Implementing dependency injection in TypeScript within AngularJS

Question

Implementing dependency injection in TypeScript within AngularJS

I am currently in the process of transitioning a component (AngularJS 1.6) from JavaScript to TypeScript.

class NewProjectCtrl {
    price: number;

    static $inject = ['$http'];

    constructor($http) {
        let ctrl = this;
        ctrl.price = '50'; 
        ...
    }

    createProject() {
        $http.post('/api/project', ctrl.project)
        ...
    }
}

angular
    .module('app.projects-selection')
    .component('newProject', {
        templateUrl: 'app/projects-selection/components/new-project/new-project.tmpl.html',
        controller: NewProjectCtrl,
        bindings: {
            user: '<',
        }
    });

While making this migration, I encountered an issue with TypeScript where it raised an error on $http within my createProject method (Cannot find name $http). Most examples I found only showcase dependency injections within the constructor.

javascript angularjs typescript

Answer 1

Answer №1

Don't forget to include this. Once injected, make sure to utilize this.$http

Here are some styleguide tips for you:

namespace myNameSpace {

  class NewProjectCtrl {
    private static $inject = ['$http'];

    public price: number;

    constructor(private $http) {}

    createProject() {
      this.$http.post('/api/project', ctrl.project)
    }
  }

  class NewProjectComponent implements ng.IComponentOptions {
    constructor() {
      this.bindings: {
        user: '<',
      };
      this.templateUrl: 'app/projects-selection/components/new-project/new-project.tmpl.html';
      this.controller: NewProjectCtrl;
    }
  }

  angular
    .module('app.projects-selection', [])
    .component('newProject', new NewProjectCtrl());
}

Answer 2

Don't forget to include this. Once injected, make sure to utilize this.$http

Here are some styleguide tips for you:

namespace myNameSpace {

  class NewProjectCtrl {
    private static $inject = ['$http'];

    public price: number;

    constructor(private $http) {}

    createProject() {
      this.$http.post('/api/project', ctrl.project)
    }
  }

  class NewProjectComponent implements ng.IComponentOptions {
    constructor() {
      this.bindings: {
        user: '<',
      };
      this.templateUrl: 'app/projects-selection/components/new-project/new-project.tmpl.html';
      this.controller: NewProjectCtrl;
    }
  }

  angular
    .module('app.projects-selection', [])
    .component('newProject', new NewProjectCtrl());
}

Answer 3

Answer №2

When it comes to creating a class, remember that you are not just defining a function. In this case, the $http is injected into the constructor function and remains there - it does not carry over to the createProject function. To ensure access throughout the class, you should store it as an instance property:

private $http;  // It's good practice to declare it first with type hint

constructor($http) {
    this.$http = $http;
}

createProject() {
    this.$http.post('/api/project', ctrl.project)
}

In TypeScript, there is a shorthand notation for this:

constructor(private $http) {
}

createProject() {
    this.$http.post('/api/project', ctrl.project)
}

The use of let ctrl = this appears odd and may not be necessary. Refactoring your code accordingly might look like this:

class NewProjectCtrl {
    price: number = 50;

    static $inject = ['$http'];

    constructor(private $http) { }

    createProject() {
        this.$http.post('/api/project', ctrl.project);
    }
}

Answer 4

When it comes to creating a class, remember that you are not just defining a function. In this case, the $http is injected into the constructor function and remains there - it does not carry over to the createProject function. To ensure access throughout the class, you should store it as an instance property:

private $http;  // It's good practice to declare it first with type hint

constructor($http) {
    this.$http = $http;
}

createProject() {
    this.$http.post('/api/project', ctrl.project)
}

In TypeScript, there is a shorthand notation for this:

constructor(private $http) {
}

createProject() {
    this.$http.post('/api/project', ctrl.project)
}

The use of let ctrl = this appears odd and may not be necessary. Refactoring your code accordingly might look like this:

class NewProjectCtrl {
    price: number = 50;

    static $inject = ['$http'];

    constructor(private $http) { }

    createProject() {
        this.$http.post('/api/project', ctrl.project);
    }
}

Implementing dependency injection in TypeScript within AngularJS

Answer №1

Answer №2

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