I’ve been thinking about this question for a bit and after a bit of consideration I agree that implementing IEquatable<T> and IComparable<T> should only be done on sealed types. I went back and forth for a bit but then I thought of the following test. Under what circumstances should the following ever return false? IMHO, … Read more
I’d say it was just a mistake. I know many people (including myself) who believe that classes should indeed be sealed by default. There are at least a couple of people in the C# design team in that camp. The pendulum has swung somewhat away from inheritance since C# was first designed. (It has its … Read more
This is actually in my opinion an appropriate use case for 2.10 macros: you want access to information that you know the compiler has, but isn’t exposing, and macros give you a (reasonably) easy way to peek inside. See my answer here for a related (but now slightly out-of-date) example, or just use something like … Read more
Well, you are testing with only two levels of inheritance, and you are not getting to the point that you’re “further overriding” a method. If you make it three, you can see what sealed does: class Base { public virtual void Test() { … } } class Subclass1 : Base { public sealed override void … Read more
No, at the time of this writing there is not. There is a proposal for such a keyword which is still being considered, but may or may not ever be implemented. See: github.com/Microsoft/TypeScript/issues/9264, and github.com/Microsoft/TypeScript/issues/8306
A class which is extensible implements the feature that it can be extended — that’s a feature like any other feature of the class, and should be treated like one, no different from a method. All features should be thought through carefully to ensure that they meet the goals of the customer using the feature. … Read more
C++11 solution In C++11, you can seal a class by using final keyword in the definition as: class A final //note final keyword is used after the class name { //… }; class B : public A //error – because class A is marked final (sealed). { // so A cannot be derived from. //… … Read more
It is a class that: internal: Can only be accessed from within the assembly it is defined (or friend assemblies). sealed: Cannot be inherited. Marking classes as internal is a way of preventing outside users of an assembly from using them. It’s really a form of design encapsulation and IMHO it is good practice to … Read more
The difference is that all subclasses of a sealed class (whether it’s abstract or not) must be in the same file as the sealed class.
This may help you: +————–+—+————————-+——————+———————+ | Class Type | | Can inherit from others | Can be inherited | Can be instantiated | |————–|—|————————-+——————+———————+ | normal | : | YES | YES | YES | | abstract | : | YES | YES | NO | | sealed | : | YES | NO | … Read more