Ruby Foundations
This lesson discusses the basics of the ruby language
Topics
Objects & Methods
- In Ruby, all data are objects:
- Every object is a member of some class.
- Every object has a method called
.class which will tell you what it is
"hello".class
=> String
8.3.class
=> Float
[4, 8, 15].class
=> Array
- The class that an object belongs to determines what it can do. (i.e., what methods we can call on it)
- We attach the method name to the object with a dot.
# String#capitalize
"ian".capitalize
=> "Ian"
# String#length
"ian".length
=> 3
# Float#round
8.3.round
=> 8
# Float#ceil
8.3.ceil
=> 9
# Array#sort
[3, 2, 1].sort
=> [1, 2, 3]
# Array#length
[4, 8, 15].length
=> 3
- Methods return a value, which is, like everything, an object; perhaps of the same class as the original object, perhaps not.
# returns another Array
[4, 8, 15].reverse
=> [15, 8, 4]
# returns an Integer
[4, 8, 15].length
=> 3
- 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 more!
- 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?”
- 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.
Resources