Ruby Foundations

Objects & Methods

In Ruby, all data are objects:
​"hello" 8.3 [4, 8, 15]

Every object is a member of some class.
​String Float Array

The class that an object belongs to determines what it can do
(i.e., what methods we can call on it)
String#capitalize String#length Float#round Float#ceil Array#sort Array#length

Objects & Methods

We attach the method name to the object with a dot.

[4, 8, 15].length
=> 3

Every object has a method called .class which will tell you what it is

[4, 8, 15].class
=> Array

Objects & Methods

Methods return a value, which is, like everything, an object; perhaps of the same class as the original object, perhaps not.

[4, 8, 15].reverse # => another Array

[4, 8, 15].length # => an Integer

The return value replaces the original expression in the program, and then the program continues.

[4, 8, 15].length.odd? # => true

First Letters

The first letter of each word, or token, in a program is how Ruby determines what it is:

lowercase letter: local variable
(unless it's one of a handful of keywords like if, elsif, else, def, do, self, class, end; and a few others that we won't use)

digit: an Integer or Float

"double" or 'single' quotes: a String literal

[square brackets]: an Array literal

{curly braces}: a Hash literal

:colon: a Symbol

CapitalLetter: a class

What Kind of Thing?

The most important things you should be asking yourself are:

"What class is the object that I have?"
"What methods does it have?"
"Which method will get me one step closer to my goal?"

It doesn't matter what class of object you wish you had. It only matters what you actually have. Your job is to invent a way to get from your starting point to your goal, using the tools at hand.

Sometimes Ruby or a third-party library will have a method that will get you 90% of the way. Most of the time, you'll have to do the work yourself using the fundamental building blocks of any program:

Building Blocks

Expressions: object.method(argument) # => returns a value
Variables: to save the results of expressions variable = object.method(argument)
Conditionals: if statements
Loops

That's all we need for now. We can build anything with these.

We Are Inventors

When you signed up to learn how to program, you signed up to become an inventor.

Software developers tackle unsolved problems.

There aren't predefined solutions to look up and apply.

Otherwise, we'd just buy something off the shelf and be software users.

When faced with a task, your first instinct should be: "How can I solve this puzzle with the tools I have?"

We Are Inventors

Your first instinct shouldn't be: "Let me Google for a solution to this problem."

Developers do a lot of that, of course, but only after we've tried to solve it with what we already have.

"Google Fu" is a hugely important skill to practice in software development. But, the answers you find may not be suitable for beginners; they may even slow you down.

The tasks assigned in Yet Another Ruby Introduction are achievable using the classes, methods, and keywords introduced in the Ruby Chapters. Your job is to invent a combination of them that gets the job done.

For now, ask us questions — we are your Google.