Variety of returns from shared functions

Question

Variety of returns from shared functions

class Parent { 
  protected info: any;
  
  getInfo(): dataTypeA | dataTypeB {
    return this.info; 
  } 
} 

class A extends Parent { 
  protected info: dataTypeA = getDataTypeA(); 
} 

class B extends Parent { 
  protected info: dataTypeB = getDataTypeB(); 
}

How can we modify the a.getInfo() and b.getInfo() methods to specifically return dataTypeA and dataTypeB respectively, instead of the current union type dataTypeA | dataTypeB, assuming that a and b are instances of classes A and B?

typescript

Answer 1

Answer №1

To allow derived classes to determine the type of data, you can utilize a type parameter in the Parent class:

class Parent<T> {
    protected data: T;

    get(): T {
        return this.data;
    }
}
class A extends Parent<dataA> {
    protected data: dataA = getDataA();
}

class B extends Parent<dataB> {
    protected data: dataB = getDataB();
}

let a = new A();
var da = a.get(); // will be dataA

let b = new B();
var db = b.get();// will be dataB

Take a look at the code in the playground.

If you want to use common members from dataA and dataB in the Parent class, you can apply a type constraint to T. This ensures that the passed type parameter has specific characteristics, allowing you to access its members within Parent:

class Parent<T extends { commonField: string } > { ... }

Answer 2

To allow derived classes to determine the type of data, you can utilize a type parameter in the Parent class:

class Parent<T> {
    protected data: T;

    get(): T {
        return this.data;
    }
}
class A extends Parent<dataA> {
    protected data: dataA = getDataA();
}

class B extends Parent<dataB> {
    protected data: dataB = getDataB();
}

let a = new A();
var da = a.get(); // will be dataA

let b = new B();
var db = b.get();// will be dataB

Take a look at the code in the playground.

If you want to use common members from dataA and dataB in the Parent class, you can apply a type constraint to T. This ensures that the passed type parameter has specific characteristics, allowing you to access its members within Parent:

class Parent<T extends { commonField: string } > { ... }

Variety of returns from shared functions

Answer №1

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