Smalltalk Best Practice Patterns Volume 1: Coding - Free

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self listPane parentcolor: Color black;height: 17width: 11At a glance, you can’t tell whether height and width are set separately or together. The readabilitygains of a Cascade are quickly lost if you have to spend any time figuring out the messages that aresent. Fortunately, most times messages go to the same receiver (especially more than two), themessages are simple.You may have to use Yourself if you are using the value of a Cascade.Coding Patterns page 136 of 147 9/30/2006
YourselfYou need to use the value of a Cascade.How can you use the value of a Cascade if the last message doesn’t return the receiver of themessage.This has got to be the number one confusing method in all of Smalltalk. There it is in Object, whereevery new Smalltalker stumbles across it:Object>>yourself^selfOr, if the programmer was really clever (and didn’t know about Interesting Return Value):Object>>yourselfWhat’s going on?Let’s say you want to add a bunch of elements to an OrderedCollection. Collection>>add: anObjectis defined to return anObject, not the receiver of the message. If you want to assign the Collectionto a variable:all := OrderedCollection newadd: 5;add: 7Will result in the value of all being 7. There are two solutions to this problem. The first is to put thevariable assignment in parentheses:(all := OrderedCollection new)add: 5;add: 7When you need the value of a Cascade and the last message does not return the receiver,append the message “yourself” to the Cascade.Our example becomes:all := OrderedCollection newadd: 5;add: 7;yourselfSending “yourself” returns the receiver, the new instance of OrderedCollection. That’s the objectthat gets assigned to the variable.I’ve seen folks become defensive about “yourself”, tacking it onto every Cascade they write. Youshouldn’t do this. Yourself is there to communicate to your reader that you really want the value ofthe receiver used, not the result of sending a message. If you aren’t using the value of a Cascade,don’t use yourself. For example, I wouldn’t use it in Point>>printOn:, because I don’t assign thevalue of the Cascade to a variable or return it as the value of the method.Coding Patterns page 137 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
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Collection Accessor MethodYou are u
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Enumeration MethodYou are using Ind
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Role Suggesting Instance Variable N
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Temporary VariableA Composed Method
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Caching Temporary VariableA Perform
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Reusing Temporary VariableTemporary
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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
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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 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 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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