This document summarizes a presentation comparing Groovy and JRuby. Groovy dynamicizes the Java platform by adding dynamic language features to Java, while JRuby brings Ruby to the Java platform. Both languages add objects to support collections and other features, but implement meta-programming and other techniques differently. Groovy encapsulates and extends existing Java frameworks, while Ruby tends to build abstraction layers using meta-programming and DSLs. Both languages have advantages and disadvantages for unparalleled Java integration versus being cross-platform.

1. ThoughtWorks
comparing
groovy & jruby *
* please check all knives, guns, pitchforks, and torches at the door
NEAL FORD software architect / meme wrangler
ThoughtWorks
nford@thoughtworks.com
3003 Summit Boulevard, Atlanta, GA 30319
www.nealford.com
www.thoughtworks.com
blog: memeagora.blogspot.com
twitter: neal4d

2. housekeeping
ask questions at the end
(insane amount of material!)
download slides from
nealford.com
download samples from github.com/nealford

3. agenda:
syntax
closures
eigenclass approaches
meta-programming
framework approach

4. geek fu test:

5. Groovy dynamicizes JRuby brings Ruby to
the Java platform
TM
the Java platform
TM

7. differences & observations

8. syntax

9. sigils

10. this.name
vs
@name

13. auto-encapsulation?

16. Perl !!!!!!!!!

17. Ruby has some Perl-isms...
...with significant differences

18. closures

23. passing closures

24. auto-blocks

25. passing closures

26. everything except...
in Java™, everything is an object...
...except primitives and nulls
in Groovy, everything is an object...
except null
in JRuby, everything is an object.

27. null is null
?. handles protected
reference
person?.address?.street

28. nil is an instance of
NilClass

30. switch/case statement

33. === isCase()

34. “spread” operator

35. “elvis” operator

36. side effects of
encapsulating
Java™

37. things added to Object

38. supporting collections

39. really? really!

40. JRuby additions
JRuby adds artifacts to “Rubify” Java™
ArrayList
Fixnum
...but doesn’t add collection stuff to Object

41. Groovy is (kind of)
optionally typed

43. search exists on Stack
but not on ArrayList
or List!

44. interfaces & mixins

45. Groovy & interfaces
allows you to interact with Java™ interfaces
can wrap proxies around them if needed
“fake out” interfaces via closures using as

47. be careful when implementing with a map:
NullPointerException if you forget a method

48. Ruby has no interfaces
mixin
first appeared in symbolic logic’s flavors system
named after ice cream mix-ins
not a form of specialization
a way to collect functionality

50. comparisons

51. comparisons

54. comparisons

55. violating handshakes

56. mixins in Groovy,
interfaces in JRuby

58. interfaces in JRuby?

60. meta-programming

61. mostly parity (functionally)
very different implementations

62. executable declarations
much of Ruby’s infrastructure is meta-
programming
meta-programming methods:
attr_reader, attr_writer,
attr_accessor
include
private, protected, public

63. AST transformations

64. implementation

66. optional inclusion

67. conditional method

68. attributes

69. hook methods

70. sticky attributes
private, protected, public

71. eigenclass

72. adding methods via
proxies

74. Groovy’s eigenclass

75. framework
approach

76. encapsulate
& extend

77. Groovy & Grails
leverage the existing industrial strength Java™
stack
encapsulate best-of-breed frameworks
use Groovy to simplify and humanize them
encapsulate, then build up

79. abstraction
layers
via
meta || dsl

80. Ruby
tends to build things as abstraction layers atop
Ruby using meta-programming & dsl techniques
Ruby on Rails = software factories + dsl’s
Ruby language is always 1 abstraction layer
down
lightweight abstraction layers

81. case study: builders

82. GroovyObjectSupport
BuilderSupport
MarkupBuilder

84. builder

85. builder works via
method_missing
but what about this?

87. the problem:
how do you inherit from object...
...with inheriting from object?

88. Jim Weirich’s
1.8 BlankSlate
Object BasicObject
BlankSlate
Builder
Recorder Builder
Recorder
Recorder
1.9
BasicObject

90. different philosophies
Groovy encapsulates and builds up
Ruby either builds
abstractions with dsl’s
via meta-programming

91. summary

94. the good
unparalleled Java™ integration
willing to evolve the language
the real JDK™ 2.0!
building up from best-of-breed

95. the bad
fast changing at the core
single runtime platform
never spread out of the Java™ community
framework approach?

96. def name
public String getName()
public void setName(String name)

98. the good
well established (older than Java™)
virtually effortless meta-programming
futuristic framework approach
truly cross platform, for the new definition of
platform
interpreted, then jit-ted

99. the bad
some impedance mismatch with Java™ (smaller
all the time)
yet another language to learn
unfamiliar frameworks
you have to switch to a new community
you have to learn to think like a Ruby-ist

101. ThoughtWorks
?’s
please fill out the session evaluations
samples at github.com/nealford
NEAL FORD software architect / meme wrangler
ThoughtWorks
nford@thoughtworks.com
This work is licensed under the Creative Commons 3003 Summit Boulevard, Atlanta, GA 30319
www.nealford.com
Attribution-Share Alike 3.0 License. www.thoughtworks.com
blog: memeagora.blogspot.com
http://creativecommons.org/licenses/by-sa/3.0/us/ twitter: neal4d

102. ThoughtWorks
resources
Cow in the Road photo by Sophia Huda, from
Flickr, under a Creative Commons license
groovy web site
http://groovy.codehaus.org
jruby site
http://jruby.codehaus.org
ola bini’s blog
http://olabini.blogspot.com/
charles nutter’s blog
http://headius.blogspot.com/

103. ThoughtWorks
resources
jeff brown’s blog
http://javajeff.blogspot.com/
graeme rocher’s blog
http://graemerocher.blogspot.com/
aboutGroovy
http://aboutGroovy.com
venkat subramaniam’s blog
http://www.agiledeveloper.com/blog/