Strategy - string to type in typescript

Question

I'm using typescript, and I want to map a string to a type so I can make instances of certain type based on a string I have.

I'm writing to node.js

For example - I get from a DB the value "range" and for that case I want to use my class "RangeFilter", but in the case of the value "size" I want to use the class "SizeFilter". They all inherit from the interface "IFilter".

So is there a way to map (create a dictionary) between the values to the type

So it could be like this

map: {key: string, value: IFilter};

Return new map["range"] //returns RangeFilter

Possible duplicate of Dynamically loading a typescript class (reflection for typescript) — invernomuto
– invernomuto, Commented Jul 13, 2016 at 11:33
Since I'm writing to node.js I don't have window object, and I can't search inside it of my object — Shoham Ben Shitrit
– Shoham Ben Shitrit, Commented Jul 13, 2016 at 11:35
See this question on creating a TS map interface stackoverflow.com/questions/34686200/… — Chic
– Chic, Commented Jul 13, 2016 at 12:45

Nitzan Tomer · Accepted Answer · 2016-07-13 13:09:18Z

4

There is a way.
Basically all you need to know is that the type of a class MyClass is: { new(): MyClass }.

Then you can do:

interface IFilter {}

type FilterConstructor = { new(): IFilter };

class RangeFilter implements IFilter {}

class SizeFilter implements IFilter {}

let ctors: { [key: string]: FilterConstructor } = {};
ctors["range"] = RangeFilter;
ctors["size"] = SizeFilter;

function factory<T extends IFilter>(key: string): T {
    let ctor = ctors[key];

    return ctor == null ? null : new ctor() as T;
}

let rangeFilter: RangeFilter = factory("range");

(code in playground)

edited Jul 13, 2016 at 13:09

answered Jul 13, 2016 at 12:25

Nitzan Tomer

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1 Comment

Shoham Ben Shitrit Over a year ago

Thank you ! Helped a lot

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