CODEWITHSUNDEEP
typescript
YakovL
YakovL

Reputation: 8347

Is there a way to implicitly set properties in constructor in TypeScript?

Imagine a simple class with a basic constructor:

class Animal {
    name: string
    constructor(name: string) {
        this.name = name
    }
}

The problem about this is somewhat obvious: with a growing number of properties (age: number; type: AnimalType etc) one has to write those things thrice:

class Animal {
    name: string
    age: number
    type: AnimalType
    // ...
    constructor(name: string, age: number, type: AnimalType) {
        this.name = name
        this.age = age
        this.type = type
        // ...
    }
}

so the constructor will get bigger and bigger, and the code is not particularly DRY. Is there some standart way to avoid this in TS? I can imagine something like

class Animal {
    @Required name: string
    @Required age: number
    @Required type: AnimalType
    // ...
    constructor(anotherParam) {
        // implicitly: this.name = name
        // implicitly: this.age = age
        // implicitly: this.type = type

        // deal with anotherParam
    }
}

but the syntax is not accurate, rather to illustrate the expected result.

The only simple solution that I'm aware of is to create an interface like this:

interface AnimalPermanentParams {
    name: string
    age: number
    type: AnimalType
}

class Animal {
    permanentParams: AnimalPermanentParams
    // ...
    constructor(permanentParams: AnimalPermanentParams, anotherParam) {
        this.permanentParams = permanentParams
        // ...
    }
}

but this has an obvious drawback of an extra layer: we have to use this.permanentParams.age instead of just this.age. So are there any sane alternatives?

Upvotes: 3

Views: 1323

Answers (1)

Tobias S.
Tobias S.

Reputation: 23835

You can just declare the parameter as public (or private) and it will set the property for you.

class Animal {
    constructor(public name: string) {}
}


new Animal("abc").name

Playground

Upvotes: 4

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