You want: (Achievable with virtual inheritance) A / \ B C \ / D And not: (What happens without virtual inheritance) A A | | B C \ / D Virtual inheritance means that there will be only 1 instance of the base A class not 2. Your type D would have 2 vtable pointers … Read more
The short answer is: because the language designers decided not to. Basically, it seemed that both the .NET and Java designers did not allow multiple inheritance because they reasoned that adding MI added too much complexity to the languages while providing too little benefit. For a more fun and in-depth read, there are some articles … Read more
The most obvious problem is with function overriding. Let’s say have two classes A and B, both of which define a method doSomething. Now you define a third class C, which inherits from both A and B, but you don’t override the doSomething method. When the compiler seed this code… C c = new C(); … Read more
Multiple inheritance can be achieved in ECMAScript 6 by using Proxy objects. Implementation function getDesc (obj, prop) { var desc = Object.getOwnPropertyDescriptor(obj, prop); return desc || (obj=Object.getPrototypeOf(obj) ? getDesc(obj, prop) : void 0); } function multiInherit (…protos) { return Object.create(new Proxy(Object.create(null), { has: (target, prop) => protos.some(obj => prop in obj), get (target, prop, receiver) … Read more
Yes, you can do it. An interface can extend multiple interfaces, as shown here: interface Maininterface extends inter1, inter2, inter3 { // methods } A single class can also implement multiple interfaces. What if two interfaces have a method defining the same name and signature? There is a tricky point: interface A { void test(); … Read more
Mixins may contain state, (traditional) traits don’t. Mixins use “implicit conflict resolution”, traits use “explicit conflict resolution” Mixins depends on linearization, traits are flattened. Lecture about traits ad 1. In mixins you can define instance variables. Traits do not allow this. The state must be provided by the composing class (=class using the traits) ad … Read more
You could create interfaces for animal classes (class in the biological meaning), such as public interface Equidae for horses and public interface Avialae for birds (I’m no biologist, so the terms may be wrong). Then you can still create a public class Bird implements Avialae { } and public class Horse implements Equidae {} and … Read more
Consider encapsulation: public class TwoTypesConsumer { private TomatoConsumer tomatoConsumer = new TomatoConsumer(); private AppleConsumer appleConsumer = new AppleConsumer(); public void consume(Tomato t) { tomatoConsumer.consume(t); } public void consume(Apple a) { appleConsumer.consume(a); } public static class TomatoConsumer implements Consumer<Tomato> { public void consume(Tomato t) { ….. } } public static class AppleConsumer implements Consumer<Apple> { public … Read more
Multiple inheritance (abbreviated as MI) smells, which means that usually, it was done for bad reasons, and it will blow back in the face of the maintainer. Summary Consider composition of features, instead of inheritance Be wary of the Diamond of Dread Consider inheritance of multiple interfaces instead of objects Sometimes, Multiple Inheritance is the … Read more
Consider just using composition instead of trying to simulate Multiple Inheritance. You can use Interfaces to define what classes make up the composition, eg: ISteerable implies a property of type SteeringWheel, IBrakable implies a property of type BrakePedal, etc. Once you’ve done that, you could use the Extension Methods feature added to C# 3.0 to … Read more