CODEWITHSUNDEEP
typescript
ra00l
ra00l

Reputation: 600

Any way of saving & using this context in typescript?

I have an existing angular 1.4 application I want to port to typescript. Suppose I have the following typescript class:

class my {
  constructor(public msg: string) {     
  }

  a() {
    alert(this.msg);
  }
}

I want both the calls below to do the same thing:

var a = new my('hello');
a.a();
var fn = a.a;
fn();

However, fn doesn't work, it's losing its scope. I know I can use fat arrow syntax ( a = () => {} ) to save the scope for a single method.

I'd want a more elegant solution, to save the this scope inside a variable and always have access to it, without having to declare each of my methods with fat arrow.

UPDATE: Sorry for the ambiguity, what I am looking for is a typescript class that will output the following Javascipt (notice the _self variable and its usage):

 var my = (function () {
  var self = this;
  function my(msg) {
    self.msg = msg;
  }
  my.prototype.a = function () {
    alert(self.msg);
  };
  return my;
}());

Upvotes: 2

Views: 2217

Answers (1)

TSV
TSV

Reputation: 7641

You can use bind:

var instance = new my('hello');
instance.a(); // Call instance method
var fn = instance.a.bind(instance); // Get bound method
fn(); // Call bound method

Update 1.

What do you think about using the method to obtain bound method from class:

function getBoundMethod(instance, methodName) {
    return instance[methodName].bind(instance);
}

var instance = new my('hello');
instance.a(); // Call instance method
var fn = getBoundMethod(instance, "a"); // Get bound method
fn(); // Call bound method

Upvotes: 2

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