Builder pattern

Author: blue32a

README.md

@@ -5,3 +5,4 @@
 ### Creational
 
 - [Abstract Factory](./src/AbstractFactory/README.md)
+- [Builder](./src/Builder/README.md)

src/AbstractFactory/index.ts

@@ -1,3 +1,5 @@
+export {};
+
 interface AbstractFactory {
   createProductA(): AbstractProductA;
   createProductB(): AbstractProductB;

src/Builder/README.md

@@ -0,0 +1,43 @@
+## Builder
+
+https://refactoring.guru/ja/design-patterns/builder
+
+```mermaid
+classDiagram
+  class Client
+
+  class Director {
+    builder
+    construct()
+  }
+
+  class Builder {
+    <<Interface>>
+    buildPart1()
+    buildPart2()
+    buildPart3()
+  }
+
+  class ConcreteBuilder1 {
+    buildPart1()
+    buildPart2()
+    buildPart3()
+    getResult()
+  }
+
+  class ConcreteBuilder2 {
+    buildPart1()
+    buildPart2()
+    buildPart3()
+    getResult()
+  }
+
+  ConcreteBuilder1 ..|> Builder
+  ConcreteBuilder2 ..|> Builder
+
+  Director ..> Builder
+
+  Client ..> Director: use
+  Client ..> ConcreteBuilder1: use
+  Client ..> ConcreteBuilder2: use
+```

src/Builder/index.ts

@@ -0,0 +1,83 @@
+export {};
+
+interface Builder {
+  producePartA(): void;
+  producePartB(): void;
+  producePartC(): void;
+}
+
+class ConcreteBuilder1 implements Builder {
+  private product: Product1;
+
+  constructor() {
+    this.product = new Product1();
+  }
+
+  public reset(): void {
+    this.product = new Product1();
+  }
+
+  public producePartA(): void {
+    this.product.parts.push('PartA1');
+  }
+
+  public producePartB(): void {
+    this.product.parts.push('PartB1');
+  }
+
+  public producePartC(): void {
+    this.product.parts.push('PartC1');
+  }
+
+  public getProduct(): Product1 {
+    const result = this.product;
+    this.reset();
+    return result;
+  }
+}
+
+class Product1 {
+  public parts: string[] = [];
+
+  public listParts(): void {
+    console.log(`Product parts: ${this.parts.join(', ')}\n`);
+  }
+}
+
+class Director {
+  private builder: Builder;
+
+  constructor(builder: Builder) {
+    this.builder = builder;
+  }
+
+  public buildMinimalViableProduct(): void {
+    this.builder.producePartA();
+  }
+
+  public buildFullFeaturedProduct(): void {
+    this.builder.producePartA();
+    this.builder.producePartB();
+    this.builder.producePartC();
+  }
+}
+
+function clientCode() {
+  const builder = new ConcreteBuilder1();
+  const director = new Director(builder);
+
+  console.log('Standard basic product:');
+  director.buildMinimalViableProduct();
+  builder.getProduct().listParts();
+
+  console.log('Standard full featured product:');
+  director.buildFullFeaturedProduct();
+  builder.getProduct().listParts();
+
+  console.log('Custom product:');
+  builder.producePartA();
+  builder.producePartC();
+  builder.getProduct().listParts();
+}
+
+clientCode();