Ruby Console (Interactive Ruby): irb

Syntax

• http://ruby-doc.org/core-2.3.1/doc/syntax_rdoc.html

Assignment

• http://ruby-doc.org/core-2.3.1/doc/syntax/assignment_rdoc.html

Modules and Classes

• http://ruby-doc.org/core-2.3.1/doc/syntax/modules_and_classes_rdoc.html

Related methods in Ruby can be packaged in modules.

Modules are often explicitly imported or they can be imported automagically in frameworks that favours conventions like ruby on rails.

module ApplicationHelper
	# ....
end

Method definition

• http://ruby-doc.org/core-2.3.1/doc/syntax/methods_rdoc.html

By convention, every method that ends with a question mark ? returns a boolean value.

irb(main):> "".empty?
=> true

Defining a method with def:

def message(str = '')
  return "empty string!" if str.empty?
  return "nonempty."
end

Comments

Comments start with the hash mark # (also called the pound sign and the octothorpe)

# This is a comment in ruby

Local variable assignment

Booleans

Comparisons

• Equality comparison operator ==
• Not equal comparison operator !=

Control flow

• Control Expressions http://ruby-doc.org/core-2.3.1/doc/syntax/control_expressions_rdoc.html

Conditional clause (if)

• http://ruby-doc.org/core-2.3.1/doc/syntax/control_expressions_rdoc.html#label-if+Expression

if-elsif-end

irb(main):> if "".empty? && !"a".empty? || "".length==0 
irb(main):>   puts "YOLO"
irb(main):> elsif !"".empty?
irb(main):>   puts "That is not YOLO"
irb(main):> end
YOLO
=> nil
irb(main):> puts "Hello" if "".empty?
Hello
=> nil

Strings

Strings in Ruby are specified with double quotes "a string" or single quotes'another string'. The main difference between them is that double quotes allows string interpolation "Hello #{name}" and escape sequences "\n" so it is encouraged to use them.

String concatenation is done with + sign: "foo" + "bar" or with interpolation:

irb(main):> sport="running"
=> "running"
irb(main):> "keep #{sport}"
=> "keep running"

Printing

To print a string there is the command puts and print.

The command puts stands for put string and is used to print strings.

irb(main):> print "foobar"
foobar=> nil
irb(main):> puts "foobar"
foobar
=> nil
irb(main):> print "foobar\n"
foobar
=> nil

Return values

Data structures

Arrays

• http://ruby-doc.org/core-2.3.1/Array.html

a = ["foo", "bar", "baz"]

• Access specific array position
  • a[0]
  • a.first

Operator precedence

• http://ruby-doc.org/core-2.3.1/doc/syntax/precedence_rdoc.html

References

• Official Documentation https://www.ruby-lang.org/
• Docs and API http://ruby-doc.org/