Smalltalk Best Practice Patterns Volume 1: Coding - Free

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ClassesThere is probably no coding decision with more effect on the quality of you code than names yougive your classes. If computers were the only audience for code we could just call them C1, C2, C3and have done. The expensive reader is not the computer, it is other people.Naming classes is your biggest billboard for communicating about your system. The first thingreaders will look at when they look at your code is the names of the classes. Those names will gobeyond your code. Insidiously, they leak into everyday conversation. And not just for developers.Ten years down the road you will hear users who know nothing about programming using the classnames you chose.Good class names provide insight into the purpose and design of a system. They reveal underlyingmetaphors. They communicate themes and variations. They break the system into parts, and showhow the parts get put back together.Great naming is an art, and will always remain so (just ask Madison Avenue). Good naming is inthe reach of everyone. Avoiding obvious mistakes and producing names that work together willboost your class names above average.Coding Patterns page 122 of 147 9/30/2006
Simple Superclass NameWhat should you call a class that is expected to be the root of an inheritance hierarchy?All naming decisions have several constraints in common. You want names that are as short aspossible, so they are easy to type and format and say. At the same time, you want to convey asmuch information as possible in each name, so readers will not have to carry as much knowledge intheir heads. You want names that are familiar, to take advantage of knowledge readers already havevia metaphor or analogy. However, you want names that are unique, so that others who are alsochoosing names will not accidentally choose names that interfere with yours.The first rule I follow is no abbreviations. Abbreviations optimize typing (a 10-100 times in 20years task) over reading (a 1000-10000 times in 20 years task). Abbreviations make theinterpretation of a name a two step process- what do the letters stand for and then what do thosewords mean. The class and method naming patterns here will produce names that you should neverhave to abbreviate.Naming the root class of a large hierarchy is a momentous occasion. People will be using the wordsyou choose in their conversation for the next 20 years. You want to be sure you do it right.Unfortunately, many people get all formal when they go to name a superclass. Just calling it what itis isn’t enough, they have to tack on a flowery, computer science-y, impressive sounding, butultimately meaningless word like Object, Thing, Component, Part, Manager, Entity, or Item.You’re creating a vocabulary, not writing a program. Be a poet for a moment. The simple, thepunchy, the easily remembered will be far more effective in the long run than some long name thatsays it all, but in such a way that no one wants to say it at all.Name a superclass with a single word that conveys its purpose in the design.There are lots of good examples in the image:NumberCollectionMagnitudeModelYou may create variations on this class, each with a Qualified Subclass Name.Coding Patterns page 123 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
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Default Value MethodYou have a comp
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Direct Variable AccessYou need to a
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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 116 and 117: implementation of queues in Pascal
Page 118 and 119: Lookup CacheHow do you optimize com
Page 120 and 121: Parsing StreamHow do you write a si
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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