Type signatures for this passed to free-standing functions

Question

Here is the code:

interface Foo
{
    c : string
}

function foo()
{
    var c = this.c
    return c
}

foo.call({ c : "quux" })

Visual Studio says that this : any so autocompletion of this.c doesn't work. How do I add a signature to tell that this implements Foo so IDE has type info for autocompletion of this. inside foo?

Answer 1

simply create a temp variable:

var self:Foo = this;
var c = self.c
return c

There is an open issue to specify what this means in an arbitrary context that you can vote/contribute to : https://typescript.codeplex.com/workitem/507

Answer 2

Since the function foo could be used with any this context, you'd need to use a type assertion:

var c = (<Foo>this).c; 

Otherwise, the signature can't be inferred.