Doc 17 Ruby Intro

Contents

 

Reading Assignment    

Ruby    

Some Formating    

String Literals    

Defining Functions    

Naming Convention    

Arrays & Hashes    

Control Structures    

Blocks    

 

Copyright ©, All rights reserved. 2005 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA. OpenContent ( http://www.opencontent.org/opl.shtml ) license defines the copyright on this document.

 

References

 

Programming Ruby, The Pragmatic Programmers' Guide, Dave Thomas, ISBN 0-9745140-5-5

 

 

Reading Assignment

 

Programming Ruby, The Pragmatic Programmers' Guide, Dave Thomas, ISBN 0-9745140-5-5

On-line version

 

 

Chapter 22 The Ruby Language is very useful

 

 

Future Rails Reading

 

On Nov 15 I plan to start going through

Agile Web Development with Rails, Thomas & Hansson, 2005, Pragmatic Bookshelf, ISBN 0-9766940-0-X

 

Quotes

 

Dynamic types are stronger than static types, as they don't flee the field at runtime.

Brian Foote

 

Static types give me the same feeling of safety as the announcement that my seat cushion can be used as a floatation device.

Don Roberts

 

 

Ruby

 

Main web site: http://www.ruby-lang.org/en/

 

Some Ruby Aware IDEs

 

Ruby extensions to editors:

1. http://www.rubygarden.org/ruby?EditorExtensions

 

Arachno

2. http://www.ruby-ide.com/ruby/ruby_ide_and_ruby_editor.php

3. good editor & debugger,

4. Windows & Linux,

5. Commercial with 30 day free trial

 

Ruby Eclipse plugin - rdt

6. http://sourceforge.net/projects/rubyeclipse

 

 

 

Some Basic Boring Stuff

Some Formating

a = 1

b = 2; c = 'cat'

d = 1 + 2 +

    5       #no '\' needed

e = 1 + 2

    + 3     #'\' needed

 

Number literals

 

Fixnum = native machine word minus 1 bit

Float = machines double data type

 

 

String Literals

Single Quoted

'stuff' or %q/stuff/

 

Double Quoted

"stuff", %Q/stuff/ or %/stuff/

Expands \n, \t etc and #{ruby_code }

 

 

Defining Functions

def test_me

  return 1

end

 

puts test_me

puts test_me()

 

def one_arg(x)

  return x + 1

end

 

puts one_arg(1)

puts one_arg 2              #Generates warning

puts one_arg 2 + 3          #Generates warning

 

def two_args(a, b)

  return a + b

end

 

puts two_args 1, 2          #Generates warning

puts two_args(1, 2)

 

 

 

Naming Convention

 

 

 

 

 

Arrays & Hashes

 

a = [1, 'dog', 12]

a[0]

a[1] = 3

a[5] = 'what now'

puts a

 

Output

1

3

12

nil

nil

what now

 

String Array Shortcut

a = ['this', 'is', 'painful', 'to', 'type']

b = %w{ this is a shortcut for an array of strings}

 

Hashes

aHash = {

  'cat' => 'mammal',

  'ant' => 'insect',

  'dog' => 'mammal'

}

aHash['lizard'] = 'reptile'

puts aHash['dog']

 

 

Control Structures

if x > 5

  puts "Greater than 5"

elsif x < 3

  puts "Less than 3"

else

  puts "looks like 4"

end

 

while x < 10

  puts x

  x += 1

end

 

 

 

Statement Modifiers

 

grade = 102

if grade > 100

  puts "Invalid Grade"

end

 

puts "Invalid Grade" if grade > 100

 

powers = 2

while powers < 100

  powers = powers*powers

end

puts powers

 

powers = 2

powers = powers*powers while  powers < 100

 

 

 

Blocks

 

Two Block delimiters

{ puts "Hello World" }

 

do

  x = x + 1

  y = y -1

end

 

Calling a Block

def block_example

  puts "Start"

  yield

  yield

  puts "End"

end

 

block_example {puts "Hello"}

Output

Start

Hello

Hello

End

 

yield calls the block passed to the method

 

 

Second Block Example

x = 1

block_example do

  x +=1

end

puts x

 

Output

Start

End

3

 

 

 

Blocks with Arguments

def call_block

  yield(4)

end

 

call_block { |x| puts x}

 

call_block do |x|

  puts x

end

 

def call_block

  yield(4, 5)

end

 

call_block {|x , y| puts x + y}

 

call_block do |x , y|

  puts x + y

end

 

def call_block(a, b)

  yield(a, b + 1)

end

 

call_block(1,2) {|x , y| puts x + y}