Smalltalk and Object Orientation: an Introduction - Free

More documents

Recommendations

Info

26.6 Summary In this chapter you have encountered the Model -View-Controller (MVC) architecture for the first time. You have seen the basic principles behind the construction of graphical user interfaces to applications and examined the concepts of the View, the Model and the Controller. Remember these are just the basics, not only is the situation much more complicated than i ndicated here for real world applications, it varies from dialect to dialect (and in some cases from version to version). Windowing systems in general have become very powerful, this means that very large books can be dedicated to explaining the minute of a particular language and its facilities and Smalltalk is no exception. So if you want to get to know more about how Smalltalk handles graphic windows, read the manuals, examine the classes and experiment. Enjoy! 26.7 Further reading This chapter has only attem pted to provide a very basic introduction. However, there are a number of useful places for you to look for further guidance. For example [Lalonde and Pugh 1991b]. This book goes into the user interface side of Smalltalk in great detail. Some parts of it a re now out of date, however it is still an excellent reference. As always [Hopkins and Horan 1995] is an excellent reference. In particular see Chapters 29 to 34. You should also have a look at your system’s manuals, for example, the following manuals supp lied with VisualWorks are also very good references: VisualWorks User’s Guide, ParcPlace-Digitalk, Chapters 18 to 20 and the VisualWorks Cookbook, ParcPlace-Digitalk. 222
27. Graphical User Interface Construction Tools 27.1 Introduction This chapter provides a brief introduction to the VisualWorks window building facilities. The VisualWorks user interface builder is a tool which allows the developer to interactively construct a window using an object oriented drawing tool (à la MacDraw, xfig or AutoSketch). This drawi ng tool can then generate the Smalltalk source code required to actually create an instance of the window designed by the user. This Smalltalk window definition can then be easily and simply linked to a user’s application. Thus making it particularly easy to construct graphical interfaces to Smalltalk applications. This chapter is intended to provide a description of some of the features of the User Interface Painting tools. It is not intended to be a complete introduction to either the User Interface Buil der or to the instance structure of VisualWorks windows. In the remainder of this chapter we first consider what a window building tool is and then what window construction tools are available in VisualWorks (which are very similar to those tools in other Smalltalk development environments). We then consider the use of associated classes such as ApplicationModel and ValueHolder as well as how to construct windows using the availab le tools. 27.2 What is a user interface builder? A user interface builder is a tool which allows a developer to construct a window by drawing it rather than by defining it programatically. This is a very great advantage as the construction of windows in many windowing systems is unnecessarily complex and difficult to understand. It often takes a great deal of source code just to create a window, give it a label, place an input field, an output field and a button on that window. In many situations the resulting “program” is difficult to maintain and may be error prone. The result is that it is difficult to build and modify windows, whereas windowing systems by their very nature are intended to be easy to use. One approach to this problem was the construction of w indow construction toolkit. TCL/TK is an example of such a toolkit [Ousterhout 1994]. It allows the user to specify the structure of a window in a simple scripting language. The resulting window can then be integrated with a program written in another language such as C. The problem with this approach is that firstly the developer must learn the TCL scripting language, secondly they must integrate the windowing system with their C programs (not always a straight forward task) and thirdly when a bug is encou ntered they must search through two separate systems to identify where the fault occurred. In addition this approach still relies on the developer laying out the window programatically. Another approach is to use a window drawing tool. The motivation for s uch tools was to allow users to construct their windows graphically, enabling them to easily and quickly modify the window layout and then to compile the graphic window into source code. The source code could then be compiled to construct the window. In th e early days of these systems it was necessary to integrate your application code with the source code generated by the window construction tool. Having done this, if you ever modified the window, you would overwrite any application code. Obviously this wa s not acceptable, and was caused because the window construction tools were not closely integrated with a development environment. The age of the visual tool overcame this hurdle. Languages such as VisualBasic, Visual C++, Symantec’s Visual Cafe and of course VisualWorks, allow a developer to draw a window on the screen, compile it, add their own application code and modify the window without any loss of information. These tools have greatly simplified the construction of graphical interfaces and enabled a far wider range of applications to benefit from sophisticated windowing environments. 223
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 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:
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
Page 101 and 102:
11.9.3 The reject: message The reje
Page 103 and 104:
• asSortedCollection. This create
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
Page 115 and 116:
to reconstruct the data into object
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
Page 141 and 142:
Window abstract +size : Area = (10,
Page 143 and 144:
Micro Computer 1.. * Monitor System
Page 145 and 146:
connectedTo * Lamp * Weight Sensor
Page 147 and 148:
18. UML: Dynamic Modeling And Deplo
Page 149 and 150:
edisplay() Controller window A Wind
Page 151 and 152:
18.2.3.1 A start point A start poin
Page 153 and 154:
etween nodes and their stereotype.
Page 155 and 156:
OMT is a prescriptive method, it pr
Page 157 and 158:
confirming the users’ needs, thei
Page 159 and 160:
19.3.2.2 Prepare a data dictionary
Page 161 and 162:
car, truck and bus under a supercla
Page 163 and 164:
20.2.1.3 Prepare sequence and colla
Page 165 and 166:
20.2.2.5 Specify optimization crite
Page 167 and 168:
are therefore concurrent and can be
Page 169 and 170:
20.3.2.3 Design optimization The an
Page 171 and 172: 21. Frameworks and Patterns for Obj
Page 173 and 174: As the framework takes shape you sh
Page 175 and 176: about a set of classes, than to att
Page 177 and 178: instanceVariableNames: '' classVari
Page 179 and 180: 21.5.5 Running the editor You have
Page 181 and 182: Part Four Testing and Style 181
Page 183 and 184: made worse, because the symbol held
Page 185 and 186: 22.3.2 Incremental testing Incremen
Page 187 and 188: control the execution of the method
Page 189 and 190: 22.7.2 The Perform: message The per
Page 191 and 192: From the scenario that a person mig
Page 193 and 194: 23.4 Self testing An approach, sugg
Page 195 and 196: 24. Smalltalk Style Guidelines 24.1
Page 197 and 198: 24.2.4 Adding variables to system c
Page 199 and 200: should use a dictionary to hold the
Page 201 and 202: • A method should only send messa
Page 203 and 204: Table 24.2: Class message categorie
Page 205 and 206: 25. The Perform and Dependency Mech
Page 207 and 208: • Inheritance (class to class rel
Page 209 and 210: You can find the methods which impl
Page 211 and 212: These messages are sent automatical
Page 213 and 214: 26. The Model-View-Controller Archi
Page 215 and 216: and wit hdrawals and requests for t
Page 217 and 218: Figure 26.5: Part of the Controller
Page 219 and 220: model 4. update 1. balance (view) 0
Page 221: displayed. The second component add
Page 225 and 226: 27.3.1 Palette The Palette tool pro
Page 227 and 228: uild a running user interface from
Page 229 and 230: names) and the actions for buttons
Page 231 and 232: Edit button, then the user interfac
Page 233 and 234: 27.11 Visual reuse The aim of visua
Page 235 and 236: Figure 27.17: Defining the parent c
Page 237 and 238: important, as these facilities hand
Page 239 and 240: 28.3 The AddressBook class 28.3.1 T
Page 241 and 242: The aspect methods can then be simp
Page 243 and 244: the name is in the address book, it
Page 245 and 246: 29.2 The custom view widget 29.2.1
Page 247 and 248: DrawingView model SmallDraw drawing
Page 249 and 250: The action of adding a new graphic
Page 251 and 252: The next method we shall consider i
Page 253 and 254: In the updating protocol we need to
Page 255 and 256: The displaying protocol contains th
Page 257 and 258: 30. Memory Management and Garbage C
Page 259 and 260: 30.3.3 PermSpace This is used to ho
Page 261 and 262: 31. Concurrency in Smalltalk 31.1 I
Page 263 and 264: The Semaphore class provides facili
Page 265 and 266: Once the process wakes up it can de
Page 267 and 268: 31.4.3 Acknowledgments Acknowledgme
Page 269 and 270: “There are two kinds of objects i
Page 271 and 272: Object Object class Collection Coll
Page 273 and 274:
ehavior, but from the point of view
Page 275 and 276:
32.5.5 The whole enchilada Behaviou
Page 278 and 279:
33. The Future for Object Technolog
Page 280 and 281:
solutions are needed which suit the
Page 282 and 283:
scripting and query language to use
Page 284 and 285:
34. Appendix: The Smalltalk Languag
Page 286 and 287:
A capitalization convention is used
Page 288 and 289:
• marries: is the message selecto
Page 290 and 291:
Array OrderedCollection SortedColle
Page 292 and 293:
[Coleman et al 1994] D. Coleman, P.
Page 294 and 295:
OOPSLA/ECOOP’90, Joint Conference
Page 296 and 297:
detect.............................
Page 298:
True...............................
show all

Smalltalk and Object Orientation: an Introduction - Free

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?