Reactjs component issue

Question

I have a strange issue. I am working with a list of components in a parent component. Basically I want to change one of the props and to reset all of the child components.

Here is the code I'm using to do that.

for (let i = 0; i < this.numOfNodes; i ++){
        let idNum = 'a' + i;
        this.passNodes[i] = idNum;
        let num = Math.floor(Math.random() * this.numOfMeetings);
        this.nodeMeeting[idNum] = this.meetings[num];
        let iid = this.passNodes[i];           
        this.nodes[i] = <Person infected = {false} reset = {true} id={iid} meeting={this.nodeMeeting[iid]} parentCallback = {this.callbackFunction} key={iid}/>                        
    }

    console.log(this.nodes[0])
    console.log(this.nodes)

This issue I am having, is with the two log statements at the bottom. For the first log statement, it prints the index into the list and in the props, reset is true, as I want it.

However, in the second log statement, when I print out the entire this.nodes, it seems that each of them haven't been updated as reset is still false for all the nodes.

I was wondering if I could get some help.

Селятин Исмет · Accepted Answer · 2020-07-04 16:36:29Z

Your issue most likely is being caused by the page not re-rendering, because you're not using States

Use States instead of trying to update the components like that, since the page only re-renders when you update/change the State, assignthis.nodes under the State of that component as this.state.nodes, then update the nodes with setState

Example code

export default class Component extends React.Component{
     constructor(props){
        super(props);
       
        this.state = {
            nodes: []
        }
     }

     componentDidMount = () => {
         // You can use Axios or whatever you use for getting the data from the
         // Back-End
         getNodes(nodes => {
             // If I'm not wrong you should
             // Be able to modify directly this.state.nodes array
             // Then update it with this.setState()
             // If I'm wrong then just assign it to a variable
             // Though the variable is a reference to it, so it should work without
             // Using a variable
             for(let i = 0; i < this.state.nodes.length; i++){
                 // Your code
                 let idNum = 'a' + i;
                 this.passNodes[i] = idNum;
                 let num = Math.floor(Math.random() * this.numOfMeetings);
                 this.nodeMeeting[idNum] = this.meetings[num];
                 let iid = this.passNodes[i];           
                 // Modified part this.nodes -> this.state.nodes
                 this.state.nodes[i] = <Person infected = {false} reset = {true} id={iid} meeting={this.nodeMeeting[iid]} parentCallback = {this.callbackFunction} key={iid}/>                        
             }
             // If you're using a variable to make the modifications, use that instead
             // of this.state.nodes, so it'll be like this.setState({nodes: yourVar})
             this.setState({nodes: this.state.nodes});
         });
     }
}

So basically transform this.nodes to be a State property, then update it via updating the State with setState and it will re-render the page and most likely will fix your issue.

See State and Lifecycle Documentation for more info.

Collectives™ on Stack Overflow

Reactjs component issue

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related