Partial classes in typescript

Question

files.ts

export class ServiceUrls {
 static baseUrl: string = 'http://localhost:52949/V1/';
    static baseImageUrl: string = 'http://localhost:52949/';
}

filess1.ts

extends interface  ServiceUrls{
 static baseUrl: string = 'http://localhost:52949/V1/';
    static baseImageUrl: string = 'http://localhost:52949/';
}

How to implement partial class in typescript.How should i give reference of same class to make it work like partial class.If i give same class name in files1.ts its giving error declaration or statement expected.

Possible duplicate of How do I split a TypeScript class into multiple files? — 8eecf0d2
– 8eecf0d2, Commented Jan 23, 2018 at 23:07

Mustafah · Accepted Answer · 2021-02-24 10:04:17Z

2

I created and I'm using @partial decorator acts as a simplified syntax that may help divide functionality of a single class into multiple class files ... https://github.com/mustafah/partials

edited Feb 24, 2021 at 10:04

answered Feb 21, 2021 at 21:14

Mustafah

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Comments

Jack Wang · Accepted Answer · 2024-03-31 15:30:48Z

According to github issues, they have their concerns of not implementing the partial keyword. Therefore, you will need to write it yourself.

This task is no more than mixing prototypes. However, if you want a reliable one, you need to be very careful with method and property conflicts, also with type inference support.

I've written one and published on npm package partial_classes. You can use it by npm i partial_classes. And here is a simple method shows how to do this.

function combineClasses<T>(...constructors: T[]) {
    class CombinedClass {
        constructor(...args: any[]) {
            constructors.forEach(constructor => {
                const instance = new constructor(...args); // copy instance property
                Object.assign(this, instance);
            });
        }
    }

    constructors.forEach(constructor => { // copy prototype property
        let proto = constructor.prototype;
        while (proto !== Object.prototype) { // iterate until proto chain ends
            Object.getOwnPropertyNames(proto).forEach(name => {
                const descriptor = Object.getOwnPropertyDescriptor(proto, name);
                if (!descriptor) return;
                Object.defineProperty(CombinedClass.prototype, name, descriptor);
            });
            proto = Object.getPrototypeOf(proto);
        }
    });
    return CombinedClass
}

then use as

import combineClasses from 'partial_classes'
class ServiceUrlsFoo { }
class ServiceUrlsBar { }
const ServiceUrls = combineClasses(ServiceUrlsFoo, ServiceUrlsBar)
const instance = new ServiceUrls()

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