Retrieve the values of private variables within a defined function

While experimenting with typescript, I have encountered an issue that I can't seem to resolve. My project involves using Angular, so I will present my problem within that context.

Here is a snippet of my code:

class PersonCtrl{
    private $scope: IPersonScope;
    private $http: ng.IHttpService;

    static $inject = ['$scope', '$http']
    constructor($scope: IPersonScope, $http: ng.IHttpService) {
        this.$scope = $scope;
        this.$http = $http;
        this.init();
    }

    init() : void  {
        this.$scope.fullName = 'Justin S.';
        this.$scope.buttonClick = this.buttonClick;

        console.log("-----------------Init------------------");
        console.log(this);
    }

    buttonClick(): void {
        console.log("-----------------ButtonClick------------------");
        console.log(this.$http);
    }


}

I am attempting to access the $http service when clicking a button. The buttonClick function is bound in the view, and I'm excluding the HTML code as it's not essential for this explanation.

Upon button click, my goal is to execute an AJAX call to the server. However, the issue lies in the fact that 'this' refers to the button's context in JavaScript, not the context of the PersonCtrl where I declared my private variables.

As a beginner in learning typescript, I acknowledge that there may be better approaches to solving this problem. If you have any suggestions or improvements, please feel free to share them with me.

How can I access $scope and $http within the buttonClick function?

Answer №1

Modification:

this.$scope.buttonClick = this.buttonClick;

Modify it to:

this.$scope.buttonClick = () => this.buttonClick();

This change will result in the following Javascript code that maintains the context of 'this':

let _this = this;
this.$scope.buttonClick = function() { return _this.buttonClick(); };

Answer №2

this in the buttonClick function may not behave as you initially expect. It actually refers to the scope of the method itself, rather than the controller.

To work around this issue, it's important to create a reference to this. If you're not familiar with TypeScript (in CoffeeScript, you could simply use fat arrows), the following regular JavaScript approach can be used:

private $scope: IPersonScope;
private $http: ng.IHttpService;
// declare variable for referencing 'this'
let _this;

init(): void {
  // save a reference to use in other methods
  _this = this;
  // ...
}

buttonClick(): void {
  console.log("- - ButtonClick - -");
  // now refer to the controller's 'this' using the saved reference
  console.log(_this.$http);
}

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