Smalltalk and Object Orientation: an Introduction - Free

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10.9 Summary In this chapter you have encountered for the first time, one of the most important class hierarchies in Smalltalk. The various collection classes will form the basis of the data structures you build and will be the corner stone of most of your implementations. So far you have looked at Bags, Sets and OrderedCollections. For those of you coming from a Lisp style language these concept s won’t have seemed too strange. However, for those of you coming from languages such as C, Pascal or Ada you may well have found the idea of a bag and a set quite bizarre. Stick with them, try them out, implement some simple programs using them and you wi ll soon find that they are easy to use and extremely useful. You will very quickly come to wonder why every language doesn’t have the same facilities! Figure 10.5: The System Browser after the "next" method has been defined 10.10 Further reading Almost any good book on Smalltalk includes a detailed discussion of the collection classes. However, particularly good references can be found in [Lalonde and Pugh 1991]. Useful references for the Queue and Stack classes can be found in [Goldberg and Robson 1989]. 94
11. Further Collection Classes 11.1 Introduction This chapter continues the discussion of the collection class hierarchy. It concentrates on the ordered collections and builds on the previous chapter. Sections two, three an d four present the SortedCollection class, the List class and the Interval Class. The Array class, Dictionary class and String class are presented in Sections five to seven. Section eight describes how to iterate over collections while Section nine explai ns how to convert between collections. Figure 11.1 illustrates the relationships between some of the ordered collection classes. Figure 11.1: Some of the ordered collection classes 11.2 SortedCollection A SortedCollection is a collection class in which the order of the elements is determined by a specified sorting criteria (for example x i < x i+1 ). This is specified by the sort block associated with every sortedCollection object. That is, the ordering is defined by a special block of code (for example, [:x :y | x>= y]). This block can be replaced by the user of the class so that any type of ordering can be applied to the objects with in the collection. Why not browse the class using the class browser. Try and find out what type of sorting algorithm is being used. Try out the following in a Workspace: | x | x := SortedCollection new. x add: 5. x add: 6. x add: 7. x add: 1. x inspect. 95
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Smalltalk and Object Orientation: A
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Chapter 7: Smalltalk Constructs Thi
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The user interface construction fac
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Preface 1. INTRODUCTION TO OBJECT O
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12.5 A CLASS SIDE METHOD...........
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27.3 VISUALWORKS WINDOW PAINTING TO
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Part One Introduction to Object Ori
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interfaces between different parts
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een to ease the transition from one
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encapsulation. Attempting to introd
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is a controversial subject which is
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will become second nature to many o
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or return something. It has since b
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defining the behavior of different
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In time most developers start to ac
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2.4.3.4 Smalltalk environments are
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3. Constructing an Object Oriented
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Wash wipe switch Wiper motor Relay
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Point 2 above is more complicated.
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services working? working? working?
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Part Two The Smalltalk Language 42
Page 45 and 46: other systems. As the browsers, ins
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Page 49 and 50: 4.5.2 The VisualWorks Launcher and
Page 51 and 52: Class categories. These are group s
Page 53 and 54: 5. A Little Smalltalk 5.1 Introduct
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Page 59 and 60: Select the “Debug” option. This
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Page 65 and 66: Object Class1 Class 2 method search
Page 67 and 68: “Now calculate y “ y := x * 23.
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Page 81 and 82: 9. Control and Iteration 9.1 Introd
Page 83 and 84: 9.3.3 Block temporary variables Blo
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Page 89 and 90: holding other objects. Typically, c
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Page 105 and 106: Figure 12.2: The Organizer class de
Page 107 and 108: 12.6 The private-updating protocol
Page 109 and 110: do: [:item | Transcript show: item
Page 111 and 112: 13. Streams and Files 13.1 Introduc
Page 113 and 114: Notice that in this example we used
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Page 117 and 118: 1. The ability to save the current
Page 119 and 120: 14.3 The class Date Class Date, a s
Page 121 and 122: aCharacter isAlphabetic. aCharacter
Page 123 and 124: Breakpoints may be placed in a me t
Page 125 and 126: If the file does not exist you will
Page 127 and 128: Figure 15.4: Creating a project To
Page 129 and 130: Part Three Object Oriented Design 1
Page 131 and 132: 16. Object Oriented Analysis and De
Page 133 and 134: devolved amongst the objects). This
Page 135 and 136: driving force behind the whole of t
Page 137 and 138: 17. The Unified Modeling Language 1
Page 139 and 140: Deployment diagrams . Deployment di
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connectedTo * Lamp * Weight Sensor
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18. UML: Dynamic Modeling And Deplo
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edisplay() Controller window A Wind
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18.2.3.1 A start point A start poin
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etween nodes and their stereotype.
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OMT is a prescriptive method, it pr
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confirming the users’ needs, thei
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19.3.2.2 Prepare a data dictionary
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car, truck and bus under a supercla
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20.2.1.3 Prepare sequence and colla
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20.2.2.5 Specify optimization crite
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are therefore concurrent and can be
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20.3.2.3 Design optimization The an
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21. Frameworks and Patterns for Obj
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As the framework takes shape you sh
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about a set of classes, than to att
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instanceVariableNames: '' classVari
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21.5.5 Running the editor You have
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Part Four Testing and Style 181
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made worse, because the symbol held
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22.3.2 Incremental testing Incremen
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control the execution of the method
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22.7.2 The Perform: message The per
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From the scenario that a person mig
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23.4 Self testing An approach, sugg
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24. Smalltalk Style Guidelines 24.1
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24.2.4 Adding variables to system c
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should use a dictionary to hold the
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• A method should only send messa
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Table 24.2: Class message categorie
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25. The Perform and Dependency Mech
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• Inheritance (class to class rel
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You can find the methods which impl
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These messages are sent automatical
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26. The Model-View-Controller Archi
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and wit hdrawals and requests for t
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Figure 26.5: Part of the Controller
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model 4. update 1. balance (view) 0
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displayed. The second component add
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27. Graphical User Interface Constr
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27.3.1 Palette The Palette tool pro
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uild a running user interface from
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names) and the actions for buttons
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Edit button, then the user interfac
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27.11 Visual reuse The aim of visua
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Figure 27.17: Defining the parent c
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important, as these facilities hand
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28.3 The AddressBook class 28.3.1 T
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The aspect methods can then be simp
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the name is in the address book, it
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29.2 The custom view widget 29.2.1
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DrawingView model SmallDraw drawing
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The action of adding a new graphic
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The next method we shall consider i
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In the updating protocol we need to
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The displaying protocol contains th
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30. Memory Management and Garbage C
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30.3.3 PermSpace This is used to ho
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31. Concurrency in Smalltalk 31.1 I
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The Semaphore class provides facili
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Once the process wakes up it can de
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31.4.3 Acknowledgments Acknowledgme
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“There are two kinds of objects i
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Object Object class Collection Coll
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ehavior, but from the point of view
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32.5.5 The whole enchilada Behaviou
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33. The Future for Object Technolog
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solutions are needed which suit the
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scripting and query language to use
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34. Appendix: The Smalltalk Languag
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A capitalization convention is used
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• marries: is the message selecto
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Array OrderedCollection SortedColle
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[Coleman et al 1994] D. Coleman, P.
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OOPSLA/ECOOP’90, Joint Conference
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detect.............................
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True...............................
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