What does the colon mean?

Question

I have a class header:

public class Person : Human

What does the : mean?

Is it something like the extends in Java? And what do I need it for?

While it has been already answered I believe that it's a so basic question and you shouldn't come to StackOverflow to ask something you can check on MSDN... — Matías Fidemraizer, May 14 '16 at 13:08

score 6 · Accepted Answer · answered May 14 '16 at 12:42

6

The ":" means "extends" if you're comparing it to java. Every class extends object by default. You need it to extend a class, I'm assuming you already know what extending is, if not feel free to ask.

answered May 14 '16 at 12:42

mrousavy

311
1
8

6

It can also mean "implements", for interfaces. – parachutingturtle May 14 '16 at 13:02

score 1 · Answer 2 · edited May 23 '17 at 12:18

In this case, the colon operator is separating the class name "Person" from the base class "Human". The colon here implies inheritance, so you are right! Person inherits the fields/methods of Human. You can also add other methods to Person to provide it with additional functionality.

Here is a similar post with other functions available with the colon operator: In C# what category does the colon " : " fall into, and what does it really mean?

score 0 · Answer 3 · answered May 14 '16 at 12:46

The colon operator (:) is used to extend a class, like in c++. This means that a Person is a specific kind of Human. It can participate in any context that relates to a Human (such as being passed as a method argument), but may have specific behaviors (i.e., it may override some of Human's method, or add new ones).

score 0 · Answer 4 · answered May 14 '16 at 12:52

The ':' operator is used for inheriting from a super class(Synonymous to the 'extends' keyword in Java).

Why is inheritance needed - It's a really powerful concept for modelling the relations in the world around us. Technically, the subclasses tend to be more specific and the superclasses are more generalized. For example - Consider Student : Person. Here the Student is the subclass and the Person is the super class.

class Person
{
  public string name;
}

class Student : Person
{
  public string id;
}

This translates to the fact that Every Student is also a Person and a student will inherently have 'name' as an attribute. But every Person needn't be a student and won't have 'id' implicitly.

What does the colon mean?

4 Answers4