Part 12 - Namespaces

A name that uniquely identifies a set of objects so there is no ambiguity when objects from different sources are used together.

Namespaces are useful because if you have, for example, a Dog namespace and a Furniture namespace, and they both have a Leg class, you can refer to Dog.Leg and Furniture.Leg and be clear about which class you are mentioning.

Declaring a Namespace

To declare a namespace, all that is required is that you put namespace followed by a name at the top of your file.

namespace Tutorial

class Thing():
    pass

This creates your class Tutorial.Thing. While coding inside your namespace, it will be transparently Thing.

To declare a namespace within a namespace, just place a dot . inbetween each other.

Declare a namespace at the top of all your files.
Use PascalCase for all your namespaces.

Importing Another Namespace

To use classes from another namespace, you would use the import keyword.
The most common namespace you will import is System.

import System

Console.WriteLine()

System.Console.WriteLine()

Both produce the exact same code, it's just easier and clearer with the import.

Don't be afraid to import, just don't import namespaces that you aren't using.

When importing, import included namespaces first, such as System or Boo.Lang.
Then import your 3rd party namespaces.
Alphabetize the two groups seperately.

If you are importing from another assembly, you would use the phrase import <target> from <assembly>, for example

import System.Data from System.Data
import Gtk from "gtk-sharp"

System.Data is part of an external library which can be added, System.Data.dll. Gtk is part of the Gtk# library, which, since it has a special name (with a dash in it), it must be quoted.

Only use the import <target> from <assembly> if you are using one file and one file only. If you are using more than that, you should be using a build tool, such as NAnt, which is discussed in Part 19 - Using the Boo Compiler.

Exercises

  1. Figure out a good exercise for this section.

Go on to Part 13 - Enumerations