What is the method for declaring constructor functions as object properties in TypeScript?

Question

What is the method for declaring constructor functions as object properties in TypeScript?

I am facing a challenge with typing an object that has a property which is a constructor function. How can I properly define the type for this situation:

interface MyObj {
    constructor: () => ({ init: () => void })
}

const myObj = {
    constructor: function(this: any) {
        this.init = function() {
            this.var = 5;
        }
    }
}

Currently, I have this: any in the constructor function to prevent errors. If I remove it, I encounter the following error message:

Property 'init' does not exist on type '{ constructor: () => void; }'

Property 'var' does not exist on type '{ constructor: () => void; }'

What is the appropriate way to type constructor functions like this?

typescript

Answer 1

Answer №1

It is recommended to utilize the keyword "new" when defining the constructor function type

Refer to the example provided below:

To begin, create the interface for the constructor options

interface ObjectConfiguration<T> {
    initialize: (instance: T) => void;
}

Next, define the interface for the object

interface CustomObject<T> {
    constructor: new (config: ObjectConfiguration<T>) => T;
}

Now, proceed to implement specific instances of the custom object and a test class

class CustomObjectItem {
    public value: number;
}

const customObj: CustomObject<CustomObjectItem> = {
    constructor: CustomObjectItem
};

You can now use customObj to instantiate new objects

const initializer = (instance: CustomObjectItem) => {
    instance.value = 5;
};

const instance = new customObj.constructor({ initialize: initializer });

Answer 2

It is recommended to utilize the keyword "new" when defining the constructor function type

Refer to the example provided below:

To begin, create the interface for the constructor options

interface ObjectConfiguration<T> {
    initialize: (instance: T) => void;
}

Next, define the interface for the object

interface CustomObject<T> {
    constructor: new (config: ObjectConfiguration<T>) => T;
}

Now, proceed to implement specific instances of the custom object and a test class

class CustomObjectItem {
    public value: number;
}

const customObj: CustomObject<CustomObjectItem> = {
    constructor: CustomObjectItem
};

You can now use customObj to instantiate new objects

const initializer = (instance: CustomObjectItem) => {
    instance.value = 5;
};

const instance = new customObj.constructor({ initialize: initializer });

What is the method for declaring constructor functions as object properties in TypeScript?

Answer №1

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