Smalltalk and Object Orientation: an Introduction - Free

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4.6 Further reading A good paper giving some of the (historical) background on Smalltalk is [Deutsch 1989]. As an introduction to the language of Smalltalk and the VisualWorks environment you would be hard pushed to find a better book than [Lewis 1995]. If you are only going to buy one other book on Smalltalk, buy this one. Of course there are also the four Smalltalk -80 books produced by the Xerox people [Goldberg and Robson 1983], [Goldberg and Robson 1989], [Goldberg 1984] and [Krasner 1983]. 52
5. A Little Smalltalk 5.1 Introduction In the last chapter we looked at browsers and the System Transcript, in this chapter we examine Workspaces and inspectors. Workspaces and inspectors are the next most important tools in the Smalltalk system. We then consider the debugger , one of the most useful tools available to the developer. Having looked at all the major development tools you will use (at least for the time being) you are introduced briefly to the Smalltalk language. You will then use the tools available to write some Smalltalk. 5.2 The Workspace Workspaces are a kind of direct interface to the system c ompiler. They act a bit like an editor in that you can type Smalltalk code into them, and execute that code immediately. You can define temporary and global variables, create instances of classes, perform arithmetic calculations et c. The only thing you cannot do is define classes and methods (that must be done in one of the browsers). In the following figure, the Workspace is being used to calculate the average of a set of numbers. To compile code within a Workspace you first select the code using the left mouse button. You then bring up the Workspace operations menu using the right mouse button (if you have a three mouse button you will use the middle button). This menu is also illustrated in Figure 5.1. The fourth grouping on the menu contains do it, print it and inspect. The do it and print it operations will compile and execute the code. do it will merely run the code, while the print it operation will also prin t the result of executing the last expression selected. The result is left highlighted so that you can delete it with the delete key if you no longer require it. Try them out and see for yourself. The inspect operation will first compile the code (if requi red) and then open an inspector (see below) on whatever you currently have selected. It the system was consistent, this option would be called “inspect it”. You can have as many Workspaces as you require open, you are not limited to a sin gle Workspace. Of course on a standard PC or Macintosh screen, you may be limited by space. This highlights another issue, for developing Smalltalk systems, it is often useful to have as much screen “real estate” as you can get. Bigger really is better in this case. Figure 5.1: Using the Workspace 53
Page 1 and 2: Smalltalk and Object Orientation: A
Page 3 and 4: Chapter 7: Smalltalk Constructs Thi
Page 5 and 6: The user interface construction fac
Page 7 and 8: Preface 1. INTRODUCTION TO OBJECT O
Page 9 and 10: 12.5 A CLASS SIDE METHOD...........
Page 11 and 12: 27.3 VISUALWORKS WINDOW PAINTING TO
Page 13: Part One Introduction to Object Ori
Page 16 and 17: interfaces between different parts
Page 18 and 19: een to ease the transition from one
Page 20 and 21: encapsulation. Attempting to introd
Page 22 and 23: is a controversial subject which is
Page 24 and 25: will become second nature to many o
Page 26 and 27: or return something. It has since b
Page 28 and 29: defining the behavior of different
Page 30 and 31: In time most developers start to ac
Page 32 and 33: 2.4.3.4 Smalltalk environments are
Page 34 and 35: 3. Constructing an Object Oriented
Page 36 and 37: Wash wipe switch Wiper motor Relay
Page 38 and 39: Point 2 above is more complicated.
Page 40 and 41: services working? working? working?
Page 42: Part Two The Smalltalk Language 42
Page 45 and 46: other systems. As the browsers, ins
Page 47 and 48: VisualAge (a version of Smalltalk w
Page 49 and 50: 4.5.2 The VisualWorks Launcher and
Page 51: Class categories. These are group s
Page 55 and 56: Notifiers can be displayed under a
Page 57 and 58: These concepts of messages, receive
Page 59 and 60: Select the “Debug” option. This
Page 61 and 62: 6. Smalltalk Building Blocks 6.1 In
Page 63 and 64: 6.3.1 Class definitions In Smalltal
Page 65 and 66: Object Class1 Class 2 method search
Page 67 and 68: “Now calculate y “ y := x * 23.
Page 69 and 70: 7. Smalltalk Constructs 7.1 Introdu
Page 71 and 72: They are more efficient for storage
Page 73 and 74: 7.5.3 true, false and nil variables
Page 75 and 76: anArray at: 1 max: 10. This will tr
Page 77 and 78: Figure 8.1: Defining a new class 8.
Page 79 and 80: this convention at the moment, howe
Page 81 and 82: 9. Control and Iteration 9.1 Introd
Page 83 and 84: 9.3.3 Block temporary variables Blo
Page 85 and 86: The brackets round the 1 to: 10 are
Page 87 and 88: OrderedCollection class (respective
Page 89 and 90: holding other objects. Typically, c
Page 91 and 92: | temp | temp := Set new. temp add:
Page 93 and 94: Next we will define a message proto
Page 95 and 96: 11. Further Collection Classes 11.1
Page 97 and 98: for (i = 0; i
Page 99 and 100: x inspect. This has some similariti
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• asSortedCollection. This create
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Figure 12.2: The Organizer class de
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12.6 The private-updating protocol
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do: [:item | Transcript show: item
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13. Streams and Files 13.1 Introduc
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Notice that in this example we used
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to reconstruct the data into object
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1. The ability to save the current
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14.3 The class Date Class Date, a s
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aCharacter isAlphabetic. aCharacter
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Breakpoints may be placed in a me t
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If the file does not exist you will
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Figure 15.4: Creating a project To
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Part Three Object Oriented Design 1
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16. Object Oriented Analysis and De
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devolved amongst the objects). This
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driving force behind the whole of t
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17. The Unified Modeling Language 1
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Deployment diagrams . Deployment di
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Window abstract +size : Area = (10,
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Micro Computer 1.. * Monitor System
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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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