Java – is there a “subclassof” like instanceof?
instanceof can handle that just fine.
subclass
How to create an immutable dictionary in python?
It is possible to create immutable dict using just standard library. from types import MappingProxyType power_levels = MappingProxyType( { “Kevin”: 9001, “Benny”: 8000, } ) See source of idea with more detailed explanation
Java: returning subclass in superclass method signature
This is a good question and a real problem. The easiest way to deal with it in Java likely involves the use of generics, as mentioned in Jochen’s answer. There’s a good discussion of the issue and a reasonable solution in this blog entry on Using Inheritance with Fluent Interfaces, which combines generics with the … Read more
In C# 4.0, is it possible to derive a class from a generic type parameter?
Generic types in C# are not C++ templates; remember, a generic type must work for all possible type arguments. A template need only work for the constructions you actually make. This question is a duplicate; see my answer to Why cannot C# generics derive from one of the generic type parameters like they can in … Read more
Subclassing dict: should dict.__init__() be called?
You should probably call dict.__init__(self) when subclassing; in fact, you don’t know what’s happening precisely in dict (since it’s a builtin), and that might vary across versions and implementations. Not calling it may result in improper behaviour, since you can’t know where dict is holding its internal data structures. By the way, you didn’t tell … Read more
Expose a private Objective-C method or property to subclasses
One way to solve this is to re-declare the property in your subclass’s class extension, and then add an @dynamic statement so that the compiler won’t create an overriding implementation of that property. So something like: @interface SuperClass () @property (nonatomic, strong) id someProperty; @end …. @interface SubClass () @property (nonatomic, strong) id someProperty; @end … Read more
Why shouldn’t I subclass a UIButton?
The Cocoa frameworks take the approach that the Object Composition pattern is more appropriate than traditional class hierarchy. In general, this means that there is likely to be a property on UIButton where you can set another object to handle various aspects of the button. This is the preferred way to “customize” how your button … Read more
Disallow subclasses from overriding Java method
You can declare the method to be final, as in: public final String getId() { … } For more info, see http://docs.oracle.com/javase/tutorial/java/IandI/final.html