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What is the purpose of an Objective C category?
Categories provide the ability to add functionality to an object without subclassing or changing the actual object. A handy tool, they are often used to add methods to existing classes, such as NSString or your own custom objects.
What are categories used for Objective C?
You use categories to define additional methods of an existing class—even one whose source code is unavailable to you—without subclassing. You typically use a category to add methods to an existing class, such as one defined in the Cocoa frameworks.
Can an object extend a trait Scala?
Unlike a class, Scala traits cannot be instantiated and have no arguments or parameters. However, you can inherit (extend) them using classes and objects.
Is Objective-C and C the same?
The main difference in C and Objective C is that C is a procedure programming language which doesn’t support the concepts of objects and classes and Objective C is Object-oriented language which contains the concept of both procedural and object-oriented programming languages.
Why do we need traits in Scala [ Stack Overflow ]?
If the idea was to enforce that you can inherit from multiple traits but only a single class, it seems awfully easy to get around.
Why do we need package objects in Scala?
Objects can’t. Package Objects are a way to overcome some of the limitations of packages, if we didn’t have packages, we wouldn’t need package objects. Type Erasure. It is perfectly possible to keep generic types around when compiling to the JVM, e.g. you could store them in annotations.
Why do we have to have null in Scala?
It is just not possible to automatically map between null and Option in any sane way, when interoperating with real-world Java code. You have to have null in Scala, even though we rather wished it weren’t there. The problem with having constructors and state in a trait (which then makes it a class) is with multiple inheritance.