Smalltalk

I'm a Rubyist. I know nothing about Smalltalk. I explored.

Transcript

1. SMALLTALK
2. Smalltalk is like Ruby’s baby daddy I should probably know something about it
3. HISTORY
4. MUSTACHIOED ALAN KAY Xerox PARC What have you done for me lately? Kids toys: Squeak, Tweak, OLPC-OMG DAN HENRY HOLMES INGALLS, JR. Xerox PARC What have you done for me lately? Squeak, Distinguished Fellow Engineer Scientist Beach Enthusiast
5. ADELE GOLDBERG Xerox PARC We don’t hear much about her! Helped develop Smalltalk-80, wrote much of the documentation, helped develop design templates (forerunners to design patterns)
7. SYNTAX
8. RESERVED KEYWORDS
9. RESERVED KEYWORDS self
10. RESERVED KEYWORDS self super
11. RESERVED KEYWORDS self super nil
12. RESERVED KEYWORDS self super nil true
13. RESERVED KEYWORDS self super nil true false
14. RESERVED KEYWORDS self super nil true false thisContext
15. CAMELCASE VARIABLES
16. camelCase VARIABLES
17. camelCase VARIABLES
18. GlobalVariable
19. GlobalVariable ClassVariable
20. GlobalVariable ClassVariable ClassName
21. “this is a comment?”
22. “yeah, it really is”
23. $a “literal character ‘a’”
24. ‘Hello’ “is a string”
25. ‘G”day’ “is G’day”
26. #Hello “that’s a symbol”
27. #{1 2 3} “literal array”
28. #{1 2 3} “literal array” “only compile time constants inside”
29. {1. 2. 1+2} “dynamic array”
30. {1. 2. 1+2} “dynamic array” “expressions separated by periods”
31. {1. 2. 1+2} “dynamic array” “expressions separated by periods” “not kidding”
32. | x y | “declare your variables”
33. x := 1 “assign 1 to x”
34. [ x + y ] “block evaluation”
35. <primitive: 1> “virtual machine primitive”
36. <primitive: 1> “virtual machine primitive” “or annotation”
37. <primitive: 1> “virtual machine primitive” “or annotation” “I don’t know what I’m talking about at this point...”
38. MESSAGES
39. 3 factorial “unary message”
40. 3 + 4 “binary message”
41. 2 raisedTo: 6 “keyword message”
42. 2 raisedTo: 6 modulo: 10 “multi-keyword message”
43. A lesson in precedence
44. 1 + 2 * 3 -> ?
45. 1 + 2 * 3 -> 9
46. All your precedence are belong to MESSAGES!
47. So it goes: 1. Parentheses 2. Unary messages 3. Binary messages 4. Keyword messages 5. Left to right
48. 1 + 2 * 3 -> 9
49. 1 + 2 * 3 -> 9 Binary Message
50. 3 * 3 -> 9 Binary Message Binary Message
51. 3 * 3 -> 9 Binary Message Binary Message
52. Simple!
53. 1 + 2 * 3 -> 9
54. 1 + (2 * 3) -> ?
55. 1 + (2 * 3) -> 7
56. Transcript show: ‘hello’. Transcript cr
57. Transcript show: ‘hello’. Transcript cr
58. Transcript show: ‘hello’. Transcript cr
59. Transcript show: ‘hello’. Transcript cr “dot (.) is an expression separator”
60. Transcript show: ‘hello’; cr
61. Transcript show: ‘hello’; cr
62. Transcript show: ‘hello’; cr “semicolon (;) is a message cascade”
64. “Expression Separators” Transcript cr. Transcript show: ‘Hi’. Transcript cr “Message Cascades” Transcript cr; show: ‘Hi’; cr
65. “Expression Separators” Transcript cr. Transcript show: ‘Hi’. Transcript cr “Message Cascades” Transcript cr; show: ‘Hi’; cr
66. “Expression Separators” Transcript cr. Transcript show: ‘Hi’. Transcript cr “Message Cascades” Transcript cr; show: ‘Hi’; cr
67. “Expression Separators” Transcript cr. Transcript show: ‘Hi’. Transcript cr “Message Cascades” Transcript cr; show: ‘Hi’; cr Functionally Equivalent
68. BLOCKS
69. [ 1 + 2 ] -> 3
70. [ :x | 1 + x ] value: 2 -> 3 “block with one parameter”
71. [ :x :y | x + y ] value: 1 value: 2 -> 3 “block with two parameters”
72. [ :x :y | x + y ] value: 1 value: 2 -> 3 # in ruby?
73. # [ :x :y | x + y ] value: 1 value: 2 (lambda {|x, y| x + y}).call(1, 2) # in ruby?
74. [ 1 + 2 ] -> 3 “even this block has an implicit message”
75. [ 1 + 2 ] value -> 3 “even this block has an implicit unary message”
76. Anything Ruby blocks can do Smalltalk blocks can also do. Probably more.
77. Some interesting stuff 10 printStringBase: 2 -> ‘1010’ 10 printStringBase: 2 nDigits: 10 -> '0000001010'
79. FLOW CONTROL
80. ( 17 * 13 > 220 ) ifTrue: [ 'bigger' ] ifFalse: [ 'smaller' ] -> 'bigger' “if/else”
81. Message a block
82. Message a block whileTrue
83. Message a block whileTrue whileFalse
84. Message a block whileTrue whileFalse Loopin’
85. Message a block whileTrue whileFalse Loopin’ Message an integer
86. Message a block whileTrue whileFalse Loopin’ Message an integer timesRepeat
87. Message a block whileTrue whileFalse Message an integer timesRepeat
88. Message a block whileTrue whileFalse Message an integer timesRepeat MEGA LOOPIN’
89. result := String new. 1 to: 10 do: [:n | result := result, n printString, ' ']. result -> '1 2 3 4 5 6 7 8 9 10 ' “to:do: on integer”
90. result := String new. 1 to: 10 do: [:n | result := result, n printString, ' ']. result -> '1 2 3 4 5 6 7 8 9 10 ' “to:do: on integer” SZUPER ÜBERLOOPIN’
91. Collection messages for looping: do reject collect detect select inject:into:
92. Collection messages for looping: familiar... do reject collect detect select inject:into:
93. MESSAGES
94. SERIOUSLY
95. Color yellow “unary message to Color class” “creates a color”
96. 100 + 20 “binary message to number 100” “I think you understand”
97. aPen go: 100 “keyword message to aPen object” “pen moves forward 100 pixels”
99. Combos
100. Pen new go: 100 “a pen is created” “pen moves forward 100 pixels”
101. aPen go: 100 + 20 “pen moves forward 120 pixels”
102. aPen go: 100 + 20 “pen moves forward 120 pixels” 1.
103. aPen go: 100 + 20 “pen moves forward 120 pixels” 1. 2.
104. RULES OF THE MODEL
105. 1. Everything is an object
106. 2. Every object is an instance of a class
107. 3. Every class has a superclass
108. 4. Everything happens by sending messages
109. 5. Method lookup follows the inheritance chain
110. A class! Object subclass: #Greeter instanceVariableNames: '' classVariableNames: '' poolDictionaries: '' category: 'Walmart' “sort of a namespace”
111. A method! greet: name | message | message := 'Hello ', name. Transcript show: message.
112. Messages! greeter := Greeter new. greeter greet: ‘Buddy’
114. Also: All methods are public. A trait is like a Ruby module. You can remove and alias methods in a trait at the time you add it to your class. Traits came after modules. Traits don’t depend on order of inclusion.
115. Seriously, everything is a message
116. Except for: variable declarations assignments returns primitives
117. There’s even doesNotUnderstand which is roughly equivalent to Ruby’s method_missing
118. Smalltalk coder’s principle:
119. Smalltalk coder’s principle: “Don’t do anything that you can push off onto someone else.”
120. Smalltalk coder’s principle: “Don’t do anything that you can push off onto someone else.”
121. VS. RUBY
122. # ruby service = WeatherForecastService.for_location "Toronto" forecast = server.forecast_for_days(5, "xml")
123. # ruby service = WeatherForecastService.for_location "Toronto" forecast = server.forecast_for_days(5, "xml") “smalltalk” service := WeatherForecastService forLocation: 'Toronto'. forecast := service forecastForDays: 5 format: 'Xml'
124. # ruby service = WeatherForecastService.for_location "Toronto" forecast = server.forecast_for_days(5, "xml") “smalltalk” service := WeatherForecastService forLocation: 'Toronto'. forecast := service forecastForDays: 5 format: 'Xml'
125. # ruby service = WeatherForecastService.for_location "Toronto" forecast = server.forecast_for_days(5, :format => "xml") “smalltalk” service := WeatherForecastService forLocation: 'Toronto'. forecast := service forecastForDays: 5 format: 'Xml'
126. # ruby if [] puts 'true' else puts 'false' end
127. # ruby if [] puts 'true' else puts 'false' end “smalltalk” (1 = 1) ifTrue: [Transcript show: 'True'] ifFalse: [Transcript show: 'False']
128. # ruby def with_blocks(block1, block2) block1.call block2.call end with_blocks(proc{ 1+1 }, proc{ 2+2 })
129. # ruby def with_blocks(block1, block2) block1.call block2.call end with_blocks(proc{ 1+1 }, proc{ 2+2 }) “smalltalk” aBlock: block1 anotherBlock: block2 block1 value. block2 value. aSomeObject aBlock: [ 1+1 ] anotherBlock [ 2+2 ]
130. Smalltalk is a written entirely in a virtual machine: View source code while app is running. Close your VM, image saved to disk. Open VM, starts up in the same exact state.
131. Smalltalkers love living in the VM: Dynamic language, but solid refactoring. Great debugging. Helpful exception tools.
132. Smalltalk had the first of the xUnit line: SUnit
133. Working in the Smalltalk VM takes you away from the world of managing files
134. SEASIDE Smalltalk on ... Internet Superhighways?
135. INSPIRATION Iowa Ruby web framework (predates Rails) INSPIRATION NeXT’s WebObjects Avi Bryant
136. State is managed for you. No XHTML templates. Generated via Smalltalk. Haml on ‘Roids.
137. DEVELOPMENT TOOLBAR Halos quick, pretty source access class browser object inspector CSS browser live edit! Profiler built in Memory view built in
138. FLOW CONTROL It’s message passing Caller is temporarily replaced by callee until callee sends answer:
139. RAILS PERSON SAYS Where are my controllers? Where’s my REST?
140. WHY DIDN’T IT CATCH ON History seems to say it was close Then Rails came Seaside attacks some difficult web dev problems Rails simplified the tedious and mundane