actually works, without involving <Provider /> ... and where do I put it?
The nice thing about the react-redux helpers is that they allow you to use connect() and <Provider /> to automatically pass the store to child components via React's context. However, that doesn't necessarily mean that you have to use these helpers, especially in areas of a codebase that don't use React.
So here lies the problem: connect() and <Provider /> help us by giving our React components access to a singleton instance of a store, but how can we access this store somewhere where connect() and <Provider /> can't be used?
I think the easiest solution here is to create a singleton class that holds on to the store, so any non-React module can still use the store.
So let's say you're creating your store like this:
init.js
import {createStore} from 'redux';
const initialState = {
currentId: 1,
things: ['foo', 'bar']
};
const reducer = (state = initialState, action) => {
if (action.type === 'SET_CURRENT_ID') {
return Object.assign({}, state, {
currentId: action.id
});
}
return state;
};
const store = createStore(reducer);
This store takes an action of type SET_CURRENT_ID which simply returns a new state with the currentId property changed to whatever was handed to it. You could then get the current "thing" by doing something like store.getState().things[store.getState().currentId]. So let's create a Singleton class that can hold on to the store and provide a wrapper around this functionality.
store.js
class Store {
constructor() {
this._store = undefined;
}
setStore(store) {
this._store = store;
}
getCurrentThing() {
if (this._store) {
const {things, currentId} = this._store.getState();
return things[currentId];
}
}
setCurrentThing(id) {
if (this._store) {
const action = {
type: 'SET_CURRENT_ID',
id
};
this._store.dispatch(action);
}
}
}
export let singletonStore = new Store();
This class creates an instance the first time it is used, and uses that instance every subsequent time. So when you originally create your store, simply import this class and call setStore().
init.js
import {singletonStore} from './store';
singletonStore.setStore(store);
Then, every subsequent file where singletonStore is used will have the same state.
test.js
import {singletonStore} from './store';
console.log(singletonStore.getCurrentThing()); // 'bar'
singletonStore.setCurrentThing(0);
console.log(singletonStore.getCurrentThing()); // 'foo'
This should work just fine for your need to use your store in modules that don't have the benefit of being passed the store magically with connect() and <Provider />.
I'm trying to build keyboard shortcut support into my React/Redux app in an idiomatic React/Redux way. The way I am planning to do this is to have the following action creator and associated action:
registerShortcut(keyCode, actionCreatorFuncReference)
The reducer would then update a registeredShortcuts object in the redux store with a mapping of keyCodes to actionCreatorFuncReferences. Then my root component would listen for keyup and see if there is an associated keyCode registered and if so, then dispatch the mapped action via the action creator function reference.
However, this would be the first time I am storing function references in my Redux store. To date, I've only had objects with keys with vanilla values (strings, ints, etc).
The Redux docs says:
You should do your best to keep the state serializable. Don’t put anything inside it that you can’t easily turn into JSON.
Does this suggest it's a bad idea to store such function references in my Redux store? If so, what is a better way to accomplish what I'm trying to do in React/Redux?
An alternative approach is just to store the mapping of keyCodes and function references in the root react component itself, but that didn't feel very Redux-like since now the application state is not in the Redux store.
No, you should not store function references in the redux store. They are not serializable, and as you mentioned state should be serializable at all times. The most redux-friendly approach I can think of is just to keep the map of hotkeys to their actionCreatorFuncNames.
TL;DR: You don't. The store state must be serializable at all times (as Nathan answered).
The Redux way is via enhancers, or the Redux-Observable way via dependencies.
NL;PR: Based on the Redux docs example, what you want is to pass the reference in your action(1), ignore it your reducer(2) and use it in your enhancer(3):
//... in your action:
const data={val:1}, ref=()=>{};
const action = {type:'ACTION_WITH_REF', data, ref}; //(1)
//... in your reducer:
case 'ACTION_WITH_REF':
return {...state, data: action.data}; //(2)
//... and in your enhancer:
import { createStore, applyMiddleware } from 'redux';
import reducers from './reducers';
export const myRefStore= {};
function refHandler({ getState }) {
return next => action => {
switch(action.type){
// this can be done more elegantly with a redux-observable
case 'ACTION_WITH_REF':
myRefStore.aRef = action.ref; // (3)
break;
}
// be sure to maintain the chain of the store
const returnValue = next(action);
// otherwise, your midddeware will break the store
return returnValue;
};
}
const store = createStore(
reducers,
initialState,
applyMiddleware(refHandler)
);
Note: As far as there are no side-effects in your enhancers, you are good to go. Be aware that you could have obtained the refs directly in the reducers, but such an approach keeps the reference at the reducer-level and misses the point of combineReducers(). With an enhancer, you keep them all in one place(myRefStore).
One final observation is that a redux store is not an any-data store but a state store, thus why we need to handle functions and other non-state related stuff in enhancers. You can leverage the enhancer backbone to Redux-Observable and inject myRefStore via dependencies.
I'm new to redux, but the way I see it, you could pass the key code and an action type.
Then a reducer could be listening for that action type and make changes accordingly.
Here is an example using the library Mousetrap:
// On your Container
function registerShortcut(element, dispatch, keyCode, actionType) {
Mousetrap(element).bind(keyCode, function(e) {
dispatch({
type: actionType,
payload: {
keyCode: keyCode,
event: e
}
});
});
});
mapDispatchToProps = function(dispatch) {
return {
onMount: function(element) {
registerShortcut(element, dispatch, ['command+f', 'ctrl+f'], 'OPEN_SEARCH');
},
onUnmount: function(element) {
Mousetrap(element).unbind(['command+f', 'ctrl+f']);
}
};
};
// On your Component
componentDidMount() {
onMount(ReactDOM.findDOMNode(this));
};
componentWillUnmount() {
onUnmount(ReactDOM.findDOMNode(this));
};
// On your reducer
function reducer(oldState, action) {
if (action.type == 'OPEN_SEARCH') {
//... make changes ...//
return newState;
}
return oldState;
};
This way, keyboard shortcuts will dispatch an action. The reducer will make the changes necessary to the state. And finally, the application can re-render.