1. DEV-12: Object-oriented Programming in OpenEdge® ABL
Evan Bleicher
Senior Development Manager, Progress OpenEdge

2. Terminology / Concept Review
Type - Strong-typing at compile time
Data member – state
Methods – behavior
Package – type name fully qualified
Class – Defines type; data and methods
Object – Runtime instance of a class
Interface – Set of method definitions; contract
Inheritance – Inherit / specialize from super class
DEV-12, Object-oriented Programming in OpenEdge ABL

3. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

4. CLASS Statement CLASS <class-type> [package.]classname
Single inheritence
Multiple interface
ProPath
\Acme
\Inv
\Order.cls
\Order.r
File name: Acme\Inv\Order.cls
CLASS Acme.Inv.Order:
END CLASS.
DEV-12, Object-oriented Programming in OpenEdge ABL

5. Class Statement - Optional Modifiers
FINAL
Class can not be inherited
USE-WIDGET-POOL
Creates an unnamed widget pool scoped to the class
Dynamically created handle based within the class placed in pool
Automatically deleted when class is destroyed
Can be specified anywhere in the hierarchy
DEV-12, Object-oriented Programming in OpenEdge ABL

6. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

7. Type Name Type defines Enable strong-typing
A Type is a definition
Type defines
State
Behavior
Inheritance relationship with other types
Enable strong-typing
Early binding - types determined at compile time
Type-consistency enforced at compile time and runtime
Full type names used to reference all classes
DEV-12, Object-oriented Programming in OpenEdge ABL

8. Example: Type Names DEF VAR myOrder AS CLASS Acme.Inv.Order.
DEF VAR myInternalOrder AS CLASS Acme.Inv.InternalOrder.
DEF VAR myExternalOrder AS CLASS Acme.Inv.ExternalOrder.
myOrder = NEW Acme.Inv.Order ( ).
myInternalOrder = NEW Acme.Inv.InternalOrder ( ).
myExternalOrder = NEW Acme.Inv.ExternalOrder ( ).
DEV-12, Object-oriented Programming in OpenEdge ABL

9. USING Statement (10.1B)
Supports use of unqualified class name references
Identifies a package of classes or a single qualified class
Supported in both Procedures and Class files
Applied at compile time to unqualified class names
First executable statement in file
DEV-12, Object-oriented Programming in OpenEdge ABL

10. Example: Type Names with USING
USING Acme.Inv.*.
DEF VAR myOrder AS CLASS Order.
DEF VAR myInternalOrder AS CLASS InternalOrder.
DEF VAR myExternalOrder AS CLASS ExternalOrder.
myOrder = NEW Order ( ).
myInternalOrder = NEW InternalOrder ( ).
myExternalOrder = NEW ExternalOrder ( ).
DEV-12, Object-oriented Programming in OpenEdge ABL

11. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

12. Methods Keywords defining methods Supports access modifiers
Methods define the behavior of an object
Keywords defining methods
METHOD
CONSTRUCTOR
DESTRUCTOR
Supports access modifiers
PRIVATE, PROTECTED, PUBLIC
Default is PUBLIC
Define data type it returns or VOID
DEV-12, Object-oriented Programming in OpenEdge ABL

13. Overriding Method in subclass can specialize method in super class
Specialization of methods
Method in subclass can specialize method in super class
Can replace or augment behavior in super class
Overridden method must have:
Same signature
OVERRIDE keyword
To access super class’ methods use
SUPER:method-name ( )
DEV-12, Object-oriented Programming in OpenEdge ABL

14. Example: Overriding Acme\Inv\Order.cls OVERRIDE keyword
METHOD PUBLIC DECIMAL getOrderTotal ( ):
/* Calculate total */
RETURN totalOrder.
END METHOD.
OVERRIDE keyword
Acme\Inv\InternalOrder.cls
METHOD PUBLIC OVERRIDE DECIMAL getOrderTotal ( ):
DEFINE VAR dTotal AS DECIMAL.
DEFINE VAR dDiscount AS DECIMAL INITIAL 0.85.
dTotal = SUPER:getOrderTotal ( ).
RETURN dTotal * dDiscount.
END METHOD.
Pre / Post processing
DEV-12, Object-oriented Programming in OpenEdge ABL

15. Polymorphism
Same method can perform different behavior in subclass
Execution of an overridden method in a subclass from a reference to a super class
Code written using super class
Tightly coupled to inheritance and overriding
Super class used at compile time, subclass assigned at runtime
Method call on super class dispatched to subclass’ method
DEV-12, Object-oriented Programming in OpenEdge ABL

16. Polymorphism – Example
Acme.Inv.Order
METHOD PUBLIC DECIMAL getOrderTotal ( ):
Acme.Inv.InternalOrder
METHOD PUBLIC OVERRIDE DECIMAL getOrderTotal ( ):
Acme.Inv.ExternalOrder
METHOD PUBLIC OVERRIDE DECIMAL getOrderTotal ( ):
DEV-12, Object-oriented Programming in OpenEdge ABL

17. Polymorphism - Example Continued
USING Acme.Inv.*.
DEFINE VARIABLE myOrder AS CLASS Order.
DEFINE VARIABLE bInternalCust AS Logical.
DEFINE VARIABLE dTotal AS Decimal.
IF (bInternalCust = TRUE)THEN
myOrder = NEW InternalOrder( ).
ELSE
myOrder = NEW ExternalOrder( ).
dTotal = myOrder:getOrderTotal( ).
Calls either Acme.Inv.InternalOrder or Acme.Inv.ExternalOrder getOrderTotal ( )
Super Class Reference
DEV-12, Object-oriented Programming in OpenEdge ABL

18. Benefits of Polymorphism
Supports generic programming using super class or interface
Type used at compile time is super class or interface
Specialized behavior is called at runtime automatically
Built on inheritance and overriding
DEV-12, Object-oriented Programming in OpenEdge ABL

19. Overloading (10.1B)
Multiple methods with the same name
Different behavior / same name – based on different signature
Routines with the same name
Constructors and Methods
Must have different signatures
Number, type and mode of parameters
Can not differ by only return type or access mode
No keyword to identify overloaded method
DEV-12, Object-oriented Programming in OpenEdge ABL

20. Example: Overloading No arguments One argument - integer
METHOD PUBLIC INTEGER getOrder ( ):
END METHOD.
METHOD PUBLIC INTEGER getOrder (
INPUT iCustNum AS INTEGER):
INPUT cSalesRep AS CHARACTER):
One argument
- integer
One argument - character
DEV-12, Object-oriented Programming in OpenEdge ABL

21. Widening (10.1B) Object-oriented features are strongly-typed
Widening allows passing ‘smaller’ data type for ‘larger’
Object-oriented features are strongly-typed
Data type of parameter must match
DATE  DATETIME  DATETIME-TZ
INTEGER  INT64  DECIMAL
Mode is significant – Input, Output, Input-Output
DEV-12, Object-oriented Programming in OpenEdge ABL

22. Example: Widening METHOD PUBLIC INTEGER updateSalesDate (
INPUT dtTransRecord AS DATETIME-TZ):
END METHOD.
DEFINE VARIABLE myDate as DATE.
updateSalesRecord (INPUT myDate).
DEFINE VARIABLE myDateTime as DATETIME.
updateSalesRecord (INPUT myDateTime).
DEFINE VARIABLE myDateTimeTZ as DATETIME-TZ.
updateSalesRecord (INPUT myDateTimeTZ).
DEV-12, Object-oriented Programming in OpenEdge ABL

23. Hey, how does widening affect overloading?
Follows Overloading rules:
Number of parameters must match exactly
Mode of parameter must match exactly
Relaxes data type matching rules:
With widening the caller’s data type does not have to match exactly the callee’s data type
Overloading looks for the best match
Application design concern:
May result in ambiguity error
DEV-12, Object-oriented Programming in OpenEdge ABL

24. Example: Widening with Overloading
METHOD PUBLIC INTEGER updateSalesRecord (
INPUT dtTransDate AS DATETIME-TZ,
INPUT szSalesRep AS CHARACTER):
INPUT dtTransDate AS DATE,
updateSalesRecord (INPUT myDate, INPUT “ABC”).
updateSalesRecord (INPUT myDateTime, INPUT “ABC”).
updateSalesRecord (INPUT myDateTimeTZ, INPUT “ABC”).
DEV-12, Object-oriented Programming in OpenEdge ABL

25. Example: Widening with Overloading
METHOD PUBLIC INTEGER UpdateSalesRecord (
INPUT dtTransDate AS DATETIME-TZ,
INPUT iSalesAmount AS INTEGER):
INPUT dShipDate AS DATE,
INPUT deUnitsSold AS DECIMAL):
UpdateSalesRecord (INPUT myDate, INPUT myInt64).
UpdateSalesRecord (INPUT myDateTime, INPUT myDecimal).
UpdateSalesRecord (INPUT myDate, INPUT myInteger).
Does not compile –
Ambiguity error
Does not compile – no match
DEV-12, Object-oriented Programming in OpenEdge ABL

26. Overloading: Other considerations
Interoperability remains for static / dynamic
Table / Table-Handle
Dataset / Dataset-Handle
Overloading supported for class and interface types
May result in runtime ambiguity error
Buffer-field
Dynamic-function
DEV-12, Object-oriented Programming in OpenEdge ABL

27. Raising Error (10.1B) Methods can raise error
RETURN ERROR [<error string>]
Caller handles error condition
NO-ERROR
ON ERROR phrase
Retrieve <error string> via RETURN-VALUE function
DEV-12, Object-oriented Programming in OpenEdge ABL

28. Error Raised in an Expression
All methods invoked left-to-right
Order of operands apply to results of methods
On error the result of expression is unchanged
myInt = objA:methA( ) – objB:methB( ) * objC:methC( ).
DEV-12, Object-oriented Programming in OpenEdge ABL

29. Example: Error in an Expression
myInt = objA:methA( ) – objB:methB( ) * objC:methC( ).
If methA raises error, methB and methC are not invoked
myInt’s value remains unchanged
If methB raises error, methC is not invoked
DEV-12, Object-oriented Programming in OpenEdge ABL

30. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

31. Object Instantiation Constructor of specified class is invoked on NEW
Constructor used to initialize data members
Constructor must call super class’s constructor
Via SUPER ( )
OpenEdge provides a call to the ‘default’ constructor
One with no parameters
Only if super class has no other constructor
DEV-12, Object-oriented Programming in OpenEdge ABL

32. Example: Object Instantiation
Class A
refD = NEW D (D’s params).
Invokes D’s constructor
Class B
CONSTRUCTOR PUBLIC C (C’s params ):
SUPER (B’s params).
/* C’s constructor body */
END.
Class C
CONSTRUCTOR PUBLIC D (D’s params ):
SUPER (C’s params).
/* D’s constructor body */
END.
Class D
DEV-12, Object-oriented Programming in OpenEdge ABL

33. Overloading of Constructor
Classes can have multiple constructors
Same rules as overloading for methods
Parameters specified in NEW determine which constructor is invoked
DEV-12, Object-oriented Programming in OpenEdge ABL

34. Example: Overloading One argument - Integer One argument - Character
No arguments
One argument - Integer
One argument - Character
CONSTRUCTOR PUBLIC Order ( ):
/* Constructor code goes here */
END CONSTRUCTOR.
CONSTRUCTOR PUBLIC Order (
INPUT iCustNum AS INTEGER):
INPUT cSalesRep AS CHARACTER):
DEV-12, Object-oriented Programming in OpenEdge ABL

35. Raising Error (10.1B) Constructors can raise error
RETURN ERROR [<error string>]
Caller handles error condition
NO-ERROR
ON ERROR phrase
Object reference unchanged
Destructor invoked for all classes in hierarchy whose constructor completed successfully
DEV-12, Object-oriented Programming in OpenEdge ABL

36. Example: Raising Error in a Constructor
DEFINE VARIABLE refD AS CLASS D.
refD = NEW D ( ) NO-ERROR.
IF ERROR-STATUS:ERROR THEN
MESSAGE “INSTANTIATION FAILED: “
RETURN-VALUE.
Class A
Class B
Class C
CONSTRUCTOR PUBLIC D (D’s params ):
SUPER (C’s params).
/* D’s constructor body */
RETURN ERROR “ret code 101”.
END.
Class D
DEV-12, Object-oriented Programming in OpenEdge ABL

37. Object Deletion
Destructor of specified class is invoked on DELETE OBJECT
Destructor can not be called directly
OpenEdge calls all destructors in the class hierarchy
Destructors invoked from subclass to super class
DEV-12, Object-oriented Programming in OpenEdge ABL

38. Example: Object Deletion
Class A
DELETE OBJECT refD.
Invokes D’s Destructor
Class B
DESTRUCTOR PUBLIC C ( ):
/* C’s destructor */
END.
Class C
DESTRUCTOR PUBLIC D ( ):
/* D’s destructor */
END.
Class D
DEV-12, Object-oriented Programming in OpenEdge ABL

39. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

40. Properties (10.1B) Combine data member and method
Provide getter and setter accessors
Promotes data encapsulation
Optional access mode on accessors
Caller uses Property as data member
Support data encapsulation
DEV-12, Object-oriented Programming in OpenEdge ABL

41. Example: Defining Property
DEFINE PUBLIC PROPERTY Salary AS DECIMAL
GET ( ):
/* Verify current user’s status */
RETURN Salary.
END GET.
PROTECTED SET (INPUT iVal AS DECIMAL):
/* Is it within range? */
IF ival LT THEN
Salary = ival.
ELSE
RETURN ERROR.
END SET.
DEV-12, Object-oriented Programming in OpenEdge ABL

42. Example: Accessing a Property
Same syntax as setting / retrieving a data member
Can be used in expression
EmployeeObj:Salary = newValue.
DISPLAY EmployeeObj:Salary.
DeptObj:Record (INPUT EmployeeObj:Name,
INPUT EmployeeObj:Salary).
DEV-12, Object-oriented Programming in OpenEdge ABL

43. Example 2: Defining Read-Only Property (Constant)
DEFINE PUBLIC PROPERTY pi AS DECIMAL INITIAL 3.14
GET ( ):
RETURN pi.
END GET.
DEFINE PUBLIC PROPERTY pi AS DECIMAL INITIAL 3.14
GET.
DEV-12, Object-oriented Programming in OpenEdge ABL

44. Example 3: Defining Property – not using default memory
DEFINE PUBLIC PROPERTY numUnits AS INTEGER
GET ( ):
/* Retrieve from temp-table – current value */
RETURN someTT:currentInventory.
END GET.
IF numRequested LT orderObj:numUnits THEN
orderObj:processOrder(INPUT numRequested).
ELSE
...
DEV-12, Object-oriented Programming in OpenEdge ABL

45. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

46. Compiling Tips and Techniques
Strong-typing only works if you compile – running “compile-on-the-fly” delays errors until runtime
Be safe – always rebuild/compile your code
Recompiling only super classes can result in runtime errors – always recompile subclasses that depend on super classes to be safe
Exceptions to this rule…
DEV-12, Object-oriented Programming in OpenEdge ABL

47. Compiling Tips and Techniques
Add new method
Compile
No recompile of subclasses required when:
Methods / data is added to super class
Only implementation changes, not signature
When subclass accesses new methods and data, must recompile A
Call new method
Recompile B E I C F J D G K H
DEV-12, Object-oriented Programming in OpenEdge ABL

48. Compiling Tips and Techniques
Build procedures (make.p)
Total files compiled:
MULTI-COMPILE = FALSE: 25
MULTI-COMPILE = TRUE: 8 A
COMPILER: MULTI-COMPILE = TRUE
Uses cache to store classes already compiled in session
“Cache” cleared when set to FALSE
OE Architect uses this option
Otherwise COMPILE builds full class hierarchy – no timestamp check B C D E F G H
DEV-12, Object-oriented Programming in OpenEdge ABL

49. Recommended Coding Standards
Always use packages in your type name: Acme.DAOrder
First node is your company name
Class and Interface names use Pascal Case
Interface names start with leading “I”: Acme.IList
Methods and data member use camelCase with lowercase first letter
Use object-oriented design patterns -encapsulation, abstraction, and delegation
DEV-12, Object-oriented Programming in OpenEdge ABL

50. Today’s Agenda Class Statement Type Names Methods Object Hierarchy
Properties
Interface
Class Compiler Enhancements
Roadmap 10.1C and Beyond
DEV-12, Object-oriented Programming in OpenEdge ABL

51. 10.1A Class Interface Inheritance Overriding
Access mode for data members
Strong type checking
Compiler improvements
DEV-12, Object-oriented Programming in OpenEdge ABL

52. 10.1B USING Overloading Properties
Default access mode methods - PUBLIC
Raising error from Constructor / Methods
Compiler system handle changes
DEV-12, Object-oriented Programming in OpenEdge ABL

53. Under Development D I S C L A I M E R
This talk includes information about potential future products and/or product enhancements.
What we are going to say reflects our current thinking, but the information contained herein is preliminary and subject to change. Any future products we ultimately deliver may be materially different from what is described here.
D I S C L A I M E R
DEV-12, Object-oriented Programming in OpenEdge ABL

54. Targeted for 10.1C Structured Error Handling Statics
Similar to Try, Catch, Throw
Statics
Constructors, Data Members, Methods
Character to Longchar widening
NEW function
DEV-12, Object-oriented Programming in OpenEdge ABL

55. Future Release Remote objects Strongly typed application events
Instantiating a class on the AppServer
Strongly typed application events
Publish / Subscribe for methods
Arrays of object references
Properties in interfaces
Inheritance of interfaces
Reflection
Dynamic invocation
DEV-12, Object-oriented Programming in OpenEdge ABL

56. In Summary
Object-oriented ABL supports standard object-oriented design patterns – abstraction, encapsulation, inheritance, polymorphism
ABL supports standard object-oriented constructs – interfaces, overriding, overloading, properties, strong-typing
More object-oriented functionality coming
DEV-12, Object-oriented Programming in OpenEdge ABL

57. Additional Object-oriented Exchange Sessions
DEV-6: Getting Started with Object-oriented ABL Programming (Evan Bleicher)
ARCH-7: A Class-based Implementation of the OERA (John Sadd)
ARCH-9: Using Object-oriented ABL Features in N-Tier Environment (Mike Fechner)
ARCH-12: Leveraging Design Patterns in ABL Applications (Phil Magnay)
DEV-20: Using Classes and Procedures in OpenEdge 10.1B (Phil Magnay)
DEV-12, Object-oriented Programming in OpenEdge ABL

58. For More Information, go to…
PSDN
Progress eLearning Community
What's New OE 10.1 Object Oriented Programming
Documentation
10.1B Object-oriented Programming manual
10.1B New and Revised Features manual
DEV-12, Object-oriented Programming in OpenEdge ABL

59. Questions?
DEV-12, Object-oriented Programming in OpenEdge ABL

60. Thank you for your time!
DEV-12, Object-oriented Programming in OpenEdge ABL

61. DEV-12, Object-oriented Programming in OpenEdge ABL