Hidden treasures of Ruby

HIDDEN TREASURES
of
RUBY

@MrJaba - iprug - 6th Dec 2011

Whistlestop tour through the lesser
known/obscure features of Ruby

Ruby has a
HUGE
standard library

Have you heard of?
Struct

OpenStruct

OptionParser

Abbrev

Benchmark

Find

English

Did you know about?
String#squeeze

String#count

String#tr

Kernel#Array

Kernel#trace_var

STRING
#squeeze

“Uh oh the cat sat on the keeeeeeeeeee”.squeeze
=>
“Uh oh the cat sat on the ke”

“oh craaaapppp my aaappp keys are bloody
broken”.squeeze(“ap”)
=>
“oh crap my ap keys are bloody broken”

STRING
#count

“FINISHED FILES ARE THE RE-
SULT OF YEARS OF SCIENTIF-
IC STUDY COMBINED WITH
THE EXPERIENCE OF YEARS.”

How many F’s are there?

STRING
#count

“FINISHED FILES ARE THE RE-
SULT OF YEARS OF SCIENTIF-
IC STUDY COMBINED WITH
THE EXPERIENCE OF YEARS.”.count(“F”)

=>
6

STRING
#count

“how many woods would a wood chuck chuck if a
wood chuck could chuck wood?”.count(“a-z”, “^u”)

=>
52

“DYTSMH”
.tr(“DYTSMH”, “STRING”)

“STRING”
.tr(“R-T”, “F”)

“FFFING”

KERNEL
#Array

yesthat’sacapitalletter

Array(1..3) + Array(args[:thing])
=
[1,2,3, “Thing”]
thing.to_a
=
NoMethodError: undeﬁned method `to_a' for
thing:String

KERNEL
#at_exit

at_exit { p ObjectSpace.count_objects }
=
{:TOTAL=31479, :FREE=4687, :T_OBJECT=1442, :T_CLASS=859, :T_MODULE=32, :T_FLOAT=7,
:T_STRING=18190, :T_REGEXP=168, :T_ARRAY=3657, :T_HASH=134, :T_STRUCT=1, :T_BIGNUM=2,
:T_FILE=6, :T_DATA=1210, :T_MATCH=100, :T_COMPLEX=1, :T_NODE=949, :T_ICLASS=34}

at_exit {
loop do
p “unkillable code!”
end }

KERNEL
#set_trace_func
class Cheese
def eat
p “om nom nom”
end
end

set_trace_func proc {|event, ﬁle, line, id, binding, classname|
p “#{event}, #{ﬁle}, #{line}, #{id}, #{binding}, #{classname}”
}

=
c-return, cheese.rb, 9, set_trace_func, #Binding:0x007fe11b84e488, Kernel
line, cheese.rb, 11, , #Binding:0x007fe11b84e1e0,
c-call, cheese.rb, 11, new, #Binding:0x007fe11b84dfb0, Class
c-call, cheese.rb, 11, initialize, #Binding:0x007fe11b84dc90, BasicObject
c-return, cheese.rb, 11, initialize, #Binding:0x007fe11b84da38, BasicObject
c-return, cheese.rb, 11, new, #Binding:0x007fe11b84d808, Class
line, cheese.rb, 12, , #Binding:0x007fe11b84d5d8,
call, cheese.rb, 2, eat, #Binding:0x007fe11b84d3a8, Cheese
line, cheese.rb, 3, eat, #Binding:0x007fe11b84d150, Cheese
c-call, cheese.rb, 3, p, #Binding:0x007fe11b84cef8, Kernel
c-call, cheese.rb, 3, inspect, #Binding:0x007fe11b84ccc8, String
c-return, cheese.rb, 3, inspect, #Binding:0x007fe11b84ca48, String
om nom nom
c-return, cheese.rb, 3, p, #Binding:0x007fe11b84c7f0, Kernel
return, cheese.rb, 4, eat, #Binding:0x007fe11b84c5c0, Cheese

Struct

Point = Struct.new :x, :y do
def distance(point)
Math.sqrt((point.x - self.x) ** 2 +
(point.y - self.y) ** 2)
end
end

Why? Struct

Quickly define a class with a few known fields

Automatic Hash key

Mitigate risk of spelling errors on field names

OptionParser
require ‘optparse’
options = {}
parser = OptionParser.new

parser.on(-i, --ipswich, description of IP) {|val| options[:ipswich] = val }
parser.on(-r=ARG, --ruby, Mandatory Argument) {|val| options[:ruby] = val }
parser.on(-u=[ARG], --user, Optional Argument) {|val| options[:user] = val }
parser.on(-g=ARG, --group, Integer, Type cast Argument) {|val| options[:group] = val }

unmatched = parser.parse(ARGV)

puts parser.to_s

puts options are #{options.inspect}
puts unmatched are #{unmatched.inspect}

Abbrev
require ‘abbrev’

Abbrev::abbrev(['Whatever'])

{Whateve=Whatever, Whatev=Whateve
Whate=Whatever, What=Whatever,
Wha=Whatever, Wh=Whatever,
W=Whatever, Whatever=Whatever}

Thereisno“whatevs”inthere!

Benchmark
require ‘benchmark’

puts Benchmark.measure { calculate_meaning_of_life }
=
0.42 0.42 0.42 ( 4.2)

ElapsedRealTime
UserCPU Sum
SystemCPU
Benchmark.bmbm do |x|
x.report(sort!) { array.dup.sort! }
x.report(sort) { array.dup.sort }
end
=
user system total real
sort! 12.959000 0.010000 12.969000 ( 13.793000)
sort 12.007000 0.000000 12.007000 ( 12.791000)

English
require ‘English’
$ERROR_INFO $! $DEFAULT_OUTPUT $

$ERROR_POSITION $@ $DEFAULT_INPUT $

$FS $; $PID $$

$FIELD_SEPARATOR $; $PROCESS_ID $$

$OFS $, $CHILD_STATUS $?

$OUTPUT_FIELD_SEPARATOR $, $LAST_MATCH_INFO $~

$RS $/ $IGNORECASE $=

$INPUT_RECORD_SEPARATOR $/ $ARGV $*

$ORS $ $MATCH $

$OUTPUT_RECORD_SEPARATOR $ $PREMATCH $`

$INPUT_LINE_NUMBER $. $POSTMATCH $'

$NR $. $LAST_PAREN_MATCH $+

$LAST_READ_LINE $_

Find
require ‘ﬁnd’

Find.ﬁnd(“/Users/ET”) do |path|
puts path
Find.prune if path =~ /hell/
end
= Geddit?
/Users/ET/phone
/Users/ET/home

Profiler__
require ‘profiler’

Profiler__::start_profile
complicated_method_call
Profiler__::stop_profile
Profiler__::print_profile($stdout)

% cumulative self self total
time seconds seconds calls ms/call ms/call name
0.00 0.00 0.00 1 0.00 0.00 Integer#times
0.00 0.00 0.00 1 0.00 0.00 Object#complicated_method_call
0.00 0.01 0.00 1 0.00 10.00 #toplevel

RSS
require ‘rss/2.0’

response = open(http://feeds.feedburner.com/MrjabasAdventures).read
rss = RSS::Parser.parse(response, false)
rss.items.each do |item|
p item.title
end

MiniTest
require ‘minitest/autorun’
describe Cheese do
before do
@cheddar = Cheese.new(“cheddar”)
end

describe when enquiring about smelliness do
it must respond with a stink factor do
@cheddar.smelliness?.must_equal 0.9
end
end
end

Provides:
Specs Mocking Stubbing Runners Benchmarks

Thank you to
everyone involved in
Ruby!

Hidden treasures of Ruby

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