The Kitty application

The kitty.rb file is a simple, small ruby program that demonstrates most of Caty’s functionality. You can download it and play with it! Or you read on and see how it was created.

How it works

Now, what exactly does our kitty do? As every kitty, it loves to just lay in the sun, doze and sleep, sleep and doze. Now and then it has to eat a bit, sometimes fish, sometimes a mouse. During all of this, the kitty likes to meow a bit and purr a while.

skeleton

First, let’s lay out the skeleton of the application:

require 'rubygems'
require 'caty'

class Kitty < Caty
end

Kitty.start!

That’s it already. Now we only have to populate the Kitty class and we’re set.

eating

A picture of a cat playing with a computer mouse

So, let’s get our kitten eat something. In order to accomplish that, we add an instance method to the class, like so:

def eat
    puts "The kitty eats fish!"
end

Now we can feed the kitty:

$> kitty.rb eat
The kitty eats fish!

But the kitty soon becomes fed up with fish and demands something else. So let’s make this more variable and have the user supply what the kitty eats:

def eat( something )
   puts "The kitty eats #{something}!"
end

Here the kitty gets some catfood:

$> kitty.rb eat catfood
The kitty eats catfood!

That’s better! But our little cat is still very hungry, so we add a switch with which we can determine how much the kitty should eat.

task_options :amount => 1

def eat( something )
   puts "The kitty eats #{task_options.amount} #{something}!"
end

This let’s us do the following:

$> kitty.rb eat mouse
The kitty eats 1 mouse!
$> kitty.rb eat mice -amount=3
The kitty eats 3 mice!

sleeping

A picture of a sleeping kitten

With such a full belly, the kitty now needs to sleep. It strolls into a sunlit corner and curls itself up into a small hairball:

def sleep
    puts 'The kitty sleeps...'
end

$> kitty.rb sleep
The kitty sleeps...

But sometimes the kitty not so much sleeps, but rather just dozes. Although the two are actually the same. So let’s add an alias for sleep:

map :doze => :sleep

$> kitty.rb doze
The kitty sleeps...

meow and purr

A picture of a yawning lion

The little kitten has slept enough and it’s in a playful mood now. It meows at you a lot:

def meow
    puts 'meow!'
end

$> kitty.rb meow
meow!

In fact, if you do nothing but look at it, it meows:

default :meow

$> kitty.rb
meow!

and even when you feed it and when it’s dreaming – it meows!

before do
    puts 'meow!'
end

$> kitty.rb eat grass
meow!
The kitty eats 1 grass!
$> kitty.rb sleep
meow!
The kitty sleeps...

We’d better stroke it a bit, to calm it down. We best do this everytime we do something with it:

after do
    puts 'purrr...'
end

$> kitty.rb eat grass
meow!
The kitty eats 1 grass!
purrr...
$> kitty.rb sleep
meow!
The kitty sleeps...
purrr...

quiet

Now we’re gonna teach our kitty something: to be quiet!

global_options do
    boolean :quiet => false
end

That should calm it down:

before do
    puts 'meow!' unless global_options.quiet
end

$> kitty.rb eat berry --quiet
The kitty eats 1 berry!
purrr...

Fairy action!

A stone fairy statue

Then a fairy comes flying by and gives us three wishes. We wish for a pack of sweets, a rainbow dress (like the one lepachauns wear, you know) and that our kitty be ablo to speak. We get everything pronto:

help_task

# ...

desc('No meowing.')
boolean :quiet, false

# ...

desc('SOMETHING', cut("
    Eats SOMETHING.
    You can give the kitty any -amount of food.
"))
def eat( something )

# ...

desc("Sleeps a bit.")
def sleep

# ...

desc('meow?')
def meow

# ...

Bewildered we turn to our kitten, which looks at us with smiling eyes, and ask it:

$> kitty.rb help
Commands
========

eat SOMETHING [-amount=1]  # Eats SOMETHING.
meow                       # meow?
help [TOKEN]               # Provides help about the program.
sleep                      # Sleeps a bit.

Global Options
==============

--quiet=false              # No meowing.

we emit a cry of joy! It worked. Gladly we offer the fairy some of our sweets and ask the kitty:

$> kitty.rb help eat
eat SOMETHING [-amount=1]

Eats SOMETHING.
You can give the kitty any -amount of food.

Great! Let’s ask another question!

$> kitty.rb help sleep
sleep

Sleeps a bit.

Aliases: doze

How wise the kitty is!

separating

Now, the kitten has grown older and so have we and it is time to move from childhood to adultery… ah… I mean adulthood. And that means that the time of playing and eating all at the same place is over. A serios cat has to learn to separate work and fun and so we put sleeping in a different location:

## sleepy.rb
Kitty.append do

    desc("Sleeps a bit.")
    map :doze => :sleep

    def sleep
        puts 'The kitty sleeps...'
    end

end

## kitty.rb
# ...

class Kitty < Caty
    # ...
end

require 'sleepy.rb'

That’s it!

If you followed the above story, you should now know most of Caty’s features. Now grab the kitty’s source and start experimenting!

Images used on this page

All those were taken from http://www.morguefile.com and are licensed under the morgueFile Free License.