Ruby Course - Lesson 1 - Introduction to Ruby

8/8/2019 Ruby Course - Lesson 1 - Introduction to Ruby

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Introduction toRuby

Lesson 1

Saturday, September 11, 2010


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Philosophybehind Ruby



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Humanoriented



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Principle of least surprise



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Fun to program in



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Features of Ruby



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Everything is an object1. class # => Fixnum' a '. class # => String: z . class # => Symbol

class PersonendPerson . class # => Class

Person . new. class # => Person



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On the y

def double_it ( input )

input * 2enddouble_it ( 1) # => 2double_it (" a") # => "aa"



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Open for changeclass Array def first_half slice( 0, size / 2)

endenda = [ 1, 2, 3, 4, 5, 6]puts a. to_s #=> 123456

puts a. first_half . to_s #=> 123



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Program your programs

class Person attr_accessor :first_name , :last_name

attr_reader :person_id alias :last_name , :family_nameend



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Express yourself

me = people. find { |p| p. first_name ==' Sau Sheong ' }

family = people. select { |p| p. last_name == ' Chang ' }



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Perl

SmallTalkLispRuby

+



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Current versions of Ruby



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Matz Ruby InterpreterRuby 1.8.7



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Yet Another Ruby VM-> Ruby 1.9.1



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JRuby (1.4)Ruby 1.8 (1.9) on the JVM



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RubiniusRuby 1.8 in Ruby

(and a bit of C++)



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IronRuby (0.9.2)Ruby 1.8



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MacRuby (0.6)Ruby 1.9 in Objective-C



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Installing Ruby



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http://www.ruby-lang.org/en/downloads/

Windows - RubyInstaller

Mac - already pre-installed (1.8.7); oruse port

Linux (Debian, Ubuntu etc)% sudo apt-get install ruby1.9.1-full

http://www.ruby-lang.org/en/downloads/http://www.ruby-lang.org/en/downloads/http://www.ruby-lang.org/en/downloads/


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Tools



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Rubygems



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Interactive Ruby(irb)



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Language



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Strings and Variables

' Hello, Sau Sheong! '

name = ' Sau Sheong ' # => "Sau Sheong"" Hello, #{ name}! " # => "Hello, Sau Sheong!"



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Methodsstr = " Hello, World! " # => "Hello, World!"str . size # => 13str . sub (" World ", " Ruby") # => "Hello, Ruby!"

def greet ( name=" Sau Sheong ")

" Greetings, #{ name}! "end

puts greet

puts greet (' everyone ')# >> Greetings, Sau Sheong!# >> Greetings, everyone!



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Numbers

1 + 2 # => 31 + 2.1 # => 3.1

2**10 # => 10249 / 2 # => 45 % 3 # => 2- 3. abs # => 31. class # => Fixnum( 2** 50). class # => Bignum1.3 . class # => Float



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ArraysArray . new # => [][ 1, 2, 3] # => [1, 2, 3][ 1] + [ 2] [1, 2, 3][ 1, 2, 3] - [ 2, 3] # => [1]%w(one two ) # => ["one", "two"][ 1, 2, 3]. pop # => 3[ 1, 2]. push ( 3) # => [1, 2, 3]

[ 1, 2, 3]. shift # => 1[ 2, 3]. unshift ( 1) # => [1, 2, 3][ 1, 3]. insert ( 1, 2) # => [1, 2, 3]



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Hashes

options = {: name => " Ruby"}

h = Hash . new # => {}h[' string '] = 1h[: symbol ] = 1h # => {:symbol=>1, "string"=>1}

h. keys # => [:symbol, "string"]h[: symbol ] # => 1



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Iterators

for n in 0.. 2puts n

end

( 0.. 2). each do | n|puts n

end

[ 0, 1, 2]. each {| n| puts n }



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Enumerable

ary = [ 1, 2, 3]

ary . map {| n| n * 2} # => [2, 4, 6]ary . select {| n| n % 2 == 0} # => [2]ary . inject ( 0) {| sum, n| sum + n} # => 6



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Control structuresif some_condition # ...elsif other_condition # ...else # ...end

while condition # ...end

puts " lol " if funny?



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Regular Expressionsstr = " Hello, world! "str . gsub (/[ aeiou ]/," *") # => "H*ll*, w*rld!"str =~ / w( or ) ld / # => 7

$1 # => "or"match = str . match (/ w( or ) ld /) # => #match [ 0] # => "world"match [ 1] # => "or"



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Error handlingbegin raise " Standard error "rescue => e

p eend# >> #

begin raise StandardError . new(" Oh, oh ")rescue RuntimeError

puts " runtime "rescue StandardErrorputs " standard "

end# >> standard



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Files

File . open (' test.txt ',' w') do | file |file . write (" line \n ")file . puts (" line ")

endFile . read (' test.txt ')



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Classesclass Calc attr_accessor : factor

def initialize ( factor =2) @factor = factor end

def multiply ( value ) @factor * value endend

calc = Calc . newcalc . multiply 5 # => 10calc . factor = 3calc . multiply 5 # => 15



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Inheritanceclass Foo def greet " Hi, #{ value }" end def value " foo "

endend

class Bar < Foo def value " bar " endend

Foo . new. greet # => "Hi, foo"Bar . new. greet # => "Hi, bar"



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Class methodsclass Foo def self.bar " BAR!" end

def bar " bar " endend

Foo . bar # => "BAR!"Foo . new. bar # => "bar"



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Mixinsmodule Even def even? self % 2 == 0

endend

class Fixnum include Evenend

1. even? # => false2. even? # => true



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Questions?

Documents

Ruby Course - Lesson 1 - Introduction to Ruby