Angular, Typescript, problem with this in method

Question

I have a code like this:

myMethod(data: any, layerId: string, dataSubstrings): void {
    someObject.on('click', function(e) {
        this.api.getSomething(a).subscribe((result: any) => { // WRONG CALL 1. It is from another component
            // code
            this.outSideMethod(a)); // WRONG CALL 2

            }
        }, (error: any) => {
            return {};
        })
    });


outSideMethod(a): any[] {
    //etc
}

I need to call this.api.getSomething(a)); (and also outSideMethod()) but I get `Cannot read property 'getSomething' of undefined.

I don't know my problem using this (POO), could someone give me some hints please.

could you please share your api class snippet as well, I think your api class don't have any method defined as getSomething(). — Divyanshu Rawat, Jun 06 '19 at 22:03

score 1 · Answer 1 · answered Jun 06 '19 at 22:00

Your context object (the one pointed by the keyword this) has no api property set, so you cannot execute the getSomething method.

Check the logic about the 'this' keyword behaviour https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this because it depends on the way to invoke the method.

In angular, if you are injecting this dependency add the scope modifier (private for example) to the parameter of the constructor to bind to an internal property so you can access to it with 'this'

score -1 · Accepted Answer · answered Jun 06 '19 at 21:56

-1

try changing the function to lamda expression .

someObject.on('click', function(e) {} )

to

someObject.on('click', (e) =>{});

answered Jun 06 '19 at 21:56

Vishnu

897
6
13

Please explain why this will work! – Randy Casburn Jun 06 '19 at 21:58
Lol,I just do that, and TSLint stopped to warning me, let me see if works. – pmiranda Jun 06 '19 at 21:58
1

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions – Vishnu Jun 06 '19 at 21:59

Angular, Typescript, problem with this in method

2 Answers2