Ruby Tutorial for Beginners

8/3/2019 Ruby Tutorial for Beginners

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Ruby for the Attention Deficit Disorder Programmer - let's start learning Ruby fast!

"Java is a pair of scissors, Ruby is a chainsaw."

1. Install Ruby

For windows you can download Ruby from http://rubyforge.org/frs/?group_id=167 for

Linux try http://www.rpmfind.net.

2. Our first program

Enter the following into the file, "test.rb".

puts "Howdy!"

At the C: prompt enter,

C:>ruby test.rb

This produces:

Howdy!

OK, daylight's burning, let's move on.

3. Output in Ruby

"puts" writes to the screen with a carriage return at the end."print" does the same thing without the carriage return."printf" formats variables like in C and Java 5.

puts "puts works"puts " with line breaks."

print "print works"print " with no line breaks."

printf("\n\nprintf formats numbers like %7.2f, andstrings like %s.",3.14156,"me")

This produces:

puts workswith line breaks.print works with no line breaks.

printf formats numbers like 3.14, and strings likeme.

4. Reading from the Console

Use "gets"
http://rubyforge.org/frs/?group_id=167http://www.rpmfind.net/http://rubyforge.org/frs/?group_id=167http://www.rpmfind.net/


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puts "What is your name?"$name = STDIN.getsputs "Hi "+$name

5. Functions1. Our first Ruby function

'def' starts the definition of a method, and 'end' ends it - no cute little curly braces.

def welcome(name)puts "howdy #{name}" # inside double quotes, #{ } will

evaluate the variableendwelcome("nana") # traditional parens

This Produces:

howdy nana

2. Parentheses are optional3. def welcome(name)4. puts "howdy #{name}" # inside double quotes, #{ } will

evaluate the variable5. end6. welcome "visitor" #look, ma, no parentheses

This Produces:

howdy visitor

The same is true of methods without arguments

"hello".upcase() => "HELLO""hello".upcase => "HELLO"

7. How to return values from a function

We can use the faithful 'return'

def multiply(a,b)product = a * breturn product

endputs multiply(2,3) =>6

Oddly enough you can leave out the "return" statement, and Ruby will helpfullyreturn the last expression:

def mult(a,b)product = a * b

endputs mult(2,3)

or even simpler, leave out "product" and ruby returns the contents of the last

expression:

def mult(a,b)a * b


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endputs mult(3,3) =>9

8. Optional argument values

Ruby lets you assign values to arguments which may, or may not be supplied asshown below:

def test(a=1,b=2,c=a+b)puts "#{a},#{b},#{c}"

endtest => 1,2,3test 5 => 5,2,7test 4, 6 => 4,6,10test 3, 4, 6 => 3,4,6

9. Extra arguments

Extra arguments are gathered into the last variable if preceded with a "*". ("each"

is an iterator that loops over its members).

def test(a=1,b=2,*c)puts "#{a},#{b}"c.each{|x| print " #{x}, "} # We will learn about "each" very

soon. I promise.endtest 3, 6, 9, 12, 15, 18

This produces:

3,6

9, 12, 15, 18,

10. Multiple return values11. def getCostAndMpg12. cost = 30000 # some fancy db calls go here13. mpg = 3014. return cost,mpg15. end16. AltimaCost, AltimaMpg = getCostAndMpg17. puts "AltimaCost = #{AltimaCost}, AltimaMpg = #{AltimaMpg}"

Produces:

AltimaCost = 30000, AltimaMpg = 30

6. Open Classes

You can add methods to existing library classes. For example, in C# 2.0, Microsoft addedthe very helpful string function, IsNullOrEmpty() which replaces the unwieldly construct:if(mystring != null && mystring != "")In Ruby you don't have to wait for the mavens in Redmond to decide you need a newstring function, you can add it yourself.

class Stringdef NullOrEmpty?(self == nil || self == "")end


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endputs "test".NullOrEmpty?puts "".NullOrEmpty?

Is this way cool? Yes. Is this very dangerous? Yes. Remember, Ruby is a chainsaw.

7. Variable naming

Ok, let's slow down and learn some basics about variable names

1. Global variables start with '$'2. Class variables start with '@@'3. Instance variables start with '@'4. Local variables, method names, and method parameters start with a lower case

letter5. Class names, module names and constants start with an uppercase letter6. Variables names are composed of letters, numbers and underscores7. Method names may end with "?", "!", or "=". Methods ending with a "?" imply a

boolean operation (eg, "instance_of?"). Methods ending with "!" imply somethingdangerous, like strings being modified in place (eg, "upcase!")

8. Interesting tidbits about Ruby,1. '#' is the line comment character, all characters after this are ignored. Confusingly

'#' can appear within quotes with a different meaning.2. No semi-colons are needed to end lines, but may be used to separate statements on

the same line3. A backslash (\) at the end of a line is used for continuation4. Indenting is not significant, unlike python5. Types of variables do not need to be declared6. Lines between =begin and =end are ignored7. Lines following "__END__" on its own line with no white space, are ignored8. A tiny demonstration of these:9. # sample program showing special characters like comments10. # I'm a comment line11. a = 1 #notice no semicolon and no type declaration12. b = 2; c = 3 #notice two statements on one line13. name = "Abraham \14. Lincoln" # a line continued by trailing \15. puts "#{name}"16. =begin17. I'm ignored.18. So am I.

19. =end20. puts "goodbye"21. __END__22. 123. 224. 325. 426. Abraham Lincoln27. goodbye

9. Variable Types

In Ruby, variables don't have a specific type associated with them. All variables areobjects, so we only play with pointers to those objects, and those pointers are typeagnostic.

10. bat = "Louisville slugger"


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11. bat = 1.23

12.13. Quotes

Like in Perl, single quotes and double quotes have different meanings.

Double quotes means "please interpret special characters in this string". Things like

backslash n ('\n') are converted to their typical values. The #{name} construct is convertedto its value.

With single quotes, no special characters are interpreted.

Examples:

name="Mike"puts "hi #{name}" =>hi Mikeputs "hi\n #{name}" => hi (carriage return)Mikeputs 'hi\n #{name}' => hi\n #{name} (no substitutions are made since

using single quote)

The braces are optional for global and instance variables

$myname="Ishmael"puts "hi #$myname" =>hi Ishmael

14. Objects

A great thing about Ruby is that numbers and strings are real objects.

1.5.floor() => "1"

This lets us do some cool things. Instead of

if( x > 7 && x < 12 ) { ... }

We can write

if x.between?(7,12) do ...

15. Big Numbers

Ruby automatically increases the precision of variables

for i in 1..1000puts "2 ** #{i} = #{2**i}"

end

Produces:

2 ** 1 = 22 ** 2 = 42 ** 3 = 82 ** 4 = 162 ** 5 = 322 ** 6 = 642 ** 7 = 1282 ** 8 = 256


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2 ** 9 = 5122 ** 10 = 1024...2 ** 1000 =107150860718626732094842504906000181056140481170553360744375038837035105112493612249319837881569585812759467291755314682518714528569231404359845775746985748039345677748242309854210746050623711418779541821530464749835819412673987675591655439460770629145711964776865421676604298316526

24386837205668069376

Ruby will increase the precision of the number, or decrease it as needed:

x = 1000000puts "#{x} "+x.class.to_s => 1000000 Fixnumx = x * xputs "#{x} "+x.class.to_s => 1000000000000 Bignumx = x / 1000000puts "#{x} "+x.class.to_s => 1000000 Fixnum

16. Parallel Assignment

You can swap the values in variables without the use of a temp variable. Remember yourfirst programming class: Swap the values in "i" and "j"? You had to use a "t" variable tostore one of the values first. Not needed in Ruby.

i = 0j = 1puts "i = #{i}, j=#{j}"i,j = j,iputs "i = #{i}, j=#{j}"

Produces:

i = 0, j=1i = 1, j=0

17. Collections1. Arrays

1. An array of known objects can be created by enclosing them in squarebrackets.

2. nums = [1, 2.0, "three"]3. puts nums[2] => three

Ruby arrays, like all right-thinking collections, are zero based.

4. You can use negative indexes to start from the end of the array5. nums = [1, 2.0, "three", "four"]6. puts nums[-1] => four

Using "-1" is so much more concise than "nums[nums.length()-1]".

7. You can even use the handy "first" and "last" methods.8. [1,2,3].last => 39. [1,2,3].first => 1

10. length

To get the count, or size, of an array, use the "length" method.


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mystuff = ["tivo","nokia", "ipaq"] # make a string arrayputs mystuff.length => 3

11. %w shortcut

Since many arrays are composed of single words and all those commas andquote marks are troublesome, Ruby provides a handy shortcut, %w:

mystuff = %w{tivo nokia ipaq} # make a string array

12. inspect

To look at contents of an object use the "inspect" method. Even moreconvenient is to use "p" as a shorthand for "puts obj.inspect"

myarray = [1,2,5,7,11]puts myarrayputs myarray.inspectp myarray

Produces:

125711[1, 2, 5, 7, 11][1, 2, 5, 7, 11]

13. Arrays can act like queues and sets14. # & is the intersection operator15. puts [1,2,3] & [3,4,5] # prints 316.17. # + is the addition operator18. puts [1,2,3]+ [3,4,5] # prints 1,2,3,3,4,519.20. # - removes items from the first array that appear in

the second21. puts [1,2,3] - [3,4,5] # prints 1,222.23. # pop returns the last element and removes it from the

array24. alpha = ["a","b","c","d","e","f"]25. puts "pop="+alpha.pop # pop=f26. puts alpha.inspect # ["a", "b", "c", "d", "e"]27.28. # push appends elements to the end of an array29. alpha = ["a","b","c"]30. alpha.push("x","y","z")31. puts alpha.inspect # ["a", "b", "c", "x", "y",

"z"]32.33. # shift returns the first element and removes it from

the array34. alpha = ["a","b","c","d","e","f"]35. puts "shift="+alpha.shift # shift=a36. puts alpha.inspect # ["b", "c", "d", "e", "f"]37.38. # unshift appends elements to the beginning of an array39. alpha = ["a","b","c"]


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40. alpha.unshift("x","y","z")41. puts alpha.inspect # ["x", "y", "z", "a", "b",

"c"]

2. Hashes

This type of collection is also called a dictionary or an associative array.

1. Simple hash of cars and their makers2. cars = {3. 'altima' => 'nissan',4. 'camry' => 'toyota',5. 'rx7' => 'mazda'6. }7. puts cars['rx7'] => mazda

8. You can create a hash and fill it dynamically9. dict = {} # create a new dictionary10. dict['H'] = 'Hydrogen' #associate the key 'H' to the

value 'Hydrogen'11. dict['He'] = 'Helium'12. dict['Li'] = 'Lithium'

13. p dict['H'] # prints "Hydrogen"14. p dict.length # prints 315. p dict.values # prints ["Lithium", "Helium",

"Hydrogen"]16. p dict.keys # prints ["Li", "He", "H"]17. p dict # prints {"Li"=>"Lithium",

"He"=>"Helium", "H"=>"Hydrogen"}

18. Hash[]

You can also create Hashes with square brackets by prefixing with "Hash":

toppings =

Hash["pancakes","syrup","Pizza","Pepper","Cereal","Sugar"]puts toppings.inspect

Produces:

{"Pizza"=>"Pepper", "Cereal"=>"Sugar", "pancakes"=>"syrup"}

19. each

The "each" method is a wonderful way to iterate over the keys

toppings =Hash["pancakes","syrup","Pizza","Pepper","Cereal","Sugar"]toppings.each{|key, value| puts "#{key} points to #{value}"}

Produces:

Pizza points to PepperCereal points to Sugarpancakes points to syrup

20. select

The "select" method populates a new array with members which meet acriteria


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salaries =Hash["bob",10.9,"larry",7.5,"jimmy",6.0,"jerry",6.5]salaries.inspectmySalaryArray = salaries.select{|name,salary| salary > 7.0}puts mySalaryArray.inspect => [["larry", 7.5], ["bob",10.9]]

3. Ranges

Ranges are composed of expr..expr or expr...expr. Two dots includes the lastelement, three dots excludes it.

('a'..'g').each{ |letter| puts letter }

Produces:

abc

defg(1...3).each{ |num| puts num }

Produces only two numbers since "..." does not include the last element.:

12

18. Control Statements

1. if In an "if" statement anything but the two special values, "false" and "nil" areconsidered true. Even zero is true for all you C/C++ programmers.

2. income = 30000.003. if income < 100004. rate = 0.025. elsif income < 300006. rate = 0.287. else8. rate = 0.59. end10. puts rate

11. case12. grade = 1013. school = case grade14. when 0..515. "elementary"16. when 6..817. "middle school"18. when 9..1219. "high school"20. else21. "college"22. end23. puts "grade #{grade} is in #{school}"

24. for

25. for i in 1..426. puts "hi #{i}"27. end


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The ranges can of course have variables

top = 6for i in 1..topputs "hi #{i}"end

28. exit29. lines = IO.readlines("data.txt")30. if lines.length < 10031. exit 232. end33. puts lines.length

34. loop

iterates over code until a "break" or eternity ends

i=0loop do

break if i > 5puts ii += 1

end

19. Statement modifiers

These are just syntatic sugar.

1. if

The "if" clause may be placed at the end of a statement

balance = -10.0puts "Bankrupt" if balance < 0.0

2. unless

"unless" is placed at the end of a statement

balance = -10.0puts "Bankrupt" unless balance > 0.0

3. while

"while" may be after its block

f=2puts f=f+2 while f < 10=>4=>6=>8=>10

20. Iterators

1. while2. i = 03. while i < 54. i = i+1


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5. puts i6. end

7. "times"8. n = 109. n.times { |i| print i}

Produces:

0123456789

10. "each"11. animals = %w(lions tigers bears)12. animals.each{|kind| print kind}13. lionstigersbears

14. "each" with ranges15. ('m'..'z').each {|ch| print ch}16. mnopqrstuvwxyz

17. "upto"18. n=0 ; max=7

19. n.upto(max) {|num| print num}20. 01234567

21. You gotta have class.1. Classes

Class definitions start with "class" and end with "end". Remember that class namesstart with a capital letter. Notice the syntax is "object.new" for creating an objectand that the "initialize" method contains code normally found in the constructor.Here's a small example:

class Persondef initialize(fname, lname)

@fname = [email protected] = lnameend

endperson = Person.new("Augustus","Bondi")print person

Produces:

#

which is true, but not helpful.

2. The "ToString" method, to_s3. class Person4. def initialize(fname, lname)5. @fname = fname6. @lname = lname7. end8. def to_s9. "Person: #@fname #@lname"10. end11. end12. person = Person.new("Augustus","Bondi")

13. print person

Produces:


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Person: Augustus Bondi

14. Subclassing

In Ruby subclassing is done with the "


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endemployee = Employee.new("Augustus","Bondi","CFO")puts employeeputs employee.fnameemployee.position = "CEO"puts employee

15. Virtual Attributes16. class Employee < Person17. def initialize(fname, lname, position)18. super(fname,lname)19. @position = position20. end21. def to_s22. super + ", #@position"23. end24. attr_writer :position25. def etype26. if @position == "CEO" || @position == "CFO"27. "executive"28. else

29. "staff"30. end31. end32. end33. employee = Employee.new("Augustus","Bondi","CFO")34. employee.position = "CEO"35. puts employee.etype => executive36. employee.position = "Engineer"37. puts employee.etype => staff

22. Regular Expressions

Strings can be compared to a regular expression with "=~". Regular expressions are

surrounded by "//" or "%r{}". Anything but the two special values, "false" and "nil" areconsidered true.

Expression Result Description

/a/ =~ "All Gaul is divided into threeparts"

5 finds the first "a" at position 5

%r{a} =~ "All Gaul is divided into threeparts"

5 same thing with alternate syntax

/ree/ =~ "All Gaul is divided into three

parts"

27 finds "ree" at position 27

/^a/ =~ "All Gaul is divided into threeparts"

nil"^" implies at the beginning of a line. nilis false.

/^A/ =~ "All Gaul is divided into threeparts"

0 case-sensitive, remember that "0" is true

/s$/ =~ "All Gaul is divided into threeparts"

35 "$" implies at the end of a line

/p.r/ =~ "All Gaul is divided into threeparts"

31 "." matches any character

23. Blocks

And now to one of the coolest things about Ruby - blocks. Blocks are nameless chunks ofcode that may be passed as an argument to a function.


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1. Simple Example2. def whereisit3. yield4. yield5. yield6. end7. whereisit {puts "where is the money?"}

Produces:

where is the money?where is the money?where is the money?

In the above example '{puts "where is the money?"}' is called a block. That chunkof code is passed to the method "whereisit" and executed each time the "yield"statement is executed. You can think of the "yield" being replaced by the block ofcode.

8. Blocks can take arguments

Here the method "cubes" takes the max value.

def cubes(max)i=1while i < max

yield i**3i += 1

endendcubes(8) { |x| print x, ", "} => 1, 8, 27, 64, 125, 216, 343,

sum = 0cubes(8) { |y| sum += y}print "\nsum=",sum => sum=784product = 1cubes(8) { |z| product *= z}print "\nproduct=",product => product=128024064000

Think of the "yield i**3" in the function cubes as being replaced with the block, '|x|print x, ", "'. The value following the "yield" is passed as the value "x" to the block.

9. Multiple arguments may be passed to blocks.10. def employee(empId)

11. #next 2 lines simulated from calling a database on theempId

12. lastname = "Croton"13. firstname = "Milo"14. yield lastname,firstname #multiple arguments sent to

block15. end16. employee(4) { |last,first| print "employee ",": ",first, "

",last}

Produces:

employee : Milo Croton

17. Local variables can be shared with a block


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Even though rate is a local variable, it is used inside the block.

def tip(mealCost)yield mealCost

endrate = 0.15mytip = tip(10.0) { |cost| cost * rate }print "tip should be: ",mytip

Produces:

tip should be: 1.5

18. Blocks are built in to many objects in ruby1. each

iterates through each item of a collection

[1,2,3,4].each{|x| print x**2," "}

Produces:

1 4 9 16

2. detect

returns the first item matching a logical expression

numbers = [1,3,5,8,10,14]firstDoubleDigit = numbers.detect {|x| x > 9}

print firstDoubleDigit => 10

3. select

returns all items matching a logical expression

numbers = [1,2,3,4,5,6,7];evens = numbers.select{|x| x % 2 == 0}p evens => [2, 4, 6]

4. collect

returns an array created by doing the operation on each element.

[1,2,3,4].collect{|x| x**3} => [1, 8, 27, 64]["the","quick","brown", "lox"].collect{|x| x.upcase} =>["THE", "QUICK", "BROWN", "LOX"]

5. inject

"inject" is the "fold"or "reducer" function in Ruby. "inject" loops over anenumerable and performs an operation on each object and returns a singlevalue.

primes = [1,3,5,7,11,13];#using "inject" to sum. We pass in "0" as the initial value
http://en.wikipedia.org/wiki/Fold_(higher-order_function)http://en.wikipedia.org/wiki/Fold_(higher-order_function)http://en.wikipedia.org/wiki/Fold_(higher-order_function)


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sum = primes.inject(0){|cummulative,prime|cummulative+prime}puts sum =>40#we pass in no initial value, so inject uses the firstelementproduct = primes.inject{|cummulative,prime|cummulative*prime}puts product =>15015

#just for fun let's sum all the numbers from 1 to, oh, say amillionsum = (1..1000000).inject(0){|cummulative,n| cummulative+n}puts sum =>500000500000#you can do interesting things like build hasheshash = primes.inject({}) { |s,e| s.merge( { e.to_s => e } )}p hash # => {"11"=>11, "7"=>7, "13"=>13, "1"=>1, "3"=>3,"5"=>5}

24. File I/O1. Read an entire file into a string2. file = File.new( "t1.php" )3. mytext = file.read

4. Read an entire file into an array of lines5. lines = IO.readlines("data.txt")6. puts lines[0] #prints the first line

7. Read a file line by line8. file = File.open("res.txt")9. while line = file.gets10. puts line11. end

Or you can use the IO class

IO.foreach("data.txt") { |line| puts line }

12. Read a file line by line

You should ensure the file is closed as well.

beginfile = File.open("res.txt")

while line = file.getsputs line

endensure

file.closeend

13. Read only a few bytes at a time

The following snippet of code reads a file which may have no line breaks andchops it into 80 character lines

require 'readbytes'file = File.new( "C:/installs/myapp_log.xml" )while bytes = file.readbytes(80)

print bytes+"\r\n"endfile.close


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14. Reads a large XML file and inserts line breaks

Uses TruncatedDataError to grab the last few slacker bytes from the end.

# reads an xml file without line breaks and puts a line breakbefore each '


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program ending

34. converting between strings and ints

Use the to_i and to_s methods

"3".to_i #return an integer

3.to_s # returns a string

35. Using XML Dom Parser

REXML goes standard with Ruby 1.8. Sample to print all "div" elements whose "class"attribute is set to "entry".

require "rexml/document"file = File.new( "t0.xml" )doc = REXML::Document.new filedoc.elements.each("//div[@class='entry']") { |element| puts element }

36. Run a few lines directly from the command line with the "-e" option37. c:\home\mfincher>ruby -e 'sleep 2'38. c:\home\mfincher>ruby -e 'puts 3*4'39. 1240. c:\home\mfincher>ruby -e 'puts 3*4; puts 4*4'41. 1242. 16

43. Editing files in place

Ruby offers a simple way to make a string substitution in many files all at once with asingle line of code. The "-p" option loops over the files, the "-i" is the backup extension.

With this command we are changing all the documentation from version 1.5 to 1.6, but theoriginal files are renamed to ".bak".

C:\home\mfincher\ruby>more v2.txtRegarding version 1.5 .......version 1.5 is easy to install

C:\home\mfincher\ruby>ruby -pi.bak -e "gsub(/1.5/,'1.6')" v*.txt

C:\home\mfincher\ruby>more v2.txtRegarding version 1.6 .......

version 1.6 is easy to install

C:\home\mfincher\ruby>more v2.txt.bakRegarding version 1.5 .......version 1.5 is easy to install

44. Example of printing duplicate lines in sorted file.45. #prints duplicate lines in sorted files in the file passed in as first

arg46. file = File.open(ARGV[0])47. lastLine = ""48. counter = 049. while line = file.gets50. counter += 151. if lastLine == line52. puts "#{counter-1}: #{line}#{counter}: #{line}\r\n"


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53. end54. lastLine = line55. end56. puts "done. Processed #{counter} lines"

57. Ruby has its own interpreted shell, irb.58. C:\home\mfincher>irb59. irb(main):001:0> puts "Hello World"60. Hello World

61. => nil62. irb(main):002:0> a=163. => 164. irb(main):003:0> a*265. => 266. irb(main):004:0>

67. ruby can take input from stdin68. echo 'puts "hello"' | ruby

69. to pass a string on the url it needs to be "escape"'d first.70. require 'uri'71. ...72. URI.escape("some string...")

73. Example to remove "funny" characters from a filename

Example of iterating over the filenames in a directory, using regular expressionsubstitution in strings, and renaming files.

#replaces any "funny" characters in a filename in the current directorywith an underscore#if the new file name already exists, this skips it.Dir.foreach(".") { |f|print "testing \"#{f}\""if f =~ /[^\w\-\.]/ #filename contains something other than letters,

numbers, _,-, or .puts "\r\n name with funny characters: #{f}"newName = f.gsub(/[^\w\.\-]/,"_") # \w is any word character,

letter,num or _if File.exist?(newName)

puts " File #{newName} already exists. Not renaming."else

puts " renaming #{f} to #{newName}"File.rename(f,newName)

endelseputs " it's ok."

end}

74. Looping over list of arguments75. ARGV.each {|f|76. puts f77. counter = 078. file = File.open(f,"r")79. ftmp = f+".tmp"80. tmp = File.open(ftmp,"w")81. while line = file.gets82. if line =~ /pid="2"/83. counter += 184. line = line.gsub(/pid="2"/,"pid=\"#{f}:#{counter}\"")

85. puts line86. end87. tmp.print line88. end89. file.close


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90. tmp.close91. puts "renaming #{ftmp} to #{f}"92. File.rename(ftmp,f)93. }94.

95. Miscellanous Commands

Interesting string functions

96. DateTime97. puts DateTime.now #prints 2006-11-25T14:26:15-060098. puts Date.today #prints 2006-11-2599. puts Time.now #prints Sat Nov 25 14:29:57 Central Standard Time

2006

100. Using 'require'

require will let your access code from other files. 'require' looks in directories specified in$LOAD_PATH to find the files. The environmental variable RUBYLIB can be used toload paths into $LOAD_PATH.

C:\home\mfincher\ruby>irbirb(main):001:0> p $LOAD_PATH["c:/opt/ruby/lib/ruby/site_ruby/1.8","c:/opt/ruby/lib/ruby/site_ruby/1.8/i386-msvcrt","c:/opt/ruby/lib/ruby/site_ruby", "c:/opt/ruby/lib/ruby/1.8","c:/opt/ruby/lib/ruby/1.8/i386-mswin32", "."]=> nil

You can put a library like 'startClicker.rb' in any of those directories and ruby will find it.

require 'startClicker'

101. BuiltIn Command Interpreter

With the "eval" method you can create your own interpreter language and run it duringexecution.

irb(main):007:0> a = 6=> 6irb(main):008:0> b = 7=> 7irb(main):009:0> eval "c=a+b"=> 13

irb(main):010:0> puts c13

102. Introspection with ObjectSpace

You can find all the objects in your program of a particular type usingObjectSpace.each_object.

class Persondef initialize(name,age)@name = [email protected] = age

endattr_reader :name

endp = Person.new("Alfred",34)


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p2 = Person.new("Janie",31)ObjectSpace.each_object(Person) {|s|

puts s.name}

Produces:

JanieAlfred

103. Testing

Ruby comes right out of the box with a testing framework. Here's a quick example:

require 'test/unit'

class TestMe < Test::Unit::TestCase

def test_add

s = 1 + 1assert_equal(2, s)end

end

104. Read a URL and print the web page to the screen.

This will get a particular page and print to the screen:

require 'open-uri'open('http://www.fincher.org/Misc/Pennies'){ |f| print f.read }

This will read a file of urls and print all to the screen:

#Reads first argument as file containing urls and prints them#usage: ruby wget.rb wget.txtrequire 'open-uri'IO.foreach(ARGV[0]) { |line| open(line){ |f| print f.read } }

105. Example of drawing a line on a canvas in Tk

Tk is a graphical subsystem used in languages like Perl and Tcl.

#draws a single line on a big canvasrequire 'tk'include Math

TkRoot.new do |root|title "Solo Line"geometry "600x600"canvas2 = TkCanvas.new(root) do |canvas|

width 600height 600pack('side' => 'top', 'fill'=>'both', 'expand'=>'yes')points = []

end

TkcLine.new(canvas2, 0,0,100,100)endTk.mainloop


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106. irb - interactive ruby

Ruby comes with an REPL (Read Eval Print Loop) utility to let you try ruby interactively.("inf-ruby.el" provides an internal shell in emacs for irb).

C:>irbirb(main):001:0> puts "hello"

puts "hello"hellonilirb(main):002:0> Object.methodsObject.methods["send", "name", "class_eval", "object_id", "new", "singleton_methods","__send__", "private_method_defined?", "equal?", "taint", "frozen?","instance_variable_get", "constants", "kind_of?", "to_a","instance_eval", "require", "ancestors", "const_missing", "type","instance_methods", "protected_methods", "extend","protected_method_defined?", "eql?", "public_class_method", "const_get","instance_variable_set", "hash", "is_a?", "autoload", "to_s","class_variables", "class", "tainted?", "private_methods",

"public_instance_methods", "instance_method", "untaint","included_modules", "private_class_method", "const_set", "id", "", "===", "clone","public_methods", "protected_instance_methods", "require_gem", ">=","respond_to?", "display", "freeze", "


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Thanks for visiting

5. How to Freeze a version

Since your hosting company may upgrade the rails version you need to "freeze" thecurrent version. The following copies all the 1.2.6 libraries from the shared

directory to your own private one.

rake rails:freeze:edge TAG=rel_1-2-6

6. Active record notes1. Find all records meeting a criteria2. def self.suitable_jokes(sort_key)3. if sort_key == "Newest"4. find(:all,5. :conditions => "suitable = \"1\"",6. :order => "entry_date DESC"7. )

8. elsif sort_key == "Worst"9. find(:all,10. :conditions => "suitable = \"1\"",11. :order => "entry_date ASC"12. )13. else14. find(:all,15. :conditions => "suitable = \"1\"",16. :order => "current_rating DESC"17. )18. end19. end

The first argument to find can also be ":first" or ":last".

20. Find the count of records meeting a criteria21. def self.waiting_jokes()22. count("suitable = \"0\"")23. end24. def self.total()25. count("suitable = \"1\"")26. end

Find the total number of items

count = Joke.count

Find the total number of items meeting a criteria

count = Joke.count(["suitable = \"1\""])

27. Pagination

The ":limit" and ":offset" options allow easy pagination.

To return the fifth page of items use the following:

find(:all,:conditions => "suitable = \"1\"",:order => "current_rating DESC",


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:limit => 10,:offset => 40

)

28. Use raw SQL and return two values29. def getAverageRatingAndCount30. record = Rating.find_by_sql(["select count(*) as

count,avg(rating) as average from ratings WHERE joke_id

= ?",id]);31. return record[0].average.to_f ,

record[0].count.to_i32. end

33. The "create" method in ActiveRecord will do "new" and "save" operationssimultanously.

34. mydog = Dog.create(35. :name => "Fido"36. :breed => "Collie"37. )

7. Watir

Watir is a GUI testing tool written in Ruby. Here is a script to open Google andsearch for pictures of kittens.

require "watir"ie = Watir::IE.new #create an object to drive the browserie.goto "http://www.google.com/"ie.url == "http://www.google.com/"ie.link(:text, "Images").flash #flash the item text "Images"ie.link(:text, "Images").click #click on the link to the imagessearch pageie.text.include? "The most comprehensive image search on the web"#test to make sure it worked

searchTerm = "kittens" #set a variable to hold our search termie.text_field(:name, "q").set(searchTerm) # q is the name of thesearch fieldie.button(:name, "btnG").click # "btnG" is the name of the googlebuttonif ie.contains_text(searchTerm)puts "Test Passed. Found the test string: #{searchTerm}. Actual

Results match Expected Results."else

puts "Test Failed! Could not find: #{searchTerm}"end

8. Selecting a JavaScript popup box

stolen from http://wiki.openqa.org/display/WTR/FAQ

#Watir script to show clicking a JavaScript popup boxrequire "watir"require 'watir\contrib\enabled_popup'require 'startClicker'require 'net/http'require 'net/https'

$ie = Watir::IE.new #create an object to drive the browser$ie.goto "http://mydomain.com/ListGroups.aspx"

if $ie.contains_text("Log In")$ie.text_field(:name, "Login1$UserName").set("fincherm")$ie.text_field(:name, "Login1$Password").set("mitch")$ie.button(:name, "Login1$LoginButton").click

end


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$ie.link(:text, "Baseline").click$ie.link(:text, "MoonManC").clickdef setDdlPriority(priority)

ddlPriority = $ie.select_list( :name , /ddlPriority/)puts ddlPriorityddlPriority.select(priority)puts ddlPriority$ie.button(:name, "ctl00$btnSave").click_no_wait

startClicker( "OK", 4 , "User Input" )sleep 1

endsetDdlPriority("2")setDdlPriority("9")

startClicker.rb:

#method startClicker from http://wiki.openqa.org/display/WTR/FAQdef startClicker( button , waitTime= 9, user_input=nil )# get a handle if one existshwnd = $ie.enabled_popup(waitTime)if (hwnd) # yes there is a popupw = WinClicker.newif ( user_input )w.setTextValueForFileNameField( hwnd, "#{user_input}" )

end# I put this in to see the text being input it is not

necessary to worksleep 3# "OK" or whatever the name on the button isw.clickWindowsButton_hwnd( hwnd, "#{button}" )## this is just cleanupw=nil

endend

9. How to use Watir with NUnit

Here is an example of connecting it to NUnit.

using System;using System.Diagnostics;using System.Text.RegularExpressions;using NUnit.Framework;

namespace SurveyDirector.Test.Watir{

/// /// from

http://www.hanselman.com/blog/IntegratingRubyAndWatirWithNUnit.aspx

/// with small hacks from Liz Buenker/// public class WatirAssert{

public static void TestPassed(string rubyFileName, stringdirectoryPath)

{string output = String.Empty;using (Process p = new Process()){

p.StartInfo.UseShellExecute = false;p.StartInfo.RedirectStandardOutput = true;
http://www.hanselman.com/blog/IntegratingRubyAndWatirWithNUnit.aspxhttp://www.hanselman.com/blog/IntegratingRubyAndWatirWithNUnit.aspxhttp://www.hanselman.com/blog/IntegratingRubyAndWatirWithNUnit.aspxhttp://www.hanselman.com/blog/IntegratingRubyAndWatirWithNUnit.aspx


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p.StartInfo.FileName = "ruby.exe";p.StartInfo.Arguments = rubyFileName + " -b";p.StartInfo.WorkingDirectory = directoryPath;p.Start();output = p.StandardOutput.ReadToEnd();p.WaitForExit();

}Console.Write(output);

Trace.Write(output);Regex reg = new Regex(@"(?\d+) tests, (?

\d+) assertions, (?\d+) failures, (?\d+) errors", RegexOptions.Compiled);

Match m = reg.Match(output);try{

int tests = int.Parse(m.Groups["tests"].Value);int assertions =

int.Parse(m.Groups["assertions"].Value);int failures =

int.Parse(m.Groups["failures"].Value);int errors = int.Parse(m.Groups["errors"].Value);

if (tests > 0 && failures > 0){Assert.Fail(String.Format("WatirAssert:

Failures {0}", failures));}else if (errors > 0){

Assert.Fail(String.Format("WatirAssert: Errors{0}", errors));

}}catch (Exception e){

Assert.Fail("WatirAssert EXCEPTION: " +e.ToString());}

}}

}

The above code would be used by something like this:

using System;using NUnit.Framework;

namespace SurveyDirector.Test.Watir

{[TestFixture]public class WatirTest{

private static readonly string testDir =Utilities.Properties.baseDir + "\\Test\\Watir";

public WatirTest() { }[Test]public void Sd01Test(){

WatirAssert.TestPassed("sd01_test.rb",testDir);}[Test]

public void Sd02Test(){

WatirAssert.TestPassed("sd02_test.rb",testDir);}


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}}

109. Ruby Quotes:

"Ruby is a language for clever people." -Matz"Ruby is the perlification of Lisp." -Matz"Type Declarations are the Maginot line of programming." -Mitch Fincher

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