CODEWITHSUNDEEP
javascriptreactjsreact-routerreact-router-dom
Erik L
Erik L

Reputation: 195

react is not recognizing params?

so in react I have an App component that is rendering several child components like this:

App

render() {
    return (
      //JSX inside
      <BrowserRouter>
        <div>
          <Header />
          <Switch>
            <Route exact path="/" component={Courses} />
            <Route exact path="/courses/create"  component={() => <CreateCourse email={this.state.emailAddress} pass={this.state.password} />} />
            <Route exact path="/courses/:id/update" component={() => <UpdateCourse email={this.state.emailAddress} pass={this.state.password} />} />
            <Route exact path="/courses/:id" component={() => <CourseDetail email={this.state.emailAddress} pass={this.state.password} />} />
            <Route exact path="/signin" component={ () => <UserSignIn signIn={this.signIn}/>} /> {/*pass in the signIn() in a prop called signIn to the UserSignIn component*/}
            <Route exact path="/signup" component={UserSignUp} />
            {/* <Route exact path="/signout" component={UserSignOut} /> */}
          </Switch>
        </div>
      </BrowserRouter>
    );
  }

In this component I have params so that I am able to see a course by its id:

CourseDetail

componentDidMount() {
    const {match: { params }} = this.props; //I used a code snippet from this video https://scotch.io/courses/using-react-router-4/route-params
    //fetch data from API
    axios
      .get(`http://localhost:5000/api/courses/${params.id}`)
      .then(results => {
        //results param came back as data from api
        this.setState({
          //set state by setting the courses array to hold the data that came from results
          course: results.data,
          user: results.data.user
        });
        //console.log(results); //By console logging I was able to see that I am getting each individual course's info in the data object
      });
  }

  //this method will be for deleting a course
  handleDelete() {
    const { match: { params }, history } = this.props;

    axios.delete(`http://localhost:5000/api/courses/${params.id}`, {
    auth: {
      username: this.props.email,
      password: this.props.pass
   }
  }).then(() => {
      history.push("/"); //I used the history object and have it push to the homepage, that way every time I delete a course I am redirected to (/) afterwards
    });
  }

the error I am getting when I try to navigate to the CourseDetail component that uses params is:

CourseDetail error

can someone help?

Upvotes: 1

Views: 990

Answers (3)

Shad
Shad

Reputation: 1219

Match is not defined because you didn't pass it down the component as props.

To do that

<Route exact path="/courses/:id/update" component={(routeProps) => <UpdateCourse email={this.state.emailAddress} pass={this.state.password} routeProps = {routeProps} />} />

you can then get your Match property via routeProps.

const {match} = this.routeProps;

Or simply use the property spread notation which will spread out the properties in routeProps as discrete properties in your component.

Example, 

<Route exact path="/courses/:id/update" component={(routeProps) => <UpdateCourse email={this.state.emailAddress} pass={this.state.password} {...routeProps} />} />

This is equivalent to writing-

<Route exact path="/courses/:id/update" component={(routeProps) => <UpdateCourse email={this.state.emailAddress} pass={this.state.password} Match = {this.routeProps.Match} Location = {this.routeProps.Location}/>} History = {this.routeProps.History />

Upvotes: 2

Code Maniac
Code Maniac

Reputation: 37775

You need to pass props like this read here 

component={props => <CourseDetail {...props} email={this.state.emailAddress} pass={this.state.password} />} />

The props passed to courseDetails component do not have any prop name match and in your componentDidMount you're doing this 

const {match: { params }} = this.props;

Here match will be undefined so you can access params

You can understand by this example

let a = {a:{b:1}}

let {x:{b,}} = a

The above code is same as below

"use strict";

var a = {
  a: {
    b: 1
  }
};
var b = a.x.b;

So eventually here if during destructuring if you don't have match as params you're trying to access

(this.props.match).params
         |
         |__________ This is undefined  you end up `undefined.params`

Upvotes: 2

Rohini
Rohini

Reputation: 254

When you write this

const {match: { params }} = this.props;

It means you are expecting props to have a match attribute like below:

params = this.props.match.params;

This is why you are getting the specified error.

If you want to assign a variable the props use this

const params = props;

Note: [If you surround a variable with bracket const {match} = props; it means you are expecting a key match in props.

Upvotes: 0

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