I have a search form that fetches data from a api. This is that first time I am using Redux so please excuse my ignorance.
I am able to display the search results in the sidebar without using redux store.
handleSubmit(event) {
event.preventDefault()
get(`api1`, { maxContentLength: 400 })
.then((res) => {
this.setState({SearchItems: res.data})
})
}
There are few steps
Manually you can do using below methods of store object from redux'
below method will dispatch action to reducer
store.dispatch({type: 'GET_RESULTS' , payload: {}})
store.subscribe will receive all actions, you can register callbacks here.
store.getState() using this method you can access current state
you can find full documentation and examples at https://redux.js.org/basics/store example with redux is here redux with react
for react application you may use react-redux package to integrate redux which comes with Provider component with store property
with this you can import your global store object in your index.js file where you are creating App component.
With provider component set now you can use
And use Connect higher order component inside your react component to integrate redux actions to react component. Connect accepts two functions mapStateToProps and mapDispatchToProps functions as arguments and returns higher order component to which you pass your react component.
mapStateToProps functions as its name accepts global state and returns object with properties which then can be accessed from props, and similarly mapDispatchToProps accepts dispatchers to props. below is the example of react component integrated with redux using react-redux.
here is video tutorial react-redux video
Related
Currently I am working on a new page(functional component) that needs access to data from another page(class component).The data is store in the Redux store since I can display it with store.getState() in the class component. How would I access that data from the functional component?
There are several options.
You use the useSelector hook
You can wrap your component by the connect method
You can pass store by props from parent to children and call getState method
I'm learning reactjs, and I want to pass the data after the onSubmit event to another component to use the data.
For example:
in main.js file component
handleSubmit(e){
var value = this.state.name;
}
Here I want to pass the data to Data.js file
finalData(){
var answer = //value data
}
I have looked at many sources, but I didn't get a proper answer. Thank you
Use props or context to share data between components
In react you pass data between components using props.
Have a look at the documentation here:
https://reactjs.org/docs/components-and-props.html
If your components are not in close proximity in the component hierarchy you can consider using react context.
See the documentation here: https://reactjs.org/docs/context.html
There are many ways to share state in reactjs. For example:
use global state tree, such as mobx
use context, just like redux or native createContext
use common parent to pass props
use hooks API
You can try any of these methods, mobx is simple, redux is industrialized, props is a easy way to share simple private state.
In my react application the API sends some javascript function as a string
i.e. export const test=()=>{alert('Function from external source');} export const v=()=>void is sent. now I get it in my react application and as the state changes the component re-renders.
now, how can I call the testfunction in my component atcomponentDidUpdate or any other lifecycle hooks?
I am using Mobx and an observable variable get loaded by that string and as component re-renders that I can get it via props, so this is why componentDidUpdate was my first candidate
I've read this thread. What is the difference between state and props in React?
It says that props are different from states and ideally props should not be change in its component and only should be changed by its parent component.
However, mapStateToProps function in react-redux maps states in Redux to props of a React components, which is basically changing props of a React component when Redux state is changed by an Redux action.
It does not make sense to me. It seems that it should have been mapStateToStates instead and maps Redux states to states of a React component.
Am I missing something?
It says that props are different from states and ideally props should
not be change in its component and only should be changed by its
parent component.
State here refers to the internal state of the component, which the component can change internally via .setState().
However, mapStateToProps function in react-redux maps states in Redux
to props of a React components, which is basically changing props of a
React component when Redux state is changed by an Redux action.
The state here refers to the redux store, an external state. react-redux's connect method creates a HOC - higher order component (a component which is aware of the store's state changes). The HOC wraps the dumb react component, which is not aware of the store. Using mapStateToProps the HOC maps the data from the external state, and inject it to the react component via the props.
State in redux store -> mapStateToProps in HOC -> props passed to the dumb component
So the HOC is the parent, and the dumb component is the child. The parent injects new props to the child component, and the 1st assertion "props should not be change in its component and only should be changed by its parent component" is not violated.
Notes:
More info about higher order component can be found in Dan Abramov's article about Presentational and Container Components.
To understand how react-redux connect works - in the online free course, Getting Started with Redux, Dan Abramov shows how to build connect from scratch (lessons 22-29)
state here in mapStateToProps means state in ReduxStore.
It maps Redux state to ReactComponent props. It's not necessarily to map props to states, e.g. Pure Component
mapStateToProps pass state as a props to component using react-redux connect () function. Consider connect() function as wrapper component, which passes props to children.
mapStateToProps
connect (state) -----------------------> component(props)
With Relay, you create a React component as usual:
class TodoApp extends React.Component {
...
}
And then component is wrapped in a Relay container:
export default Relay.createContainer(TodoApp, {
...
});
The Relay container will fetch data using GraphQL and then update the state. This is a higher order component and this state is then passed down as props to its children.
This isn't (or doesn't appear to be) compatible with a flux implementation like Redux. Redux has a single global state object and it too has higher order components that pass props down to presentational components. So I don't see how both the Redux store and Relay containers can coexist currently.
So then how should we update state that doesn't come from the database? How is this state supposed to be managed with Relay?
While I can’t offer you an advice on using them together, technically you can definitely have several higher order components applied one after another:
class TodoApp extends React.Component {
// ...
}
TodoApp = connect(
// ...
)(TodoApp);
TodoApp = Relay.createContainer(TodoApp, {
// ...
});
export default TodoApp;
I’m not sure this makes a lot of sense, but it’s easily doable.
These things are still in discussion and the current state of Redux and Relay may not fit well together if you use a Relay container.
You can join the discussion here
I've done this as follows for a chat application:
The chat component (ChatComponent) is a dumb react component that expects all data to come as props. It also requires the redux dispatch function as a prop so it can dispatch actions when someone wants to send a new message. This is a 'private' component and is wrapped by...
ChatComponentRelay - this renders ChatComponent but is a Relay component which is also connected to the redux store. It uses one of the lifecycle methods (not the constructor) to dispatch the data received via relay into the redux store. This is the component that is used by the rest of the application, and is basically just a proxy to the underlying dumb ChatComponent. It renders ChatComponent passing in all the data in its props from the redux store, and also the redux dispatch function as well.