A guide to implementing angularjs app.service and $q in typescript

Question

A guide to implementing angularjs app.service and $q in typescript

I am fairly new to TypeScript and AngularJS and I am struggling to find the correct answer for my issue. Below is the relevant code snippet:

export class SidenavController {
static $inject = ['$scope', '$mdSidenav'];
     constructor(private $scope: any,private $mdSidenav: any) {

     }
toggleSidenav(name: string) {
    this.$mdSidenav(name).toggle();
     }
  loadHelpInfo() {
    this.helpService.loadAll()
      .then(function(help) {
        this.$scope.helpInfo = [].concat(help);
        this.$scope.selected = this.$scope.helpInfo[0];
      })
  }
  selectHelpInfo(help) {
    this.$scope.selected = angular.isNumber(help) ? this.$scope.helpInfo[help] : help;
    this.$scope.toggleSidenav('left');
  } 

}
app.service('helpService', ['$q', function($q) {
  var helpInfo = [{
      name: 'Introduction',
      content: '1 '
  }, {
      name: 'Glossary',
      content: '2'
  }, {
      name: 'Log In',
      content: '3'
      }, {
      name: 'Home Page',
      content: '4'
  }];

  return {
      loadAll: function() {
          return $q.when(helpInfo);
      }
  };
}]);

While working on the above code, I encountered an error message: app/components/sidenav/sidenav-controller.ts(10,10): error TS2339: Property 'helpService' does not exist on type 'SidenavController'. I'm unsure on how to properly utilize services in TypeScript. If needed, I have also created a CodePen version of the Angular application:

http://codepen.io/snehav27/pen/JdNvBV

Essentially, I am attempting to convert the given code snippet into TypeScript version.

angularjs typescript angular-material

Answer 1

Answer №1

To properly utilize the helpservice, you must inject it and set it in your constructor argument.

     static $inject = ['$scope', '$mdSidenav', 'helpService'];
     constructor(private $scope: any, private $mdSidenav: any, private helpService: any) {

     }

If you fail to do so, Typescript will not recognize this.helpService, leading to errors like "cannot access loadAll of undefined" when trying to use this.helpService.loadAll.

It is also recommended to use the Arrow operator for proper lexical scoping of this.

  this.helpService.loadAll()
  .then((help) => {
    this.$scope.helpInfo = [].concat(help);
    this.$scope.selected = this.$scope.helpInfo[0];
  });

Failure to use the Arrow operator may result in errors as this won't refer to the controller instance within the callback.

Create a typing for helpService for better usage and typo reduction.

export interface IHelpService{
  loadAll(): ng.IPromise<Array<HelpInfo>>; 
}

export interface HelpInfo{
  name: string;
  content: string;
}

class HelpService implements IHelpService{
  
  // Implementation details

}

angular.module('HelpApp').service('helpService', HelpService);

Update the constructor with the correct typing for helpService.

constructor(private $scope: any, private $mdSidenav: any, private helpService: IHelpService) {

Consider using controller as syntax with Typescript class definition and avoiding attaching properties to scope for cleaner code organization.


// Example implementation of SidenavController

In your view, reference properties and methods prefixed with vm.

<body layout="column" ng-controller="AppCtrl as vm">

<--- some code -->

 <md-button ng-click="vm.selectHelpInfo(it)" 
            ng-class="{'selected' : it === vm.selected }">

Answer 2

To properly utilize the helpservice, you must inject it and set it in your constructor argument.

     static $inject = ['$scope', '$mdSidenav', 'helpService'];
     constructor(private $scope: any, private $mdSidenav: any, private helpService: any) {

     }

If you fail to do so, Typescript will not recognize this.helpService, leading to errors like "cannot access loadAll of undefined" when trying to use this.helpService.loadAll.

It is also recommended to use the Arrow operator for proper lexical scoping of this.

  this.helpService.loadAll()
  .then((help) => {
    this.$scope.helpInfo = [].concat(help);
    this.$scope.selected = this.$scope.helpInfo[0];
  });

Failure to use the Arrow operator may result in errors as this won't refer to the controller instance within the callback.

Create a typing for helpService for better usage and typo reduction.

export interface IHelpService{
  loadAll(): ng.IPromise<Array<HelpInfo>>; 
}

export interface HelpInfo{
  name: string;
  content: string;
}

class HelpService implements IHelpService{
  
  // Implementation details

}

angular.module('HelpApp').service('helpService', HelpService);

Update the constructor with the correct typing for helpService.

constructor(private $scope: any, private $mdSidenav: any, private helpService: IHelpService) {

Consider using controller as syntax with Typescript class definition and avoiding attaching properties to scope for cleaner code organization.


// Example implementation of SidenavController

In your view, reference properties and methods prefixed with vm.

<body layout="column" ng-controller="AppCtrl as vm">

<--- some code -->

 <md-button ng-click="vm.selectHelpInfo(it)" 
            ng-class="{'selected' : it === vm.selected }">

A guide to implementing angularjs app.service and $q in typescript

Answer №1

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