The error message "Property 'then' is not available on type 'void' within Ionic 2" is displayed

Question

The error message "Property 'then' is not available on type 'void' within Ionic 2" is displayed

When retrieving data from the Google API within the function of the details.ts file, I have set up a service as shown below. However, I am encountering a Typescript error stating

Property 'then' does not exist on type 'void'

.

this.typeApi.getTypeDetails(baseUrl).then(data => {
});

In the type-api.service.ts file, I am fetching data from the Google API in the following manner:

import { Injectable } from '@angular/core';
import { Http /*, Response*/ } from '@angular/http';
import 'rxjs/Rx';
import { Observable } from 'rxjs/Observable';

@Injectable()
export class TypeApi {

constructor(public http: Http ) {}

getTypeDetails(PlaceUrl){
        this.http
        .get(PlaceUrl)
        .map(res => res.json())
        .subscribe(
            (data) => data,
            (err) =>  err); // Handle if fails
}

}

And in the package.json file:

"dependencies": {
"@angular/common": "2.4.8",
"@angular/compiler": "2.4.8",
"@angular/compiler-cli": "2.4.8",
"@angular/core": "2.4.8",
"@angular/forms": "2.4.8",
"@angular/http": "2.4.8",
"@angular/platform-browser": "2.4.8",
"@angular/platform-browser-dynamic": "2.4.8",
"@angular/platform-server": "2.4.8",
"@ionic-native/core": "3.1.0",
"@ionic-native/geolocation": "^3.4.4",
"@ionic-native/launch-navigator": "^3.4.4",
"@ionic-native/splash-screen": "3.1.0",
"@ionic-native/status-bar": "3.1.0",
"@ionic/storage": "2.0.0",
"font-awesome": "^4.7.0",
"ionic-angular": "2.3.0",
"ionic2-rating": "^1.2.0",
"ionicons": "3.0.0",
"rxjs": "5.0.1",
"sw-toolbox": "3.4.0",
"zone.js": "0.7.2"
  },
"devDependencies": {
"@ionic/app-scripts": "1.1.4",
"typescript": "2.0.9"
},

angular typescript ionic2

Answer 1

Answer №1

To ensure proper execution, it is recommended to return a Promise from the method getTypeDetails, as shown below:

getTypeDetails(PlaceUrl){
    return this.http
        .get(PlaceUrl)
        .map(res => res.json())
        .toPromise();
}

However, returning just the Observable is often considered the more efficient approach:

getTypeDetails(PlaceUrl){
    return this.http
        .get(PlaceUrl)
        .map(res => res.json());
}

Then, use the following code snippet to subscribe to the data:

this.typeApi.getTypeDetails(baseUrl).subscribe(data => {
});

Answer 2

To ensure proper execution, it is recommended to return a Promise from the method getTypeDetails, as shown below:

getTypeDetails(PlaceUrl){
    return this.http
        .get(PlaceUrl)
        .map(res => res.json())
        .toPromise();
}

However, returning just the Observable is often considered the more efficient approach:

getTypeDetails(PlaceUrl){
    return this.http
        .get(PlaceUrl)
        .map(res => res.json());
}

Then, use the following code snippet to subscribe to the data:

this.typeApi.getTypeDetails(baseUrl).subscribe(data => {
});

Answer 3

Answer №2

I agree with Gunter's suggestion. Additionally, I recommend setting the method (function) return type whenever possible to indicate the type of result the caller will receive. For example:

Assuming that your TypeApi will be used by multiple callers.

public getTypeDetails(apiUrl: string) : Observable<any>{
       return this.http.get(apiUrl)
          .map(res => res.json())
          .catch((error) => this.handleError(error)); 
}

//Here is an example of the handleError function:

private handleError (error: any) {
    // You could delve deeper into the error for a more detailed message or utilize a remote logging system
    let errMsg = (error.message) ? error.message : error.status ? `${error.status} - ${error.statusText}` : 'Server error';
    console.error(errMsg); // log errors to the console
    return Observable.throw(errMsg);
  }

When calling this method, you must subscribe to the returned result:

this.typeApi.getTypeDetails(theUrl).subscribe(result => {
    // This is where you handle success, similar to handling success in AJAX calls
    // Make use of the received data
   }, 
   error => {
       // This is where you handle errors, similar to how errors are handled in AJAX calls
       // Handle the error appropriately
   }
);

Answer 4

I agree with Gunter's suggestion. Additionally, I recommend setting the method (function) return type whenever possible to indicate the type of result the caller will receive. For example:

Assuming that your TypeApi will be used by multiple callers.

public getTypeDetails(apiUrl: string) : Observable<any>{
       return this.http.get(apiUrl)
          .map(res => res.json())
          .catch((error) => this.handleError(error)); 
}

//Here is an example of the handleError function:

private handleError (error: any) {
    // You could delve deeper into the error for a more detailed message or utilize a remote logging system
    let errMsg = (error.message) ? error.message : error.status ? `${error.status} - ${error.statusText}` : 'Server error';
    console.error(errMsg); // log errors to the console
    return Observable.throw(errMsg);
  }

When calling this method, you must subscribe to the returned result:

this.typeApi.getTypeDetails(theUrl).subscribe(result => {
    // This is where you handle success, similar to handling success in AJAX calls
    // Make use of the received data
   }, 
   error => {
       // This is where you handle errors, similar to how errors are handled in AJAX calls
       // Handle the error appropriately
   }
);

The error message "Property 'then' is not available on type 'void' within Ionic 2" is displayed

Answer №1

Answer №2

Similar questions

Exploring the functionality of multiple checkboxes in Next.js 14, the zod library, shadcn/ui components, and react-hook

Having difficulty leveraging npm modules in TypeScript

Retrieve data from FileReader's onload event asynchronously in Javascript

What is the best way to adjust the output size for ngx-webcam?

What TypeScript syntax is similar to Java's "? extends MyClass" when using generics?

Is it possible to transmit fixed routing information utilizing a path that can be customized with parameters?

Leveraging Services in Classes Outside of Angular's Scope

"Encountered a problem while trying to follow the AngularJS2 Quickstart Guide - received error 404 stating that 'angular' is not found in

Press the text in a React Native TypeScript component to trigger a render

How can you customize the color of the arrows in Carousel Bootstrap?

Is there a way to display my modal separately from my sidenav while utilizing :host in Angular?

Experience the mesmerizing motion of a D3.js Bar Chart as it ascends from the bottom to the top. Feel free to

Tips for incorporating attributes into a customized Material-UI props component using TypeScript in React

The module "install-npm-version" could not be located

TypeScript class that utilizes internal functions to implement another class

Is it possible to activate ionViewWill/DidEnter from a tab navigating to an external page in Ionic/Angular?

What is the best way to access the activated route's data directly within the HTML template that houses the RouterOutlet?

The correct way to update component state when handling an onChange event in React using Typescript

When an empty array is returned from a catch statement in an async/await method, TypeScript infers it as never

Using Typescript: A guide on including imported images in the output directory