Variables

Agenda

• What they are used for
• What do they look like
• Standard look

What are they used for?

Variables are a central part of any programming language and Ruby is no different. Variables are a way to store dynamic values for later. The main idea behind this is that you can then store a value in it and any time you call upon that you can retrieve that value. That stored value is free to modified at your discretion.

Let’s define some terms first.

• variable - the entity used to store values or in ruby’s case objects!
• assignment - the action of saving to the variable
• access - getting the value from a variable

I can talk about how this is valuable but let’s try an example.

x = 5 #=> 5 # assignment
x = x + 5 #=> 10 # Reassignment
x #=> 10

What do they look like?

Variables come in all shapes and sizes. But there are some rules for them. A variable is anything word starting with character from the alphabet or $ or _ or @. And the rest can be any combination of alphanumeric characters of any case and _ .

• variable
• @variable
• @@variable
• VARIABLE
• Variable = Class.new
• $variable

This is sort of all over the place. But there are standards for this. Most variables are going to be what’s called snake_case. Or as it looks all lower case where new words are separated by an underscore. Here are the guidelines typically for variables.

The regular variable

Most variables with snake it’s used only by the methods you they are created in. They are meant to have very limited mobility/scope. Here’s an example.

@instance_variable

This one is just like other last variable is in snake case, but an entire object knows about this variable. Let me give an example.