Smalltalk Best Practice Patterns Volume 1: Coding - Free

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implementation of queues in Pascal using a header record. I followed pretty well, a first for me,when I got a conviction that there was a shorter implementation.I could see nothing but my notebook as I scrambled to code in my head and then on paper a versionthat used a footer record instead. Sure enough, I could slice one line out of one of the routines.After class I hustled over to the computer center to try it out. Bingo! It ran. I rushed over toAndrzej’s office to show him my gem. He was skeptical at first, but we went over it and hecongratulated me on my success. It was the first time I’d spoken to a professor one-on-one. I wasoverwhelmed.I have since given up computer science for software engineering, but writing this has given me arenewed sense of how important that little bit of transformation was for me.Coding Patterns page 116 of 147 9/30/2006
Searching LiteralHow do you search for one a few literal objects known when you write the code?If Smalltalk had a case statement, you would be tempted to writeCharacter>>isVowelcase self asLowercase of$a:$e:$i:$o:$u: ^trueotherwise: ^false(I’m suggesting case statement syntax. A Choosing Message is almost always better than hardcoded cases, anyway.)Since Smalltalk doesn’t have a case statement, you generally have to resort to Boolean orconditional logic:Character>>isVowel| lower |lower := self asLowercase.^lower = $a | (lower = $e) | (lower = $i) | (lower = $o) | (lower = $u)Pretty ugly, eh? Not as bad as:Character>>isVowelself = $a | (self = $A) ifTrue: [^true].self = $e | (self = $E) ifTrue: [^true].self = $i | (self = $I) ifTrue: [^true].self = $o | (self = $O) ifTrue: [^true].self = $u | (self = $U) ifTrue: [^true].^falseBecause Strings are literals, you can use the collection protocol to implement the same thing muchmore compactly:Character>>isVowel^’aeiou’ includes: self asLowercaseYou can do the same thing with Symbols:Style>>isFancy: aSymbol^#(bold italic) includes: aSymbolThis is not a trick that comes up every day, but used occasionally it can save you a few lines ofcode.Ask a literal collection if it includes the element you are looking for.Coding Patterns page 117 of 147 9/30/2006
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Smalltalk Best Practice PatternsVol
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STATE..............................
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PrefaceThis preface will explain wh
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AcknowledgmentsI would like to than
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Many of the patterns tell you what
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day to day in development and docum
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What’s Missing?There are a few co
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AdoptionHow can you learn and use t
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Why Patterns WorkHere is the Big As
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Role of PatternsReadingThese patter
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BehaviorObjects model the world thr
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Composed MethodYou are implementing
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Complete Creation MethodA Composed
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ConversionHow do you convert inform
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Converter Creation MethodYou need t
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Query MethodA Composed Method has h
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Execute Around MethodHow do you rep
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MessagesMessages are the heartbeat
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Choosing MessageYou are using a Mes
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Decomposing MessageYou are using a
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Intention Revealing SelectorYou may
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Integer>>addFloat: aFloat^self asFl
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Class: SuperFindingClientsuperclass
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Extending SuperYou are using Super.
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DelegationA Composed Method needs w
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Self DelegationYou are using Delega
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Pluggable BehaviorHow can you param
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Pluggable BlockYou need complex Plu
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marriedMenAndUnmarriedWomen^self ma
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Instance VariablesI wrote the secti
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Variable StateHow do you represent
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Timer>>defaultMillisecondPeriod^100
Page 66 and 67: Default Value MethodYou have a comp
Page 68 and 69: Direct Variable AccessYou need to a
Page 70 and 71: Getting MethodYou are using Lazy In
Page 72 and 73: Collection Accessor MethodYou are u
Page 74 and 75: Enumeration MethodYou are using Ind
Page 76 and 77: Role Suggesting Instance Variable N
Page 78 and 79: Temporary VariableA Composed Method
Page 80 and 81: Caching Temporary VariableA Perform
Page 82 and 83: Reusing Temporary VariableTemporary
Page 84 and 85: CollectionsThe collection hierarchy
Page 86 and 87: CollectionHow do you represent a on
Page 88 and 89: RunArrayYou are using an OrderedCol
Page 90 and 91: | s |s := Set new.Like an OrderedCo
Page 92 and 93: You may need Double Dispatch for co
Page 94 and 95: DictionaryYou need a Collection tha
Page 96 and 97: SortedCollectionYou have a Collecti
Page 98 and 99: ByteArrayYou need to represent an A
Page 100 and 101: (1 to: anArray size) collect:[:each
Page 102 and 103: IsEmptyHow do you test if a collect
Page 104 and 105: ConcatentationHow do you put two co
Page 106 and 107: DoHow do you execute code for each
Page 108 and 109: Select/RejectHow do you execute cod
Page 110 and 111: Inject:into:You need an Enumeration
Page 112 and 113: Duplicate Removing SetYou have a Co
Page 114 and 115: StackHow do you implement a stack?O
Page 118 and 119: Lookup CacheHow do you optimize com
Page 120 and 121: Parsing StreamHow do you write a si
Page 122 and 123: ClassesThere is probably no coding
Page 124 and 125: Qualified Subclass NameYou have cre
Page 126 and 127: FormattingNo other topic generates
Page 128 and 129: Type Suggesting Parameter NameYou a
Page 130 and 131: Rectangular BlockYou are writing an
Page 132 and 133: Conditional ExpressionHow do you fo
Page 134 and 135: Simple Enumeration ParameterWhat sh
Page 136 and 137: self listPane parentcolor: Color bl
Page 138 and 139: Point>>printOn: aStreamaStreamprint
Page 140 and 141: Development ExampleIn this chapter,
Page 142 and 143: Money>>setAmount: aNumber currency:
Page 144 and 145: MoneySum>>printOn: aStreammonies do
Page 146: | m1 m2 |m1 := Moneyamount: 5curren
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Smalltalk Best Practice Patterns Volume 1: Coding - Free

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