Interfaces and Inheritance

lesson#19.1 - Interfaces and Inheritance/inheritance.d

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+module inheritance; 
+
+// ****** interfaces ******
+// 1) its member functions are abstract (have no implementation)
+// 2) interfaces can inherit only form other interfaces
+// 3) inheritance syntax => interface/class Name: Inherit_Name {}
+
+interface IAnimal {
+	void makeSound(); 	// abstract function ('abstract' keyword could be used in a class to achieve the same functionality)
+	// ...
+
+	//static/final type name() { ... } 	// static and final members do have an implementation, are inherited, and cannot be overriden
+}
+
+// ****** inheritance ******
+// 1) interfaces can inherit only from other interfaces
+// 2) classes can inherit from multiple interfaces
+// 3) interface members must be implemented, unless they are static or final
+
+class Cat: IAnimal { 	// Cat inherits from IAnimal interface
+	this() { }
+
+	void makeSound() { 	// implements makeSound function
+		import std.stdio: writeln;
+
+		writeln("Meow...");
+	}
+}
+
+//--------------------------//
+
+class Dog: IAnimal { 	// Dog inherits from IAnimal interface
+	this() { }
+
+	void makeSound() { 	// implements makeSound function
+		import std.stdio: writeln;
+
+		writeln("Woof woof...");
+	}
+}
+
+class Cow: IAnimal { 	// Cow inherits from IAnimal interface
+	this() { }
+
+	void makeSound() { 	// implements makeSound function
+		import std.stdio: writeln;
+
+		writeln("Moooo...");
+	}
+}
+
+
+
+
+
+
+
+

lesson#19.1 - Interfaces and Inheritance/main.d

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+import inheritance;
+
+void animalMakeSound(IAnimal animal) {
+	animal.makeSound();
+}
+
+void main() {
+	Cat cat = new Cat();	// Cat class
+	cat.makeSound();		// calling makeSound function
+
+	// we can use IAnimal interface to call its makeSound function
+	// given the class object that inherits from that interface
+	animalMakeSound(new Cat());
+	animalMakeSound(new Dog());
+	animalMakeSound(new Cow());
+}
+
+
+
+