t5-ruby-classes

Before I even get in to when or how or why to use classes in Ruby, it makes sense to first cover what a class is. The way that I see it is that a class is in one sense a group of objects. All strings belong to the class 'Strings', all integers belong to the class 'Integers', and confusingly enough all classes belong to the class 'Class'. However, it's not that simple. Classes are not just containers of objects, like an array or a hash, but they are also a blueprint or a template for making new objects that belong to that class, so that you don't have to go back and create each new item piece by piece. I could ramble on and on, trying to make sense of all the technical vocabulary in terms of one another, but every time I try, it comes out in a mumbo-jumbo mess that isn't so clear. So, please indulge me while a paint a picture for you.

You are a supernatural being. You have just made a new world and are sitting in a field of lush grass taking in the view of your new creation. You like the look of the rolling hills, the feeling of the sun on your face and the wind in your hair. As a feeling of pride and accomplishment starts to lull you into a much deserved nap, your daughter comes up and taps you on the shoulder.

"Good job Daddy", she says. "But why's it so green? Don't you like colors?"

You sit up and take a look around, and think to yourself, 'shit, she's right'. As exhausted as you are, you know you're never going to get that nap until she sees some color, so you ask her how she thinks you should put some color into this new world. "Well, I like flowers", she says.

So you have a new task. You sit and think about it, and as easy as it would be to make one flower and then just copy it over and over to fill the landscape, you know that your daughter is going to want more than one flower and more than one color. The problem is that you're just so tired. The thought of creating flower after flower after flower makes your spine shudder.

Suddenly you have an idea. What if you had a blueprint for creating flowers? A template that once plugged in with a couple different modifiers could make individual flowers? A template (class) that could be used over and over to create these flowers (objects), which all share certain simliarities but each have their own characteristics? Good thing that you've been studying Ruby when you're not busy being a god. So you break out your creation computer and open up your trusty text editor. Enter classes:

So you have to build a template (a class) that represents the characteristics of a flower and contains the functions that a flower is going to experience in the course of its life. You know from your studies that you have define your class with the keyword class followed by the name of your class written in CamelCase:

class Flowers
end

You now have your template, but it is empty. You could go ahead and create a new flower but it wouldn't do anything. It has no functions (methods) and there is nothing that distinguishes what that flower is. You think about it and realize that all the objects you are going to create have a set of characteristics: 'number of petals' and 'petal color'. But those characteristics are going to change from flower to flower. Enter the initialize method. Think of this as a starter method. Each time you create an instance of your class, a new flower, this method will run and basically set up your new flower. You can define this method so that every time you create a new flower, you pass in these characteristics so that each flower you create has its own characteristics.


         class Flowers
          
               def initialize(petal_num, petal_color)
            
                @petal_num = petal_num
                @petal_color = petal_color
                puts "You made a flower with #{petal_num} #{petal_color} petals."
            
               end
          
         end

Now outside of the class you can pick a name for a flower and set it equal to Flowers.new(), and inside of the parenthesis put how many petals you want it to have and what color to make those petals:

new_flower = Flowers.new(5, "blue")
#=> "You made a flower with 5 blue petals."

You have created a new flower. That flower is an instance of the Flowers class. Now that you have started a template, you can create more flowers, more instances of the Flowers class with different numbers of petals of different colors.

Being a supernatural being you foresee your daughter complaining that the flower really doesn't do anything. Luckily, now that you have a class Flowers you can add functions (methods) into the class that affect any instance that you decide to create. Let's say that you want a new flower to bloom:

You open your class back up and define a method within it:

def bloom(flower_name)

puts "The petals have opened and #{flower_name} is in bloom!"

end

With the above code you have just created a method that will work on each new flower, each new instance of the Flowers class. To make it work on a new instance, call the method on the instance with the flower's name in the parenthesis:

tulip = Flowers.new(8, "pink")
#=> "You made a flower with 8 pink petals."

tulip.bloom("tulip")
#=> "The petals have opened and tulip is in bloom!"

Now taking this template for creating flowers, you can create as many flowers as you want. You can give them all different numbers of petals and colors of petals. All of the flowers created can 'bloom' as well. You can add more methods to the Flowers class so that the instances created can grow, wilt or blow in the breeze.

The point of this, and the beauty of it all, is that you don't have to go and create each new object from scratch. Just go back to your template and plug in the specific characteristics you'd like it to have, and let the template to the work. Each time your daughter comes up and tells you that she wants a new flower, all you have to ask is what color petals and how many petals? Then you will truely be a god, at least in your daughter's eyes.