Unfortunately no, covariant return types aren’t supported in C# for method overriding. (Ditto contravariant parameter types.) If you’re implementing an interface you can implement it explicitly with the “weak” version and also provide a public version with the stronger contract. For simple overriding of a parent class, you don’t have this luxury I’m afraid 🙁 … Read more
I believe that the more you start to develop using design patterns, you’ll find more and more often where composition is going to be favored over inheritance. I actually believe in the Head First: Design Patterns book that “Favor Composition Over Inheritance” is one of the primary design principles. Your example of being able to … Read more
It’s a reported bug – you can vote for it here: https://youtrack.jetbrains.com/issue/PY-16132
Thoughts: Avoid extending JFrame as it ties your GUI to being, well a JFrame. If instead you concentrate on creating JPanels instead, then you have the freedom to use these JPanels anywhere needed — in a JFrame, or JDialog, or JApplet, or inside of another JPanel, or swapped with other JPanels via a CardLayout. Avoid … Read more
No, is only works for checking the type of an object, not for a given Type. You want Type.IsAssignableFrom: if (attr != null && typeof(IInterface).IsAssignableFrom(type)) Note the order here. I find that I almost always use typeof(…) as the target of the call. Basically for it to return true, the target has to be the … Read more
As said, JavaScript is a dynamic typed language based on prototypal inheritance, so you can’t really use the same approach of typed languages. A JS version of what you wrote, could be: function Shape(){ throw new Error(“Abstract class”) } Shape.prototype.printSurface = function () { throw new Error (“Not implemented”); } function Rect() { // constructor; … Read more
Here’s an example of why it doesn’t make sense to be able to override the visibility: interface someI { void doYourWork(); } public class A : someI { public void doYourWork() { //… } } public class B : someI { private void doYourWork() { //… } } void Main() { List<someI> workers = getWorkers(); … Read more
A simple hack I have used is: class SuperFoo(models.Model): name = models.CharField(‘name of SuperFoo instance’, max_length=50) … class Meta: abstract = True class Foo(SuperFoo): … # do something that changes verbose_name of name field of SuperFoo Foo._meta.get_field(‘name’).verbose_name=”Whatever”
Suppose you create a View class that displays your items in a certain way. Now you decide you also want a version of it which is scrollable, so you create a ScrollableView which inherits the View. Later you decide you also want a version with a border so you now need to make a BorderedView … Read more
Really you’re asking a lot of different questions here, so I’m going to do my best to answer each one in turn. First you want to know how data members are aligned. Member alignment is compiler defined, but because of how CPUs deal with misaligned data, they all tend to follow the same guideline that … Read more