| Comments

Ruby Programming Languages

AB2014 – Ruby101 for beginners

These notes restored in Academic Information Education Mersin from Notes of Mr. Sıtkı Bagdat .

Ruby is a programming languages

  • Ruby, readable high level a programming languages.
  • Started to developt at 1993 and published at 1995.
  • In 2013 for Ruby was selected brightest year,the reason is that in this year, two version was developt Ruby-2.0 and Ruby-2.1.
  • Ruby, entegration with Rails in 2004.Then we start to use Ruby on Rails in web development.
  • Ruby developt by Japon Yukihirato Matsumoto (Matz).
  • Ruby is completely object-oriented. (With a few exceptions)
  • Unlike another programming languages, ruby is interpreter languages. This means that, when we developt programm with ruby if can find a bug, Ruby running until bug’s line.
  • Included dynamic typing. This means that, we goes easily from a type to another type, not necessary to pre-definition.
  • Ruby included package managers. (RubyGems)
  • Ruby provide to development to Ruby on Rails and Sinatra .

also

  • Metaprogramming (Coding write code.)
  • DSL (Domain Specific Language)
  • DRY (Don’t repeat yourself)
  • TIMTOWTDI (There is more than one way to do it)

Ruby.philosopy[]

  • Ruby.philosopy[1]

Ruby is, stronger than Perl, more object-oriented than Phyton, script languages.

Perl + Smalltalk + Phyton + Lisp + Ada + … = Ruby

  • Ruby.philosopy[2]

Ruby like a human body, seemingly simple but there are a complex structure inside.

  • Ruby.philosopy[3]

The aim is, When we coding a programming, coding should provide to express simple and readable.

Irb ve Repl Functions

1
2
3
4
5
6
7
8
9
10
11
12

irb
irb(main):001:0> 2+2
=> 4
exit
irb --simple -prompt
>> 12.class
=> Fixnum
>> exit
irb(main):003:0> 2*9/3+7
=> 13
irb(main):004:0> _ * 3
=>39

Acoording to above irb, opened ruby terminal; exit exit to ruby terminal. In addition irb —simple -prompt this command is provide to seeming regular to terminal.Strikes the eye another notifications is that

_

this sign provide to take pre-functions and then make process with this functions.

1

system('clear')

with this command provide to clear your terminal.

1
2

irb(main):008:0> self
=> main

this command show the writing on main class .

Also

1
2
3
4
5
6
7

irb(main):010:0> a="Ruby"
=> "Ruby"
irb(main):011:0> a.reverse
=> "ybuR"
irb(main):012:0> "I love
irb(main):013:0" ruby"
=>  "I love\nruby

Seeming to above code .reverse method which entered code, provide to writing reverse.Also if when opened quotes then not closed, > instead “ can be this expression.

Logical expressions

  • False or nil, acceptable false.
  • Except false ve nil, everything acceptable true, like 0, [], …
  • Like another languages, when we make comparisons <,>, ==,! using this expressions.
1
2
3
4
5
6
7
8
9
10
11
12
13
14

irb(main):001:0 3 > 5
=> false
irb(main):002:0 3 < 5
=> true
irb(main):003:0 3 == 5
=> false
irb(main):004:0 !13
=> false
irb(main):005:0 true.class
=> TrueClass
irb(main):006:0 false.class
=> FalseClass
irb(main):007:0 nil.class
=> NilClass

We mention to everthing an object and derivation from a class in Ruby, strike to eye above, True, false , nil derivation a class. Also we mention about nil, nil means that nothing like another languages null, undefined…etc. In ruby, Not exist relevant to logical expression like Boolean or Bool classes. Also While we are using to logical expression, using like &&, ||, ! (and, or, not) expression.

Meeting to Methods

  • Defining to method start def, and ending with end.
1
2
3

def method_name
...
end

If method get a parameter like :

1
2
3

def method_name(param1)
...
end

1
2
3

def method_name(param1, param2)
...
end

Also Not required to using parenthesis like :

1
2
3

def method_name param1, param2, ...
...
end

1
2
3
4

def collection number1, number2
    number1 + number2
end
puts "Result of collection: ", collection(3,5)

The above codes writing in .rb file and then save it, then open your terminal , writing path of files in terminal

1

ruby project_name

write above command in terminal.

In Above code, defining collect method for collection two number and make collection process then show in terminal.

  • Method name, ending with ?, ! or = ,this characters have special meaning.
1

questioning?    #return true or false

1

changed_value = ...   #changed value of anything value, assignment operator.

1

danger!    #changed original text.

1
2
3
4
5
6
7
8
9
10
11

irb(main):001:0> a="Ruby"
=> "Ruby"
irb(main):002:0> a.reverse
=> "ybuR"
irb(main):003:0> a
=> "Ruby"
>> exit
irb(main):004:0> a.reverse!
=>  "ybuR"
irb(main):005:0> a
=>  "ybuR"

In above example entering a value and using ! character changed original value.

Rules for named

  • class, module and constant name starts with capital letter.
1
2
3
4
5
6
7

class ClassName
...
end
module ModuleName
...
end
PI_CONSTANT = 3,14156

must be defined like above. Also you know constants doesn’t change, if you want to change can be bug.

1
2
3
4
5
6

irb(main):001:0> PI_CONSTANT = 3,14156
=> [3,14156]
irb(main):002:0> PI_CONSTANT  = 2
(irb):47: warning: already initialized constant PI_CONSTANT
(irb):46: warning: previous definition of PI_CONSTANT  was here
=> 2
  • local variables starting with lover letter or ‘_’ , like :
1
2

local_variable = "like this."
plate = 20
  • Global variables starting with ‘$’, like :
1

$global_variables
  • instance variables starting with ‘@’ and class variables starting with ‘@@’. like :
1

@instance_variables

1

@@class_variables

Also you can writing ruby, without opening irb in terminal. like:

1
2

ruby -e "puts 'Hello'"
=> Hello

But the above method is not a preferred method commonly.

1
2
3
4
5

def changed(value)
    variables = value
end
puts "Value of variables: #{changed(20)}"
=> Value of variables: 20

included another file in your file.

external_file.rb can be ruby file like this.Also can be we are currently working on calıstıgımız_dosya.rb.

If we want to embeded in external_file.rb files on currently_working_file.rb files, we should use load comand. like :

1

external_file.rb

1
2

currently_working_file.rb
load 'external_file.rb'

In Rails, we can generally use autoload command. autoload is loading automatically file.

Instead of load command, you can use require command but,when you use load, you can use many times in file, when you use require, require load file only once and generally require more preferred than it. In addition, If we use ruby library, we should use, like

1

require 'library_name'

You can see to use all path and method with ENV

Writing command about Gem :

1
2
3
4
5
6
7

gem -v       #seeing the version of gem
gem update --system  #provide to update your system
gem list      #you can see all gem list
gem list -r   #will see load to gem
gem install pry   #provide to writing colorful in terminal.
gem install pry --no-ri   # thanks to this we can install without documentation.
gem uninstall package_name    #use for uninstall gem

If you use package ,before need to install the package, using this command

1

gem install package_name

when we install this gem, then we embeded in currently_working_file.rb like

1

require 'package_name'

If I use many gem, Do I install gem one by one?

Of course No!, instead of this we use Gemfile, we write in file

1
2

source ('http://ruby-gems.org')
gem 'package_name'

we write above command in Gemfile, we install automatically all gems.

Also If I create a ruby file, go to wanted directory and write below code, These code provided create ruby file in Desktop.

1
2
3

gem install bundler
cd Desktop        #for desktop path
bundle gem package_name

For detail viewing Bundler

Opened file, after we make to do, push to package to RubyGems then we see in this site.

Note : -Also Thor is a package(gem) for ruby. –ARGV is constant which hidden to arguments. -In documentation section writing ri command, generally we use to search for method.

1

ri Class#method

Input – Output processing

For output command write like

1
2
3
4

puts     # output with \n.
print
p         #when we use '.inspect', instead of *.inspect* we use *p*.
printf

For input command write like

1

gets     #get input from user.

above instead of p using .inspect

1
2

puts "ruby".inspect
puts 3.inspect

.inspect method provide to take hid state of method. This means that if I using .inspect instead of this using p.

  • chomp provide if the last character can exist “\n” symbol, cleaning the last characters.

  • chom provide to clean all last characters

                 Basic Object
                  ||
                Object
                  ||
                Numeric
                  ||
  Integer     float   Rational    Complex

    Fixnum Bignum

If you generally showing the class, you can show like above.

  • In Ruby 2.0 version, if you want to defining rational number, you can like 30/2r.
  • In Ruby monetary system should use BigDecimal library in project.
1
2
3
4

1.0e7          #10.000.000
3.methods       #for 3 number, bring all methods
require 'yaml'            # added yaml .
puts 2.methods.to_yaml
  • <=>(space ship) comparative operator.
1
2
3
4

a <=> b
a < b ; -1
a > b ; 1
a =b ; 0

1
2

a = 5 && b = 10
a <=> b            #-1

-times and upto methods

1
2
3

10.times do |i|
...
end

or

1

10.times {|i| ...}

thanks to this we write loop with times.

1
2
3
4
5
6
7
8
9
10
11
12
13
14

irb(main):001:0> 10.times do |i|
irb(main):002:1* puts "ruby"+i.to_s
irb(main):013:1> end
ruby0
ruby1
ruby2
ruby3
ruby4
ruby5
ruby6
ruby7
ruby8
ruby9
=>10
  • With 1.upto(10){…} same use with times
1
2
3
4
5
6
7
8
9
10
11
12

irb(main):001:0> 10.upto(10) {puts "ruby"}
ruby
ruby
ruby
ruby
ruby
ruby
ruby
ruby
ruby
ruby
=>1

or

1
2
3
4
5
6
7
8
9
10
11
12
13
14

irb(main):001:0> 1.upt0(10) do |i|
irb(main):002:1* puts "Ruby"+i.to_s
irb(main):013:1> end
Ruby1
Ruby2
Ruby3
Ruby4
Ruby5
Ruby6
Ruby7
Ruby8
Ruby9
Ruby10
=> 1

Text

  • When we combine the text, we can embed in string expressions.

    “` ruby puts “#{‘academic’.capitalize} #{‘information’.upcase}”

      =>  Academic INFORMATION

    “`

-Also to support Turkish characters, you should use Unicode-Utils library.

1

gem install unicode_utils

install than, write in file,

1

require 'unicode_utils'

1
2

UnicodeUtils.upcase("ruby")
=> RUBY

–%q => use for single quotation

1
2

text = %q<Hello>
=> 'Hello'

–%Q => use for double quotation

1
2

text=%Q{Hello}
    => "Hello"

1
2

irb(main):002:0> ?a
=> "a"
  • Everything can embed in texts.
1
2
3

puts "Everything can embed in text #{def name
$name.capitalize + " "+$surname.upcase
end} puts "My name #{name}""

1
2
3
4
5
6
7

name="Ruby"
surname="Rails"
text = << ANYTHING
I'm long text
#{$name} #{$surname}
ANYTHING
p text

*

1

swapcase

this command translate from lower case to uppercase.

*

1

puts text.split.inspect

Try above method.

1
2

text.sub 'm', 'a'    #translate "m=>a"
text.gsub  'm',  'a'      #translate all  from "m" to "a" .
  • For Convert to Integer
1

.to_i
  • For Convert to String
1

.to_s
  • For Convert to Array
1

.to_a
  • For Convert to Hash
1

.to_h

Symbols

  • When we create symbol like,
1

:symbol_name
  • If content of text is changing generally, using symbol can be difficult, but using for constant process can be easy.
1

object_id

Try command

-For Convert to Symbol

1

.to_sym

Regular expression

  • Regular expression
1

/ ... /

writing in this tag.

1
2

{2, 5}      #this means min 2, max 5.
/.{2,5}/ =~  # when we write "john", "john" between 2 and 5.

1
2
3

^a$b => starting with a, ending with b.
(+) => how many
[^0-9] if not number write it '^' this means that 'not'.

1
2

[A-Za-z0-9_] = \w       #word character
[Â-Za-z0-9_] = \W         #not a word character

1
2
3

exp1 = /.*\.$/         #this means ending with '.'
exp2 = Regexp.new('^[a-z]+$')      #this means that starting with a ending with z.
exp3 = %r{^[a-z]+$}         #starting with a but not ending with z.

Comments