Typescript interface

Question

I have a typescript interface:

export interface LatLng {
  constructor(lat: number, lng: number): void;
  lat(): number;
  lng(): number;
}

And array with a type of LatLng:

path: Array<LatLng>;

How can i push elements to this array ?

Do you actually have a class like that? Where is the implementation of this constructor? — Nitzan Tomer
– Nitzan Tomer, Commented Sep 19, 2017 at 13:31
No implementation. How can I implement this interface in class ? — Azimbek Makhmudov
– Azimbek Makhmudov, Commented Sep 19, 2017 at 13:58

alexKhymenko · Accepted Answer · 2017-09-19 16:42:16Z

2

Implement interface

export class LatLngNew implements LatLng {
 constructor(public lat: number, public lng: number) {}
}

You can write like this

this.path.push(new LatLngNew(2,3))

Also you can define array type like this

path: LatLng[];

edited Sep 19, 2017 at 16:42

answered Sep 19, 2017 at 13:27

alexKhymenko

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Comments

Nitzan Tomer · Accepted Answer · 2017-09-19 14:03:13Z

1

If you only have an interface then you should not have the constructor there and it should look like this:

export interface LatLng {
    lat(): number;
    lng(): number;
}

You can then push a new item like so:

path.push({
    lat: function() { return 0; },
    lng: function() { return 0; },
});

You can also create a factory function for it:

function createLatLng(lat: number, lng: number): LatLng {
    return {
        lat: function() { return lat; },
        lng: function() { return lng; }
    };
}

If you want a class then you do it like so:

class LatLng {
    constructor(private _lat: number, private _lng: number) {}

    lat() {
        return this._lat;
    }

    lng() {
        return this._lng;
    }
}

And push a new instance like so:

path.push(new LatLng(0, 0));

answered Sep 19, 2017 at 14:03

Nitzan Tomer

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4 Comments

Azimbek Makhmudov Over a year ago

I did't create this interface. angular-maps.com/api-docs/agm-core/interfaces/…. But I need to use this interface as a type and give elements.

Nitzan Tomer Over a year ago

Oh, it's an existing library, ok then the implementation probably already exists and you are only talking about the types. The other answer by @alexKhymenko should work for you then

Azimbek Makhmudov Over a year ago

Answer by @alexKhymenko doesn't work. It shows error: '''LatLng' only refers to a type, but is being used as a value here."

Nitzan Tomer Over a year ago

You'll need to edit your question and add more of your code, how you use this type and so on

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