Type-safe and generic implementation of the build pattern in Typescript

How to use it

$3

* Conditions:
* No methods in class
* No need to keep properties private and controlling object manipulation

``ts
// Usage of the Builder
const person: Person = new Builder(Person)
.with({ firstname: 'Magne' })
.with({ surname: 'Thor' })
.with({ birthday: new Date('2000-01-11') })
.build();


// Optional implementation of the Validatable interface. Builder calls validate() BEFORE an object is build.
class Person implements Validatable {
public readonly title?: string;
public readonly firstname: string;
public readonly surname: string;
public readonly birthday?: Date;

constructor(builder: Builder & Person) {
this.title = builder.title;
this.firstname = builder.firstname;
this.surname = builder.surname;
this.birthday = builder.birthday;
}

validate(): boolean {
// Do your validation here
return true;
}
}
`

$3

* Use cases:
* Model is implemented in domain driven fassion, that is class contains methods which are encapsulating business logic
* Property access is kept private to enforce object manipulation through business logic methods


`ts
// Usage of the DomainBuilder
const correctVo: PersonVo = new DomainBuilder(PersonVo)
.with({ firstname: 'Magne' })
.with({ surname: 'Thor' })
.with({ birthday: new Date('2000-01-11') })
.build();

// Model definition
interface PersonProps extends Validatable {
readonly title?: string;
readonly firstname: string;
readonly surname: string;
readonly birthday?: Date;
}

export class PersonVo implements PersonProps {
private _title?: string;
private _firstname: string;
private _surname: string;
private _birthday?: Date;

constructor(builder: DomainBuilder & PersonProps) {
this._title = builder.title;
this._firstname = builder.firstname;
this._surname = builder.surname;
this._birthday = builder.birthday;
}

get title(): string | undefined {
return this._title;
}
get firstname(): string {
return this._firstname;
}
get surname(): string {
return this._surname;
}
get birthday(): Date | undefined {
return this._birthday;
}

validate(): boolean {
// Do your validation here
return true;
}

public changeSurname(newName: string): void {
this._surname = newName;
}
}
``

Implementation of Validatable interface

Implement the Validatable interface if you want to run validations before the builder creates the object.