TypeScript passing Variables

Question

I'm brand new to typescript - having an issue with variables and scope.

I have 2 public methods, one requires a string. The first method calls the second, from within a jQuery click function (which means I can't use this.methodName anymore). I tried fixing the scope in a logical method but TS complains that:

Supplied Paramaters do not match any signature of call target. Could not select overload for 'call' expression.

    public test1() {
        //fix scope
        var scopeFix = () => this.test2;

        $("#test").click(function () {
            //this.test2("blah");
            //^^^ This doesn't work because "this." is used by jquery
            scopeFix("blah");
        });
    }

    public test2(testString:string) {
        alert(testString);
    }

I'm sure it's something silly (like me mixing JS and TS too much) - any ideas?

Use a local to store a reference to the this scope you need, jsfiddle.net/9DjGp — asawyer
– asawyer, Commented Jan 23, 2014 at 18:02
Sure, it's a common question. Nothing to do with typescript though. The typescript error is because the scopeFix function is a paramterless function that returns a function, so your call site is wrong, it should be more like fixScope()('blah'); — asawyer
– asawyer, Commented Jan 23, 2014 at 18:22

David Sherret · Accepted Answer · 2014-01-23 19:31:45Z

2

In TypeScript you can do this:

public test1() {
    $("#test").click(() => {
        this.test2("blah");
    });
}

Note the () => {} syntax. To give you an idea of what this is doing, check out the compiled JavaScript:

YourClass.prototype.test1 = function () {
    var _this = this;

    $("#test").click(function () {
        _this.test2("blah");
    });
};

edited Jan 23, 2014 at 19:31

answered Jan 23, 2014 at 19:26

David Sherret

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