Angular 4: How to call catch and callback function in it to handle error. Arrow function, manage errors in get or post services.
Angular 4: How to call catch and callback function in it to handle error
Angular 4: how to redirect if API returns an error?
How to manage errors in get or post services
Need to import
import { Router } from ‘@angular/router’;
import { Observable } from ‘rxjs/Rx’;
Need to mention router in constructor
constructor(private router: Router, private http: Http) {}
Sometimes when you call catch without using arrow function like below
getUserList() {
return this.http.get(this.constURL + ‘/loans/all’, this.headerOptions)
.catch(this.handleError);
}
handleError(error: Response) {
if (error.status == 500) {
this.router.navigate([‘/login’]);
} else {
return Observable.throw(error);
}
}
Then it gives error of
ERROR TypeError: Cannot read property ‘navigate’ of undefined not getting this
Because in handleError function this object is not accessible. If you console this.router then you will get undefined.
So this object not working and not getting router all available methods
So you have to use arrow function here like below
getUserList() {
return this.http.get(this.constURL + ‘/loans/all’, this.headerOptions)
.catch(error => {
return this.handleError(error);
});
}
handleError(error: Response) {
if (error.status == 500) {
this.router.navigate([‘/login’]);
} else {
return Observable.throw(error);
}
}
Also if you have not mentioned return for handlerError function then it will throw error again like
Argument of type ‘(error: any) => void’ is not assignable to parameter of type
So it’s necessary to type return for handlerError function.
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Thanks for your input.
I tried to post easy way of handling errors.
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