Mastering TypeScript 3 - Third Edition

Specialist classes

Now for the three types of specialist classes, all derived from the Person base class:

class Infant extends Person  { 
    constructor(dateOfBirth: Date) { 
        super(dateOfBirth); 
        this.Category = PersonCategory.Infant; 
    } 
    canSignContracts(): boolean { return false; } 
} 
 
class Child extends Person  { 
    constructor(dateOfBirth: Date) { 
        super(dateOfBirth); 
        this.Category = PersonCategory.Child; 
    } 
    canSignContracts(): boolean { return false; } 
} 
 
class Adult extends Person  { 
    constructor(dateOfBirth: Date) { 
        super(dateOfBirth); 
        this.Category = PersonCategory.Adult; 
    } 
    canSignContracts(): boolean { return true; } 
} 

Each of these classes uses inheritance to extend the Person class. As the DateOfBirth property has been declared as private, and is ...