Smalltalk and Object Orientation: an Introduction - Free

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Instance based reuse is more complicated to achieve but has the advantage that the required functionality is also obtained. 27.11.3 Inheritance of canvases Subcanvas reuse as described above really relates to part-of relations hips and must be redefined for each window which wishes to use the same subcanvas even if all the windows relate to subclasses of a common ancestor class. ApplicationModel ProjectApplicationModel AccountModel commonSpec behaviour accountSpec account behaviour accountSpec commonSpec Figure 27.16: Inheritance of subcanvases One way of alleviating this duplication is to use inheritance with the reuse of parts of a graphical user interface. For example, rather than obtaining the subcanvas specification from another class, the subcanvas specification is inherited from a parent class. This is illustrated in Figure 27.16. This enables not only part of the window layout to be inherited, but instance variables, accessor methods and value holder relationships etc. This can be done by s pecifying the inherited window specification containing the required layout, in the canvas property of a subcanvas widget. 27.12 Method of working with the UI builder At this point it is worth noting the sequence of steps (and their order) which are generally ta ken when developing a window using the user interface builder. We will assume that we are constructing a new window on a new class. The only differences that you need to bear in mind if this is not the case is to ensure that you don’t over write existing w indow specifications or method definitions (unless that is what you intend to do). 1. Open the user interface builder using the canvas icon on the Visual Launcher and draw the desired window. 2. Once you have drawn the window, select Install from the canvas too l. This will bring up the installer window (illustrated in Figure 27.6) with an empty class name. You must enter a class name before you can continue. 3. Having specified a class name the window illustrated in Figure 27.17 will be displayed. As we are defining a new window we select the Application option in the Define As grouping which results in the ApplicationModel class being selected as the super class of our newly defined class. If we wish the class to be defined in a category other than UIApplications-New, then we also need to specify the category (if this does not already exist it will be created). We can now select OK. 4. This returns us to the installer where we have the option of specifying a window specification name other than windowSpec. Remember windowSpec will be used as the default window layout when a window is opened. This is done by typing in a new name into the box below the prompt saying “or enter new Selector”. 5. We are now ready to define any action methods, accessor method etc. for the window. This is done using the Define button on the canvas tool. This causes the definer window to be displayed (as illustrated in Figure 27.9). 6. You are now ready to define any additional initialization code required. Once this is done you can start the window using the Open button on the canvas tool. 7. Any subsequent editing of the window follows a similar pattern. However you will not be prompted for the superclass nor category of the class again. 234
Figure 27.17: Defining the parent class and category 27.13 Summary In this chapter you have learnt about the VisualWorks window construction tools their use and the concept of value holders. You have also been told about the modifications introduced in VisualWorks to the basic MVC framework and the difference between application models and domain models. 235
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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
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other systems. As the browsers, ins
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VisualAge (a version of Smalltalk w
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4.5.2 The VisualWorks Launcher and
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Class categories. These are group s
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5. A Little Smalltalk 5.1 Introduct
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Notifiers can be displayed under a
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These concepts of messages, receive
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Select the “Debug” option. This
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6. Smalltalk Building Blocks 6.1 In
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6.3.1 Class definitions In Smalltal
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Object Class1 Class 2 method search
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“Now calculate y “ y := x * 23.
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7. Smalltalk Constructs 7.1 Introdu
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They are more efficient for storage
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7.5.3 true, false and nil variables
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anArray at: 1 max: 10. This will tr
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Figure 8.1: Defining a new class 8.
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this convention at the moment, howe
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9. Control and Iteration 9.1 Introd
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9.3.3 Block temporary variables Blo
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The brackets round the 1 to: 10 are
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OrderedCollection class (respective
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holding other objects. Typically, c
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| temp | temp := Set new. temp add:
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Next we will define a message proto
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11. Further Collection Classes 11.1
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for (i = 0; i
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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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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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