Abstract Factory em TypeScript
O Abstract Factory é um padrão de projeto criacional, que resolve o problema de criar famílias inteiras de produtos sem especificar suas classes concretas.
O Abstract Factory define uma interface para criar todos os produtos distintos, mas deixa a criação real do produto para classes fábrica concretas. Cada tipo de fábrica corresponde a uma determinada variedade de produtos.
O código cliente chama os métodos de criação de um objeto fábrica em vez de criar produtos diretamente com uma chamada de construtor (usando operador new). Como uma fábrica corresponde a uma única variante de produto, todos os seus produtos serão compatíveis.
O código cliente trabalha com fábricas e produtos somente através de suas interfaces abstratas. Ele permite que o mesmo código cliente funcione com produtos diferentes. Você apenas cria uma nova classe fábrica concreta e a passa para o código cliente.
Se você não conseguir descobrir a diferença entre os padrões Factory, Factory Method e Abstract Factory, leia nossa Comparação Factory.
Complexidade:
Popularidade:
Exemplos de uso: O padrão Abstract Factory é bastante comum no código TypeScript. Muitas frameworks e bibliotecas o utilizam para fornecer uma maneira de estender e personalizar seus componentes padrão.
Identificação: O padrão é fácil de reconhecer pelos seus métodos, que retornam um objeto fárica. Em seguida, a fábrica é usado para criar subcomponentes específicos.
Exemplo conceitual
Este exemplo ilustra a estrutura do padrão de projeto Abstract Factory. Ele se concentra em responder a estas perguntas:
- De quais classes ele consiste?
- Quais papéis essas classes desempenham?
- De que maneira os elementos do padrão estão relacionados?
index.ts: Exemplo conceitual
/**
* The Abstract Factory interface declares a set of methods that return
* different abstract products. These products are called a family and are
* related by a high-level theme or concept. Products of one family are usually
* able to collaborate among themselves. A family of products may have several
* variants, but the products of one variant are incompatible with products of
* another.
*/
interface AbstractFactory {
createProductA(): AbstractProductA;
createProductB(): AbstractProductB;
}
/**
* Concrete Factories produce a family of products that belong to a single
* variant. The factory guarantees that resulting products are compatible. Note
* that signatures of the Concrete Factory's methods return an abstract product,
* while inside the method a concrete product is instantiated.
*/
class ConcreteFactory1 implements AbstractFactory {
public createProductA(): AbstractProductA {
return new ConcreteProductA1();
}
public createProductB(): AbstractProductB {
return new ConcreteProductB1();
}
}
/**
* Each Concrete Factory has a corresponding product variant.
*/
class ConcreteFactory2 implements AbstractFactory {
public createProductA(): AbstractProductA {
return new ConcreteProductA2();
}
public createProductB(): AbstractProductB {
return new ConcreteProductB2();
}
}
/**
* Each distinct product of a product family should have a base interface. All
* variants of the product must implement this interface.
*/
interface AbstractProductA {
usefulFunctionA(): string;
}
/**
* These Concrete Products are created by corresponding Concrete Factories.
*/
class ConcreteProductA1 implements AbstractProductA {
public usefulFunctionA(): string {
return 'The result of the product A1.';
}
}
class ConcreteProductA2 implements AbstractProductA {
public usefulFunctionA(): string {
return 'The result of the product A2.';
}
}
/**
* Here's the the base interface of another product. All products can interact
* with each other, but proper interaction is possible only between products of
* the same concrete variant.
*/
interface AbstractProductB {
/**
* Product B is able to do its own thing...
*/
usefulFunctionB(): string;
/**
* ...but it also can collaborate with the ProductA.
*
* The Abstract Factory makes sure that all products it creates are of the
* same variant and thus, compatible.
*/
anotherUsefulFunctionB(collaborator: AbstractProductA): string;
}
/**
* These Concrete Products are created by corresponding Concrete Factories.
*/
class ConcreteProductB1 implements AbstractProductB {
public usefulFunctionB(): string {
return 'The result of the product B1.';
}
/**
* The variant, Product B1, is only able to work correctly with the variant,
* Product A1. Nevertheless, it accepts any instance of AbstractProductA as
* an argument.
*/
public anotherUsefulFunctionB(collaborator: AbstractProductA): string {
const result = collaborator.usefulFunctionA();
return `The result of the B1 collaborating with the (${result})`;
}
}
class ConcreteProductB2 implements AbstractProductB {
public usefulFunctionB(): string {
return 'The result of the product B2.';
}
/**
* The variant, Product B2, is only able to work correctly with the variant,
* Product A2. Nevertheless, it accepts any instance of AbstractProductA as
* an argument.
*/
public anotherUsefulFunctionB(collaborator: AbstractProductA): string {
const result = collaborator.usefulFunctionA();
return `The result of the B2 collaborating with the (${result})`;
}
}
/**
* The client code works with factories and products only through abstract
* types: AbstractFactory and AbstractProduct. This lets you pass any factory or
* product subclass to the client code without breaking it.
*/
function clientCode(factory: AbstractFactory) {
const productA = factory.createProductA();
const productB = factory.createProductB();
console.log(productB.usefulFunctionB());
console.log(productB.anotherUsefulFunctionB(productA));
}
/**
* The client code can work with any concrete factory class.
*/
console.log('Client: Testing client code with the first factory type...');
clientCode(new ConcreteFactory1());
console.log('');
console.log('Client: Testing the same client code with the second factory type...');
clientCode(new ConcreteFactory2());
Output.txt: Resultados da execução
Client: Testing client code with the first factory type...
The result of the product B1.
The result of the B1 collaborating with the (The result of the product A1.)
Client: Testing the same client code with the second factory type...
The result of the product B2.
The result of the B2 collaborating with the (The result of the product A2.)
