There are a few important ways that Smalltalk is different then other languages:

Transcription

1 The Presenters Ginny Ghezzo: Project Manager for IBM VisualAge Smalltalk and Level 3 support for the Application Builder Craig Chaney: Technical Lead on the Virtual Machine, Communications and Linux development The Smalltalk Environment There are a few important ways that Smalltalk is different then other languages: 1. The Simplicity The Smalltalk syntax fits on an index card. a. There are six reserved words in Smalltalk. b. There are three types of expressions. Smalltalk becomes a study of class libraries and not memorization of syntax 2. The Image The creation and execution of code take place in the same object space called an image. Smalltalk environments do not produce standalone executables for a program. 3. Development Cycle You do not need to compile and link your code. Any changes to the source code are immediately compiled into the classes in the image. This lends itself to incremental development. 4. All source code is visible Two benefits Lecture 3 Object-Oriented Languages and Systems 1

2 1. You get to see examples of code. 2. You know exactly what a particular method is going to do for you and return to you. You are browsing the environment to determine the class/methods to use The Programming Cycle 1. Write classes and methods using the Browser Tools in the environment 2. Execute the code to test if it works. This is usually done in Workspaces or Browsers. 3. Debug any problems you encounter in the debugger. 4. For Production Applications you would do another step called packaging. VisualAge Smalltalk Enterprise V5.5.2 Downloadable at under the topic Download VisualAge Smalltalk Version Tools System Transcript The main window in VisualAge Smalltalk. One and only one System Transcript. Workspaces Workspaces are a simple text pane to try out code. Lecture 3 Object-Oriented Languages and Systems 2

3 File -> New: Creates a new Workspace File -> Open: Opens an existing Workspace Three ways to interact with expressions Execute: Evaluate the expression but do not display the results. Display: Evaluate the expression and display the value Inspect: Evaluate the expression and open an Inspector on the result. Execute, Inspect, Display are available anywhere you can type in code. Inspector A window in which one can see and manipulate an object. Examples o Inspect 3+4 o Inspect OrderedCollection with: Smalltalk with: is with: good. Changing the value of an object or its variables o Change the value directly with File->Save o Change the value by executing methods o To bind the value of self to a variable use Bind self to selection Lecture 3 Object-Oriented Languages and Systems 3

4 Some useful Inspector menu items: o File -> Revert: Changes the contents of the text pane back to its previous contents. Browsers o Variable -> Inspect: Brings up a new inspector window on the selected object. o Variable -> Update: If the object s value has changed since the inspector was opened or saved will display the new value. o Variable -> Browse Class: Brings up a browser that displays the class definition Lecture 3 Object-Oriented Languages and Systems 4

5 Task Add a new application Change prerequisites for an application Add new classes to an application See all classes for one application Add new methods to a class for one application Add new methods to a class for any application See all methods for a class for all applications See all methods that use a specific method or that have the same name Inspect code and dictionaries Find errors in code Package applications into runtime images See what applications are in the library See all editions and versions of a component Assign team members ownership of specific components Configure components to support multiple platforms Find differences in code among components and editions of Browser(s) Application Manager, Applications Browser, Organizer Application Manager, Organizer Applications Browser, Application Browser, Classes Browser, Hierarchy Browser, Organizer Application Manager, Applications Browser, Application Browser, Organizer Applications Browser, Application Browser, Classes Browser, Hierarchy Browser, Class Browser Applications Browser, Classes Browser, Hierarchy Browser Class Browser, Classes Browser, Hierarchy Browser Methods Browser Inspector Debugger Application Manager, Configuration Maps Browser, Packager Control Browser, Organizer Application Editions browser, Configuration Maps Browser, Shadow Application Browser Application Editions browser, Class Editions Browser, Method Editions Browser, Configuration Maps Browser Application Manager, Configuration Maps Browser, Organizer Configuration Maps Browser, Application Editions browser Application Changes Browser, Changes Browser, Text Comparison Lecture 3 Object-Oriented Languages and Systems 5

6 components Analyze the performance of code Browser Benchmark Workshop, Memory Monitor Applications Browser An Application is a group of related classes that are functionally related and can be used as a unit. Every class in VisualAge Smalltalk belongs to one application. A Prerequisite is an application that is required by another application o Example: CommonFileSystem is a prerequisite to any application that reads or writes to a file. o Application Manager Browser Prerequisite Menu has tools to determine prerequisites A Subapplication is an application that is contained with in an application o Used to separate Operating System Specific Code o Subapplications are not used very often To open use the tool menu and select Browse Applications: The first pane lists all applications that are loaded. The second pane lists the classes in that application. Lecture 3 Object-Oriented Languages and Systems 6

7 The third pane lists the categories defined in the class The fourth pane lists the method names in that category To create an application, perform Application -> Create -> Application VisualAge Smalltalk creates a Class that is the same name as the application. To create a Class, perform Classes-> Add-> Subclass Directly add instance variables, class variables and pool dictionaries Can change the class you are subclassing from Changing the name of the class will create a new class Methods-> New Method Template Change the methodpattern of an already created method Public and Private are solely for the convenience of developers and will not affect the access to methods during execution. To create a Method, To create a categories, With a class highlighted, Categories-> Add With a method highlighted, Method->Categories->Add To Categories Categories are solely for the convenience of the developers and will not affect the execution of the methods. Useful menu options available in most browsers Applications Find Application: Finds an application in the left hand pane Find Class: Finds a class within the application selected Classes Browse References: Allows you to see all references to various types of objects used by this class. Lecture 3 Object-Oriented Languages and Systems 7

8 Categories Methods Browse Messages: Allows you to find the senders/implementers of a method restricted to the hierarchy of the selected class. Browse Class: Opens the class browser on the selected class Browse Hierarchy: Opens the Hierarchy Browser on the class. This will tell you all of the superclasses for the class. Add: Adds a new category for this class Rename: Allows you to change the name of the category selected Delete: Deletes the category. If any methods are in this category they move to Not Categorized. This will not delete any methods. Select All By Default: A toggle that when selected will highlight all categories when a class is selected. Visibility: Changes which methods will show up in the method pane based on the level selected in the hierarchy. Browse Senders: Shows all methods that send the selected method Browse Implementers: Shows implementation of all methods with the same name. Browse Messages: Shows all classes that send any method that this method sends. Load: Allows you to bring in a different edition of the method. Code Management There are two parts of VisualAge Smalltalk 1. The Client, which is your development environment 2. The Code Manager, which stores all of the code a. Keeps a version of every saved change to a method Lecture 3 Object-Oriented Languages and Systems 8

9 b. Tracks which developer made the change c. Allows you to compare changes in your code An Open Edition is a state that allows you to change a class or application. All methods are considered editions when saved. Versioning instructs VisualAge to preserve a class or application s contents. A version cannot be changed. A new edition must be opened to change the class or application. Releasing instructs VisualAge to load that particular version of a class or subapplication if anyone loads its containing application. Exporting Applications There are two ways to share code with other Managers. 1. File In/File Out: Creates a flat text file containing the source code of any method, class or Application. 2. Import/Export: Creates a little manager with the Application code. a. Creates a.dat file that can be shared with others. ENVY\Smalltalk Debugger The Debugger is displayed when an exception is thrown. Lecture 3 Object-Oriented Languages and Systems 9

10 The five panes of the debugger are: 1. Process List: Gives you a list of all of the processes you are debugging. 2. Message Stack: The messages that were executing when the debugger was opening 3. Variables: All visible variables including temporary variables defined in the current method. 4. Variable Values: The current value of the variables that are selected 5. Description Pane: The code for the method. The expression sent is highlighted. There are four ways you can step through the code in the stack. 1. Into: Displays the code and takes you into the method selected. 2. Over: Executes the message without displaying the method s source. 3. Return: Execute the rest of the current method up to the return statement. 4. Resume: Continue the current process until it completes Useful functions: Lecture 3 Object-Oriented Languages and Systems 10

11 Processes->Debug Other Shows a list of currently running processes and allows you to select them to be displayed in the debugger. Processes->Remove from list: Removes the selected process from the list in the debugger but does not terminate the process. Processes->Terminate: Terminates a process and removes it from the process list. Stack->Drop to Selected Frame: Restarts the execution from the top of the stack. Remember you are re-executing some code and the effects of the first run have not been undone. There are five ways to get the debugger to come up 1. From the System Transcript under the Tools Menu 2. By executing a self halt. This is most commonly used when you need to stop within a workspace script 3. An exception is thrown because of a code problem 4. Clicking on the User Exit Button 5. A breakpoint is encountered. Initial Windows When you start the VisualAge Smalltalk environment (abt.icx) and have connected to the code repository, three windows will be opened. VisualAge Smalltalk Click Here to Interrupt Execution Lecture 3 Object-Oriented Languages and Systems 11

12 System Transcript The system transcript is a special instance of Workspace with three unique features. Can access the HTML help through the help menu. Access various browsers, the debugger, view your breakpoints and access to your code manager from the tools menu Is accessible as a global variable, Transcript, for printing messages to. VisualAge Organizer The VisualAge Organizer is a graphical browser of applications Lecture 3 Object-Oriented Languages and Systems 12

13 Has all of the capability of the Application Browser when full menus are on. Give you access to special editors o Composition Editor: Visual code Builder through parts. o Script Editor: Add Smalltalk code in methods (like the Class Browser) o Public Interface Editor: Define interfaces into created parts and generate scripts\methods Additional Information Newsgroup: ibm.software.vasmalltalk Please use this for any and all questions about VisualAge Smalltalk support list: oova-consult@csc.ncsu.edu Please use this for questions that arise in the course of doing your homework. Documentation Our books are available in PDF format at 4.ibm.com/software/ad/smalltalk/library/v55docs.html Lecture 3 Object-Oriented Languages and Systems 13

14 Searchable helps and books are installed with the product. Installation Will probably not need the additional features. Downloading from the Web lets you choose 2 big files (client and manager) or 14 small files. Getting Started VisualAge Smalltalk Getting Started: A basic application using visual parts. How Do I Help : Has some useful basic information on applications, packaging, etc. Other Dialects Lecture 3 Object-Oriented Languages and Systems 14

15 For more information on the various dialects of Smalltalk see or Examples from Class Scripts Methods balance: anamount balance:= anamount balance ^balance withdraw: anamount self balance: (self balance anamount) deposit: anamount self balance: (self balance anamount) isnegative ^self balance < 0 openaccount: initialbalance ^self new balance: balance; yourself. ticker ticker := OrderedCollection with: 1. ticker inspect. [ 20 timesrepeat: [ ticker at: 1 put: (ticker first + 1). (Delay forseconds: 1) wait. ] ] fork. [ [ true ] whiletrue: [ (Delay forseconds: 1) wait ] ] forknamed: 'Our cool delay loop' Lecture 3 Object-Oriented Languages and Systems 15