I have a route (using React-Router) with component which it renders. Every time this route opened and its component created I need to reset some part of Redux state (one reducer's state in fact), used in this component. This reducer is shared in some other parts of the app, so I use Redux state and not local component's state. So how can I reset the reducer's state every time my component created? I am wondering about best practice to do this.
I think if I'll dispatch actions in componentDidMount method, there will be blinking of previous state for some second.
Can I dispatch action to reset some reducer's state in component's constructor?
Is there any better approach? Can I somehow to set initial state in connect() function, so component will have resetted state each time it created? I check the docs, but I cannot find some argument for this.
Yes, you can dispatch action in constructor to change reducer state
constructor(prop){
super(prop);
prop.dispatch(action);
}
Another approach you can try is setting default props so that you don't need to call reducer(dispatch action)
ButtonComponent.defaultProps = {
message: defaultValue,
};
One possible solution I can think of...
If you could go with the first approach, you can try to stop the previous state being shown while component is being re-rendered with reset state.
The only phase during which you would see the prevState is during the initial render. How about an instance variable to track the render count.
A rough draft.
import React from "react";
import { connect } from "react-redux";
import { add, reset } from "./actions";
class Topics extends React.Component {
renderCount = 0;
componentDidMount() {
// Dispatch actions to reset the redux state
// When the connected props change, component should re-render
this.props.reset();
}
render() {
this.renderCount++;
if (this.renderCount > 1) {
return (
<div>
{this.props.topics.map(topic => (
<h3 id={topic}>{topic}</h3>
))}
</div>
);
} else {
return "Initializing"; // You can return even null
}
}
}
const mapStateToProps = state => ({ topics: state });
const mapDispatchToProps = (dispatch) => {
return {
add(value){
dispatch(add(value));
},
reset(){
dispatch(reset());
}
}
}
export default connect(mapStateToProps, mapDispatchToProps)(Topics);
Here renderCount
is a class variable, that keeps incrementing on component render
. Show a fallback UI on first render to avoid previous state from being shown and on second render (due to redux store update), you could display the store data.
A working example added below. I have added an approach to avoid the fallback UI as well. Have a look if it helps.
https://stackblitz.com/edit/react-router-starter-fwxgnl?file=components%2FTopics.js
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