Smalltalk and Object Orientation: an Introduction - Free

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state of your development environment when you saved it. VisualWorks system. Figure 4.1 illustrates the structure of the Virtual Image Smalltalk Virtual Machine Host Computer (tools, system classes, user classes, instances) Figure 4.1: VisualWorks system structure When you deliver systems to clients it is poss ible to cut down to a minimum what you deliver (e.g. you probably won’t need to give a client the compiler classes). To do this a number of tools are available including the stripper tool (which strips out those parts of the image you don't need) provided as a utility with VisualWorks. When you work with a Smalltalk system you should be aware of at least two files (besides your own source files). One is referred to as the Virtual Machine (this is also known as the Object Engine ) and one is referred to as an Image file (see Figure 4.2). The image file is an “image” of the state of your development at a particular point in time as described above. To actually use VisualWorks you need to run the image o n the virtual machine. This means that you can have different images on your file system possessing different sets of classes, in different states, all of which can be run by the same virtual machine. It should be noted, however, that it is only possible t o run one at a time on a single invocation of the virtual machine. Image file Changes file Visual.im Visual.cha VW.exe Virtual Machine Figure 4.2: Primary files in VisualWorks Finally, another file that you should be aware of is the changes file . This file lists all the modifications you make to any class, as well as the instructions you issue to the system (e.g. to accept some code). In fact it is the changes file which holds the uncompiled version of your source code. The relationship between the files in VisualWorks is thus that illustrated in Figure 4.2. Note that there are in fact other files used by the system (e.g. such as the VisualWorks sources file - called Visual.sou). However, at present you do not need to worry about them. 48
4.5.2 The VisualWorks Launcher and Transcript Figure 4.3: The VisualWorks Launcher and Transcript, a System Browser and a Workspace When VisualWorks is first started up, the user will see the Launcher and the system Transcript as illustrated at the top of Figure 4.3. This illustrates VisualWorks on a Windows -95 system, however, it looks identical on a Macintosh or a UNIX box. We shall consider the Launcher and Transcript separately as they will be used by the developer in different ways. 4.5.2.1 VisualWorks Launcher The VisualWorks Launcher is the primary w ay in which you will access the tools within the VisualWorks environment. You should think of it as the top menu bar across most PC and Macintosh applications, like the start button on Windows -95 or like the pop -up menu used with many X windows desktops. I t is your interface to VisualWorks. From the Launcher you can access all the system browsers (for browsers also read editors), the screen painting tools, the database tools, help, file access tools etc. As you use VisualWorks more and more you will come to know where these tools are and how to use them. For speed of access a number of the most used tools have button icons below the menu bar. These are (from left to right): • The file tool (for browsing directories, editing files on the host file system and filing in (a bit like compiling) files. • The System Browser, which is described below. • Open a Workspace (see below for an explanation of Workspaces). • The Screen Painter which is used to easily and quickly construct graphical interfaces. • The Resource Finder which is used to find window and icon definitions. • Database tools for working with relational database systems • The on-line help system. The most important operations other than those covered above are Exit VisualWorks ... and SAVE AS. Both of these operations are found under the File menu. The Exit VisualWorks ... operation allows the user to quit from VisualWorks at any time. This operation brings up a pop -up window with three options, Exit, Save + Exit and Cancel. The Exit options quits VisualWorks and the current state of the system is not saved and thus anything that you have done (including coding) since you last saved will be lost. Remember that when you define new classes and methods you are only doing so within the VisualWorks environment, you are not saving anything to file. There is a way to recover anything you have done, if you quit and have forgotten to save your image, which involves the changes list which we won’t look at yet. The Save + Exit option first saves the image and then exits VisualWor ks while the Cancel option, returns the user to the VisualWorks environment. The SAVE AS operation saves the current state of your VisualWorks environment as an image. Look back in this chapter if you are not sure what an image is. This image can be re -started again at a later date. 49
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: VisualAge (a version of Smalltalk w
Page 51 and 52: Class categories. These are group s
Page 53 and 54: 5. A Little Smalltalk 5.1 Introduct
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:
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Page 95 and 96: 11. Further Collection Classes 11.1
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x inspect. This has some similariti
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11.9.3 The reject: message The reje
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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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