ruby and the tools 740tools05 classesobjectsvars

Ruby and the tools740Tools05ClassesObjectsVars

Ruby and the tools740Tools05ClassesObjectsVars

TopicsTopics

Ruby Classes Objects Variables Containers Blocks Iterators

Spring 2014

CSCE 740 Software Engineering

– 2 – CSCE 740 Spring 2014

Tools - Tools -

Last TimeLast Time

Ruby BasicsRuby Basics

Ruby RegexpRuby Regexp

New RubyNew Ruby

ClassesClasses

ObjectsObjects

Next Time: System Modelling Next Time: System Modelling

– 3 – CSCE 740 Spring 2014

Ruby 1.9 “Buy the book page”Ruby 1.9 “Buy the book page”

http://pragprog.com/book/ruby3/programming-ruby-1-9

Contents and ExtractsContents and Extracts

• Regular Expressions (download Regular Expressions (download pdf))

• Namespaces, Source Files, and Distribution Namespaces, Source Files, and Distribution (download (download pdf))

• Built-in Classes and Modules (download Built-in Classes and Modules (download pdf of the of the entry for class Array)entry for class Array)

• Free Content …Free Content …

More on reg exprMore on reg expr

• http://www.ruby-doc.org/core-2.1.0/Regexp.html

http://ruby-doc.org/docs/ProgrammingRuby/

– 4 – CSCE 740 Spring 2014

google(ruby 1.9 tutorial)google(ruby 1.9 tutorial)

• http://ruby-doc.com/docs/ProgrammingRuby/

• http://www.ruby-doc.org/stdlib-1.9.3/ http://www.ruby-doc.org/stdlib-1.9.3/

– 5 – CSCE 740 Spring 2014

Programming Ruby TOCProgramming Ruby TOC

Foreword Preface Roadmap Ruby.new Classes, Objects, and Variables Containers, Blocks, and Iterators Standard Types More About Methods Expressions Exceptions, Catch, and Throw Modules Basic Input and Output Threads and Processes When Trouble Strikes

Ruby and Its World Ruby and the Web Ruby Tk Ruby and Microsoft Windows Extending Ruby The Ruby Language Classes and Objects Locking Ruby in the Safe Reflection, ObjectSpace, and Reflection, ObjectSpace, and Distributed Ruby Distributed Ruby Built-in Classes and Built-in Classes and Methods Methods Standard Library Standard Library Object-Oriented Design Object-Oriented Design Libraries Libraries Network and Web Libraries Network and Web Libraries Microsoft Windows Support Microsoft Windows Support Embedded Documentation Embedded Documentation Interactive Ruby Shell Interactive Ruby Shell SupportSupport

– 6 – CSCE 740 Spring 2014

Regexp: Lookahead and LookbehindRegexp: Lookahead and Lookbehind

– 7 – CSCE 740 Spring 2014

Ruby I/ORuby I/O

• Already seenAlready seen• puts• print • P

• On readingOn reading• Gets reads line from stdin variable $_• Iterate over lines of file

line = gets line = gets

print lineprint line


– 8 – CSCE 740 Spring 2014

Processing stdin = ARGFProcessing stdin = ARGF

while gets while gets # assigns line to $_ # assigns line to $_

if /Ruby/ if /Ruby/ # matches against $_ # matches against $_

print print # prints $_ # prints $_

end end

endend

Now the “ruby way”Now the “ruby way”

ARGF.each { |line| print line if line =~ /Ruby/ }ARGF.each { |line| print line if line =~ /Ruby/ }


– 9 – CSCE 740 Spring 2014

Classes, Objects, VariablesClasses, Objects, Variables

Basic Classes: def, to_sBasic Classes: def, to_s

Inheritance and MessagesInheritance and Messages

Inheritance and MixinsInheritance and Mixins

Objects and AttributesObjects and Attributes

Writable AttributesWritable Attributes

Virtual AttributesVirtual Attributes

Class Variables and Class MethodsClass Variables and Class Methods

Singletons and Other ConstructorsSingletons and Other Constructors

Access ControlAccess Control

VariablesVariables

– 10 – CSCE 740 Spring 2014

Classes, Objects, and VariablesClasses, Objects, and Variables

class Song class Song

def initialize(name, artist, duration) def initialize(name, artist, duration)

@name = name @name = name

@artist = artist @artist = artist

@duration = duration @duration = duration

endend

endend

aSong = Song.new("Bicylops", "Fleck", 260)aSong = Song.new("Bicylops", "Fleck", 260)


– 11 – CSCE 740 Spring 2014


aSong.inspect >> aSong.inspect >> #<Song:0x401b4924 @duration=260, @artist=\"Fleck\", #<Song:0x401b4924 @duration=260, @artist=\"Fleck\", @name=\"Bicylops\">@name=\"Bicylops\">

aSong.to_s >> "#<Song:0x401b499c>”aSong.to_s >> "#<Song:0x401b499c>”


– 12 – CSCE 740 Spring 2014

New improved to_sNew improved to_s


class Songclass Song

def to_sdef to_s

““Song: #{@name} -- #{ @artist } ( #{ @duration } Song: #{@name} -- #{ @artist } ( #{ @duration } )”)”

endend

endend


aSong.to_s >> “Song: Bicylops--Fleck (260)”aSong.to_s >> “Song: Bicylops--Fleck (260)”

– 13 – CSCE 740 Spring 2014

InheritanceInheritance

class KaraokeSong < Song class KaraokeSong < Song

def initialize(name, artist, duration, lyrics) def initialize(name, artist, duration, lyrics)

super(name, artist, duration) super(name, artist, duration)

@lyrics = lyrics @lyrics = lyrics

endend

EndEnd

aSong = KaraokeSong.new("My Way", "Sinatra", 225, "aSong = KaraokeSong.new("My Way", "Sinatra", 225, "And now, the...")And now, the...")

aSong.to_s …aSong.to_s …


– 14 – CSCE 740 Spring 2014

overriding to_soverriding to_s


class KarokeSongclass KarokeSongdef to_sdef to_s

“ “KS: #{@name} -- #{ @artist } ( #{ @duration } KS: #{@name} -- #{ @artist } ( #{ @duration } ) ) [#{@lyrics}]”[#{@lyrics}]”endend

endend

class KaraokeSong < Songclass KaraokeSong < Song def to_s def to_s

super + " [#{@lyrics}]“super + " [#{@lyrics}]“endend

endend

– 15 – CSCE 740 Spring 2014

Accessing instance variablesAccessing instance variables

Class SongClass Song

attr_reader :name, :artist, :durationattr_reader :name, :artist, :duration

attr_writer :durationattr_writer :duration

……

end end


– 16 – CSCE 740 Spring 2014

class JavaSong { // Java code class JavaSong { // Java code

private Duration myDuration; private Duration myDuration;

public void setDuration(Duration newDuration) {public void setDuration(Duration newDuration) {

myDuration = newDuration; myDuration = newDuration;

} }

}}

class Song class Song

attr_writer :duration attr_writer :duration

endend

aSong = Song.new("Bicylops", "Fleck", 260) aSong = Song.new("Bicylops", "Fleck", 260) aSong.duration = 257aSong.duration = 257


– 17 – CSCE 740 Spring 2014

class Song class Song @@plays = 0 @@plays = 0 def initialize(name, artist, duration) def initialize(name, artist, duration)

@name = name @name = name @artist = artist @artist = artist @duration = duration @duration = duration @plays = 0 @plays = 0

end end def play def play

@plays += 1 @plays += 1 @@plays += 1 @@plays += 1

"song: #@plays plays. Total #@@plays plays." "song: #@plays plays. Total #@@plays plays." endend


– 18 – CSCE 740 Spring 2014

Containers, Blocks, and IteratorsContainers, Blocks, and Iterators

ContainersContainers

ArraysArrays

HashesHashes

Implementing a SongList ContainerImplementing a SongList Container

Blocks and IteratorsBlocks and Iterators

Implementing IteratorsImplementing Iterators

Ruby Compared with C++ and JavaRuby Compared with C++ and Java

Blocks for TransactionsBlocks for Transactions

Blocks Can Be ClosuresBlocks Can Be Closures

– 19 – CSCE 740 Spring 2014

ContainersContainers

Hashes

h = { 'dog' => 'canine', 'cat' => 'feline', 'donkey' => 'asinine'

}

h.length » 3

h['cow'] = 'bovine'

h['cat'] = 99

Arrays

a = [ 3.14159, "pie", 99 ]

a.type » Array

a.length » 3

a[2] » 99

50 or so methods

http://www.ruby-doc.org/core-2.1.0/Array.html

– 20 – CSCE 740 Spring 2014

Implementing a SongList ContainerImplementing a SongList Container

append( aSong ) » list append( aSong ) » list

Append the given song to the list. Append the given song to the list.

deleteFirst() » aSong deleteFirst() » aSong

Remove the first song from the list, returning that Remove the first song from the list, returning that song. song.

deleteLast() » aSong deleteLast() » aSong

Remove the last song from the list, returning that Remove the last song from the list, returning that song. song.

[ anIndex } » aSong [ anIndex } » aSong

Return the song identified by Return the song identified by anIndexanIndex, which may be , which may be an integer index or a song title. an integer index or a song title.


– 21 – CSCE 740 Spring 2014

SongList: Initializer & appendSongList: Initializer & append# Initializer# Initializer

class SongList class SongList

def initializedef initialize

@songs = Array.new@songs = Array.new

end end

endend

#append method#append method

class SongListclass SongList

def append(aSong)def append(aSong)

@songs.push(aSong)@songs.push(aSong)

selfself

end end

endendhttp://ruby-doc.org/docs/ProgrammingRuby/

– 22 – CSCE 740 Spring 2014

SongList: Using Array methodsSongList: Using Array methods


def deleteFirstdef deleteFirst

@[email protected]

endend

def deleteLastdef deleteLast

@[email protected]

end end

endend


– 23 – CSCE 740 Spring 2014

SongList: [ ] method 1rst versionSongList: [ ] method 1rst version


def [ ](key)def [ ](key)

if key.kind_of?(Integer)if key.kind_of?(Integer)

@songs[key]@songs[key]

elseelse

# ...# ...

endend

end end

endend

– 24 – CSCE 740 Spring 2014

Class VariablesClass Variables

class Song @@plays = 0class Song @@plays = 0 def initialize(name, artist, duration)def initialize(name, artist, duration) @name = name@name = name @artist = artist@artist = artist @duration = duration@duration = duration @plays = 0@plays = 0 endend def playdef play @plays += 1@plays += 1 @@plays += 1@@plays += 1 "This song: #@plays plays. Total #@@plays plays."This song: #@plays plays. Total #@@plays plays. endendendend

– 25 – CSCE 740 Spring 2014

Class MethodsClass Methods

class Example class Example

def instMeth def instMeth # instance method # instance method

……

end end

def Example.classMeth def Example.classMeth # class method # class method

……

end end

endend


– 26 – CSCE 740 Spring 2014

SingletonsSingletons

class Logger class Logger

private_class_method :new private_class_method :new

@@logger = nil @@logger = nil

def Logger.create def Logger.create

@@logger = new unless @@logger @@logger = new unless @@logger

@@logger @@logger

end end

endend


Logger.create.id » 537766930 Logger.create.id » 537766930

– 27 – CSCE 740 Spring 2014

Access Control Access Control

““Public methods can be called by anyone---there is no Public methods can be called by anyone---there is no access control. Methods are public by default access control. Methods are public by default (except for initialize, which is always private). (except for initialize, which is always private).

Protected methods can be invoked only by objects of Protected methods can be invoked only by objects of the defining class and its subclasses. Access is kept the defining class and its subclasses. Access is kept within the family. within the family.

Private methods cannot be called with an explicit Private methods cannot be called with an explicit receiver. Because you cannot specify an object when receiver. Because you cannot specify an object when using them, private methods can be called only in using them, private methods can be called only in the defining class and by direct descendents within the defining class and by direct descendents within that same object.”that same object.”


– 28 – CSCE 740 Spring 2014

Specifying Access Specifying Access class MyClass class MyClass def method1 def method1 # default is 'public' # default is 'public'

#... #... end end

protected protected # subsequent methods will be 'protected' # subsequent methods will be 'protected' def method2 def method2 # will be 'protected' # will be 'protected'

#... #... end end

private private # subsequent methods will be 'private' # subsequent methods will be 'private' def method3 def method3 # will be 'private' # will be 'private'

#... #... end end

public public # subsequent methods will be 'public' # subsequent methods will be 'public' def method4 def method4 # and this will be 'public' # and this will be 'public'

#... #... end end

endend


– 29 – CSCE 740 Spring 2014

BlocksBlocks

a = %w( ant bee cat dog elk ) # create an array a = %w( ant bee cat dog elk ) # create an array

a.each { |animal| puts animal } # iterate over the contentsa.each { |animal| puts animal } # iterate over the contents

Yield – will be discussed next timeYield – will be discussed next time

[ 'cat', 'dog', 'horse' ].each do |animal| [ 'cat', 'dog', 'horse' ].each do |animal|

print animal, " -- "print animal, " -- "


– 30 – CSCE 740 Spring 2014

{ puts "Hello" } # this is a block { puts "Hello" } # this is a block

do #do #

club.enroll(person) # and so is this club.enroll(person) # and so is this

person.socialize person.socialize

endend


– 31 – CSCE 740 Spring 2014

BlocksBlocks

5.times { print "*" } 5.times { print "*" }

3.upto(6) {|i| print i } 3.upto(6) {|i| print i }

('a'..'e').each {|char| print char }('a'..'e').each {|char| print char }

*****3456abcde*****3456abcde


– 32 – CSCE 740 Spring 2014

the [ ] method the [ ] method


def [](key)def [](key)


return @songs[key]return @songs[key]

elseelse

for i in [email protected] i in [email protected]

return @songs[i] if key == @songs[i].namereturn @songs[i] if key == @songs[i].name

endend

endend

return nilreturn nil

end end

endend

– 33 – CSCE 740 Spring 2014

the [ ] method version 2the [ ] method version 2


def [](key)def [](key)


result = @songs[key]result = @songs[key]

elseelse

result = @songs.find { |result = @songs.find { |aSong| key == aSong.name aSong| key == aSong.name } } endend

return resultreturn result

end end

endend

– 34 – CSCE 740 Spring 2014

the [ ] method version 3the [ ] method version 3

class SongList class SongList

def [](key) def [](key)

return @songs[key] if key.kind_of?(Integer) return @songs[key] if key.kind_of?(Integer)

return @songs.find { |aSong| aSong.name == key } return @songs.find { |aSong| aSong.name == key }

end end

endend

– 35 – CSCE 740 Spring 2014

Implementing IteratorsImplementing Iterators

def callBlockdef callBlock

yieldyield

yield yield

end end

callBlock { puts "In the block" }callBlock { puts "In the block" }

ProducesProduces

In the blockIn the block

In the blockIn the blockhttp://ruby-doc.org/docs/ProgrammingRuby/

– 36 – CSCE 740 Spring 2014

def fibUpTo(max)def fibUpTo(max)

i1, i2 = 1, 1 # parallel assignmenti1, i2 = 1, 1 # parallel assignment

while i1 <= maxwhile i1 <= max

yield i1yield i1

i1, i2 = i2, i1+i2i1, i2 = i2, i1+i2

end end

end end

fibUpTo(1000) { |f| print f, " " }fibUpTo(1000) { |f| print f, " " }

produces 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987produces 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987

– 37 – CSCE 740 Spring 2014

class Array

def find

for i in 0...size

value = self[i]

return value if yield(value)

end

return nil

end

end

[1, 3, 5, 7, 9].find {|v| v*v > 30 } >> 7

– 38 – CSCE 740 Spring 2014

[ 1, 3, 5 ].each { |i| puts i }[ 1, 3, 5 ].each { |i| puts i } >>>> 1 3 51 3 5

["H", "A", "L"].collect { |x| x.succ } ["H", "A", "L"].collect { |x| x.succ }

»

["I", "B", "M"]

– 39 – CSCE 740 Spring 2014

Ruby Compared with C++ and JavaRuby Compared with C++ and Java

– 40 – CSCE 740 Spring 2014

Blocks for TransactionsBlocks for Transactions

class File class File

def File.openAndProcess(*args) def File.openAndProcess(*args)

f = File.open(*args) f = File.open(*args)

yield f yield f

f.close() f.close()

end end

end end

File.openAndProcess("testfile", "r") do |aFile| File.openAndProcess("testfile", "r") do |aFile|

print while aFile.gets print while aFile.gets

endend

– 41 – CSCE 740 Spring 2014

class File class File

def File.myOpen(*args) def File.myOpen(*args)

aFile = File.new(*args) aFile = File.new(*args)

# If there's a block, pass in the file and close # If there's a block, pass in the file and close

# the file when it returns # the file when it returns

if block_given? if block_given?

yield aFile yield aFile

aFile.close aFile.close

aFile = nil aFile = nil

end end

return aFile return aFile

end end

endend

– 42 – CSCE 740 Spring 2014

Blocks Can Be ClosuresBlocks Can Be Closures

bStart = Button.new("Start") bStart = Button.new("Start")

bPause = Button.new("Pause")bPause = Button.new("Pause")

class StartButton < Button class StartButton < Button

def initialize def initialize

super("Start") # invoke Button's initialize super("Start") # invoke Button's initialize

end end

def buttonPressed def buttonPressed

# do start actions... # do start actions...

end end

end end

bStart = StartButton.newbStart = StartButton.new

– 43 – CSCE 740 Spring 2014

class JukeboxButton < Button class JukeboxButton < Button

def initialize(label, &action) def initialize(label, &action)

super(label) super(label)

@action = action @action = action

end end

def buttonPressed def buttonPressed

@action.call(self) @action.call(self)

end end

end end

bStart = JukeboxButton.new("Start") { songList.start }bStart = JukeboxButton.new("Start") { songList.start }

bPause = JukeboxButton.new("Pause") { songList.pause }bPause = JukeboxButton.new("Pause") { songList.pause }

– 44 – CSCE 740 Spring 2014

def nTimes(aThing)

return proc { |n| aThing * n }

end

p1 = nTimes(23)

p1.call(3) » 69

p1.call(4) » 92

p2 = nTimes("Hello ")

p2.call(3) » "Hello Hello Hello "

ruby and the tools 740tools05 classesobjectsvars

Documents