Typescript - Arrow Function with Parameters

Question

I am new to Typescript, and attempting to introduce it to some of my stuff, but I am having difficulty with some scope and arrow functions.

In javascript, my code looks like this ...

var model = params.model;

model.Prototypes.bind('change', function(e){
   // some code to execute when the event occurs
   model.set([some values]); // this performs an operation to the actual top level model
});

Alright, so this has two problems. When I go to do this in Typescript, I do it like this...

class ClassName {
   model: any;

   subscribe() {
      this.model.Prototypes.bind("change", function(e){
         // FIRST PROBLEM
         this.model ....
      });
   }
}

Alright, so this works up until the labelled part. this.model is no longer a reference to what I think it is, because it is in the context of the function, not the 'class'. So I did some digging and learned I should be using an arrow function, because that will preserve the context.

The problem is, I cannot conceive of how to do an arrow function and still pass through the parameters I need, like the change value for the bind event, or the function(e) part. I have only seen examples that expect no parameters at all.

x0n · Accepted Answer · 2014-01-17 21:56:20Z

3

The arrow/lambda syntax would look like this:

class ClassName {
   model: any;

   subscribe() {
      this.model.Prototypes.bind("change", e => {
         // FIRST PROBLEM
         this.model ....
      });
   }
}

If you have more than one parameter, use this format:

(p1, p2, p3) => { ... }

Hope this helps,

answered Jan 17, 2014 at 21:56

x0n

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