Learning Ruby

*

* splash@dei.uc.pt 31
March
2011

This presentation is based on contents from
Mr. Neighborly's Humble Little Ruby Book

March
2011

def
what
is
ruby?

'A
programming
language'

end

def
why
do
i
need
to
learn
it?

ruby
on
rails
=
'Ruby
language'
+
'Rails
framework'

read
the
slides!
unless
u
likez
jsp

end

def
what
makes
ruby
=
:special

features
=
['Object-‐oriented']

features
<<
'Interpreted'

features
<<
'Open-‐source'

#
And

features
<<
'Mixins'
#
somewhat
similar
to
multiple
inheritance

features
<<
"Native
threads"

features
<<
"Large
standard
library"

features
<<
"Centralized
package
management
through
RubyGems"

features
<<
"Built-‐in
support
for
rational
and
complex
numbers"

features
<<
"Automatic
garbage
collection"

features
<<
"Default
arguments"

features
<<
"Literal
notation
for
arrays,
hashes,
regex
and
symbols"

features
<<
"Dynamic
typing
and
Duck
typing"

features
<<
"Operator
overloading"

features
<<
"Flexible
syntax
that
serves
as
a
foundation
for
DSL"

end

Ruby originated in Japan during the mid-1990s
Created by Yukihiro ‘Matz’ Matsumoto

Basic concepts of Ruby

-‐4.abs

#
→
4

6.zero?
#
→
false

if
(a
!=
null)
{...}
unless
a.nil?
{...}

null.toString()
//
NPE

nil.to_s
#
""

Types in Ruby

puts
-‐4

puts
0x5C1

#
1473
(Hex)

puts
01411

#
777
(Octal)

puts
12_000_000
#
12000000

puts
1.5

puts
12.043e-‐04
#
0.0012043

puts
123456789101112131415

Types in Ruby

puts
-‐4.type

#
Fixnum

puts
0x5C1.type

#
Fixnum

puts
01411.type

#
Fixnum

puts
12_000_000.type

#
Fixnum

puts
1.5.type

#
Float

puts
12.043e-‐04.type

#
Float

puts
123456789101112131415.type
#
Bignum

Types in Ruby

puts
'hellotmiguel'
#
→
hellotmiguel

puts
"hellotmiguel"
#
→
hello

miguel

-  Lightweight strings

-  Escape sequences (t, n, …)
-  Expression interpolation

puts
"hello
#{'manolo
'
*3}"

myvar.to_s
#
hello
manolo
manolo
manolo

Types in Ruby

%q{Text}
#
Single
quoted

%Q{Text}
#
Double
quoted

mystring
=
<<LOREM

Donec
id
elit
non
mi
porta
gravida
at
eget
metus.

Morbi
leo
risus,
porta
ac
consectetur
ac,
vestibulum

at
eros.
Curabitur
blandit
tempus
porttitor.

Vestibulum
id
ligula
porta
felis
euismod
semper.

Etiam
porta
sem
malesuada
magna
mollis
euismod.

Maecenas
sed
diam
eget
risus
varius
blandit
sit!

LOREM

Types in Ruby

:hello

do_this
if
query
==
:get

link_to
"View
Article",
:controller
=>
"articles",
:action
=>
"show"

Types in Ruby

cookies
=
1..10

bad_cookies
=
1..5

burnt_cookies
=
1..5

puts
bad_cookies
==
cookies

#
false

puts
bad_cookies
==
burnt_cookies

#
true

puts
bad_cookies.eql?
burnt_cookies
#
true

myguess
=
2

puts
cookies
===
myguess

#
true

puts
cookies.include?
myguess
#
true

puts
cookies.include?
2.23
#
true

puts
cookies.include?
2..4
#
false

Types in Ruby

its_empty
=
[]

oh_so_empty
=
Array.new

hello
=
['ni
hao',
'bonjour',
'hi',
'howdy',
'bom
dia']

random_types
=
[13,
'napkin',
(4+8+42).to_s]

Types in Ruby

my_waiku
=
%W(he
is
nice
to
my
#{2*7}
cats)

my_waiku.to_a
#
["he",
"is",
"nice",
"to",
"my",
"14",
"cats"]

my_range
=
1..5

my_array
=
my_range.to_a
#
[1,
2,
3,
4,
5]

my_array[6]
=
7

#
[1,
2,
3,
4,
5,
nil,
7]

my_array.insert(7,
8)

#
[1,
2,
3,
4,
5,
nil,
7,
8]

my_array.insert(-‐1,
9)

#
[1,
2,
3,
4,
5,
nil,
7,
8,
9]

my_array.pop

#
[1,
2,
3,
4,
5,
nil,
7,
8]

my_array.pop
3

#
[1,
2,
3,
4,
5]

my_array.push
6,
7

#
[1,
2,
3,
4,
5,
6,
7]

my_array
<<
8
<<
9

#
[1,
2,
3,
4,
5,
6,
7,
8,
9]

Types in Ruby

roles
=
Hash.new
'Not
here!'

roles
=
{
'LA'
=>
'Gaspar',
'PM'
=>
'Tavares',
'CM'
=>
'Gaspar'
}

roles['QM']

#
→
"Not
here!"

roles.has_key?
'LA'

#
→
true

roles.has_value?
'Catré'

#
→
false

roles.empty?

roles.clear

Types in Ruby

Alternate notation when
keys are symbols

roles
=
{
:LA
=>
'Gaspar',
:PM
=>
'Tavares'
}

roles
=
{
LA:
'Gaspar',
PM:
'Tavares'
}

RUBY
1.9.2

Operators

==
!=
<
>
<=
>=
<=>

===

.eql?
Combined comparison

0
if first equals second

1
if first is greater than the second

.equal?

-‐1
if first operand is less than the second

Operators

==
!=
<
>
<=
>=
<=>

===

True if both have the
.eql?

same type and values
.equal?
1.0
==
1

#
true

1.0.eql?
1
#
false

Operators

==
!=
<
>
<=
>=
<=>

===

.eql?

True if both have
the same object id
.equal?

a
=
1

b
=
1

a.equal?
b
#
true
(why?)

Operators

==
!=
<
>
<=
>=
<=>

===

.eql?
x
?
y
:
z

.equal?
Ternary operator

Operators

&&
||
!

=
/ =
/ =
and
or
not

Methods

- The method name should be
- If it’s it should end in a

- If it it should end in an

Variables

banana

#
is
a
variable

Banana

#
is
a
constant

@banana

#
is
an
instance
variable

@@banana
#
is
a
class
variable

$banana

#
is
a
global
variable

Modules

- You shouldn’t put things in a class that don’t
really go together
- Modules are a good excuse to break that rule
without breaking it

And because…

Blocks

-  Somewhat similar to Java
anonymous inner classes

Closures

§  A closure is a combination of a and
an

RUBY
1.9.2

Flow control

if
something

puts
"It's
so
true."

elsif
another_thing

puts
"Yeah!"

else

puts
"Wrong!"

end

puts
'Hello!'
if
something

redirect_to(home_path)
unless
current_user.logged_out?

Flow control

case
http_status_code
case

when
404:
puts
"Not
found"
when
http_status_code
<
200

when
400

puts
"Informational"

when
http_status_code.between?(200,
300)

puts
"Bad
Request"

puts
"Success!"

else

else

puts
"Another
status
code"

puts
"Maybe
next
time."

end
end

Create a class with a method which prints
5 times the sentence “Hello World!”

0
class
Sample

1

def
hello

2

5.times
{
print
"Hello
World!"
}

3

end

4
end

5

6
sample
=
Sample.new

7 sample.hello

Create a method which reads a text ﬁle and
prints the number of characters, words and lines

0
lines
=
File.new('file').readlines

1
puts
"Chars=%d,
Words=%d,
Lines=%d"
%

[lines.join.size,
lines.join.split.size,

lines.size]

Use Ruby to make an HTTP GET request on

www.ruby-lang.org/en/LICENSE.txt

0
require
'net/http'

1
Net::HTTP.start('www.ruby-‐lang.org',
80)
do
|http|

2

print
http.get('/en/LICENSE.txt').body

3
end

March
2011

1  A Quick (and Hopefully Painless) Ride Through Ruby, viewed 2011/03/31, http://
mislav.uniqpath.com/poignant-guide/book/chapter-3.html

2  Using Ruby - An Introduction to Ruby for Java Programmers, viewed 2011/03/31,
http://onestepback.org/articles/usingruby/

3  Ruby Operators, viewed 2011/03/31, http://www.tutorialspoint.com/ruby/
ruby_operators.htm

4  Mr. Neighborly's Humble Little Ruby Book, viewed 2011/03/31,  
http://humblelittlerubybook.com/

5  Ruby for Java programmers, viewed 2011/03/31, http://www.softwaresummit.com/
2006/speakers/BowlerRubyForJavaProgrammers.pdf

March
2011

http://ruby.runpaint.org/ (draft of a book about Ruby 1.9)

http://humblelittlerubybook.com/ (book about Ruby 1.8)

http://mislav.uniqpath.com/poignant-guide/ (guide featuring talking foxes)

http://www.rubyist.net/~slagell/ruby/ (another guide)

March
2011

Learning Ruby

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