Comprehensive guide to design patterns in D programming, including UML diagrams, pattern summaries, and implementation tips for expert software engineers.
Welcome to the Design Pattern Reference Cheat Sheet, a comprehensive guide tailored for expert software engineers and architects working with the D programming language. This section provides a quick reference to various design patterns, complete with UML diagrams, pattern summaries, and implementation tips. Our goal is to help you leverage these patterns effectively in your systems programming projects.
UML (Unified Modeling Language) diagrams are essential tools for visualizing the structure and behavior of design patterns. In this section, we will use Hugo-compatible Mermaid.js diagrams to illustrate each pattern.
Each design pattern is summarized with its intent, key participants, and applicability. This will help you quickly understand the purpose and use cases of each pattern.
For each pattern, we provide key implementation tips, including considerations specific to the D programming language. This includes code snippets and best practices to ensure efficient and effective use of patterns in your projects.
1class Singleton {
2 private static Singleton instance;
3
4 private this() {
5 // Private constructor to prevent instantiation
6 }
7
8 static Singleton getInstance() {
9 if (instance is null) {
10 instance = new Singleton();
11 }
12 return instance;
13 }
14}
synchronized blocks or other concurrency mechanisms. 1interface Product {
2 void use();
3}
4
5class ConcreteProductA : Product {
6 void use() { writeln("Using Product A"); }
7}
8
9class ConcreteProductB : Product {
10 void use() { writeln("Using Product B"); }
11}
12
13abstract class Creator {
14 abstract Product factoryMethod();
15}
16
17class ConcreteCreatorA : Creator {
18 Product factoryMethod() { return new ConcreteProductA(); }
19}
20
21class ConcreteCreatorB : Creator {
22 Product factoryMethod() { return new ConcreteProductB(); }
23}
1interface GUIFactory {
2 Button createButton();
3 Checkbox createCheckbox();
4}
5
6class WinFactory : GUIFactory {
7 Button createButton() { return new WinButton(); }
8 Checkbox createCheckbox() { return new WinCheckbox(); }
9}
10
11class MacFactory : GUIFactory {
12 Button createButton() { return new MacButton(); }
13 Checkbox createCheckbox() { return new MacCheckbox(); }
14}
1class Product {
2 string partA;
3 string partB;
4}
5
6interface Builder {
7 void buildPartA();
8 void buildPartB();
9 Product getResult();
10}
11
12class ConcreteBuilder : Builder {
13 private Product product = new Product();
14
15 void buildPartA() { product.partA = "Part A"; }
16 void buildPartB() { product.partB = "Part B"; }
17 Product getResult() { return product; }
18}
19
20class Director {
21 void construct(Builder builder) {
22 builder.buildPartA();
23 builder.buildPartB();
24 }
25}
1interface Prototype {
2 Prototype clone();
3}
4
5class ConcretePrototype : Prototype {
6 int field;
7
8 this(int field) {
9 this.field = field;
10 }
11
12 Prototype clone() {
13 return new ConcretePrototype(this.field);
14 }
15}
dup method for array copying. 1class ObjectPool {
2 private Reusable[] pool;
3 private bool[] inUse;
4
5 this(int size) {
6 pool = new Reusable[size];
7 inUse = new bool[size];
8 for (int i = 0; i < size; i++) {
9 pool[i] = new Reusable();
10 }
11 }
12
13 Reusable acquire() {
14 for (int i = 0; i < pool.length; i++) {
15 if (!inUse[i]) {
16 inUse[i] = true;
17 return pool[i];
18 }
19 }
20 return null; // or throw an exception
21 }
22
23 void release(Reusable obj) {
24 for (int i = 0; i < pool.length; i++) {
25 if (pool[i] == obj) {
26 inUse[i] = false;
27 break;
28 }
29 }
30 }
31}
1interface Target {
2 void request();
3}
4
5class Adaptee {
6 void specificRequest() {
7 writeln("Specific request");
8 }
9}
10
11class Adapter : Target {
12 private Adaptee adaptee;
13
14 this(Adaptee adaptee) {
15 this.adaptee = adaptee;
16 }
17
18 void request() {
19 adaptee.specificRequest();
20 }
21}
1interface Implementor {
2 void operationImpl();
3}
4
5class ConcreteImplementorA : Implementor {
6 void operationImpl() {
7 writeln("ConcreteImplementorA operation");
8 }
9}
10
11class ConcreteImplementorB : Implementor {
12 void operationImpl() {
13 writeln("ConcreteImplementorB operation");
14 }
15}
16
17class Abstraction {
18 protected Implementor implementor;
19
20 this(Implementor implementor) {
21 this.implementor = implementor;
22 }
23
24 void operation() {
25 implementor.operationImpl();
26 }
27}
1interface Component {
2 void operation();
3}
4
5class Leaf : Component {
6 void operation() {
7 writeln("Leaf operation");
8 }
9}
10
11class Composite : Component {
12 private Component[] children;
13
14 void add(Component component) {
15 children ~= component;
16 }
17
18 void operation() {
19 foreach (child; children) {
20 child.operation();
21 }
22 }
23}
1interface Component {
2 void operation();
3}
4
5class ConcreteComponent : Component {
6 void operation() {
7 writeln("ConcreteComponent operation");
8 }
9}
10
11class Decorator : Component {
12 protected Component component;
13
14 this(Component component) {
15 this.component = component;
16 }
17
18 void operation() {
19 component.operation();
20 }
21}
22
23class ConcreteDecorator : Decorator {
24 this(Component component) {
25 super(component);
26 }
27
28 void operation() {
29 super.operation();
30 writeln("ConcreteDecorator operation");
31 }
32}
1interface Strategy {
2 void execute();
3}
4
5class ConcreteStrategyA : Strategy {
6 void execute() {
7 writeln("Executing strategy A");
8 }
9}
10
11class ConcreteStrategyB : Strategy {
12 void execute() {
13 writeln("Executing strategy B");
14 }
15}
16
17class Context {
18 private Strategy strategy;
19
20 this(Strategy strategy) {
21 this.strategy = strategy;
22 }
23
24 void executeStrategy() {
25 strategy.execute();
26 }
27}
1interface Observer {
2 void update();
3}
4
5class ConcreteObserver : Observer {
6 void update() {
7 writeln("Observer updated");
8 }
9}
10
11class Subject {
12 private Observer[] observers;
13
14 void attach(Observer observer) {
15 observers ~= observer;
16 }
17
18 void notify() {
19 foreach (observer; observers) {
20 observer.update();
21 }
22 }
23}
classDiagram
class Singleton {
- Singleton instance
- Singleton()
+ getInstance() Singleton
}
Description: This diagram illustrates the Singleton pattern, showing the private instance and the public method to access it.
classDiagram
class Creator {
<<abstract>>
+ factoryMethod() Product
}
class ConcreteCreatorA {
+ factoryMethod() Product
}
class ConcreteCreatorB {
+ factoryMethod() Product
}
class Product {
<<interface>>
}
class ConcreteProductA {
}
class ConcreteProductB {
}
Creator <|-- ConcreteCreatorA
Creator <|-- ConcreteCreatorB
Product <|.. ConcreteProductA
Product <|.. ConcreteProductB
ConcreteCreatorA --> ConcreteProductA
ConcreteCreatorB --> ConcreteProductB
Description: This diagram shows the Factory Method pattern, highlighting the relationship between creators and products.
classDiagram
class Target {
<<interface>>
+ request()
}
class Adapter {
+ request()
}
class Adaptee {
+ specificRequest()
}
Target <|.. Adapter
Adapter --> Adaptee
Description: This diagram represents the Adapter pattern, showing how the Adapter class implements the Target interface and uses the Adaptee.
Experiment with the provided code examples by modifying them to suit different scenarios. For instance, try creating a new ConcreteProduct in the Factory Method pattern or adding a new operation in the Decorator pattern. This hands-on approach will deepen your understanding of each pattern’s flexibility and applicability.
Remember, this is just the beginning. As you progress, you’ll build more complex and interactive systems using these patterns. Keep experimenting, stay curious, and enjoy the journey!