1. MOVE-11: Using Classes and Procedures in OpenEdge® 10
Exploiting the benefits of Object-orientation
This presentation includes annotations with additional complementary information.
Bruce S Gruenbaum
Principal Software Engineer, OpenEdge Architect Development

2. Purpose of this Talk
What are the take-aways?
Object-orientation is not a difficult transition to make
Useful addition to the language
Can improve the quality of your product
Can speed product’s time-to-market
Not an all or nothing decision
You can and should use procedural where applicable
Who is this for?
People who already know the 4GL
May have some experience writing persistent and super procedures
Wants to know about the OO stuff
Intimidated by what it is
Wants to know how to move to it
MOVE-11: Using Classes and Procedures in OpenEdge 10

3. 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 I am 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
MOVE-11: Using Classes and Procedures in OpenEdge 10

4. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

5. Why should I care about Object-orientation?
Object-orientation’s big benefits
Object-orientation is a highly structured way to build applications
Simpler modeling tool integration, e.g. roundtrip engineering
Code benefits
Less bugs
More reuse
Business benefits
Time to market
Better maintainability
Mention Model Driven Architecture, Design Centric Approach, etc
MOVE-11: Using Classes and Procedures in OpenEdge 10

6. Why should I care about Object-orientation?
How do we get the benefits?
Strong Typing
Less runtime processing
Improved quality through finding errors at compile-time
Class hierarchy known at compile-time
Re-use
Abstraction means code re-use
Classes can be deployed for re-use
Improved quality and higher productivity
MOVE-11: Using Classes and Procedures in OpenEdge 10

7. Strong Typing What is a Type? A contract with the compiler
A data type with data and behavior that conforms to a certain structure or contract
Examples of a Type
Customer with name, address, contact details and a method for purchasing from suppliers
All instances of a type are guaranteed to adhere to that contract
Type does not define how the contract was implemented
Just that it exists
MOVE-11: Using Classes and Procedures in OpenEdge 10

8. Strong Typing Implemented as Does not require runtime type-checking
Classes and Interfaces in OO
Persistent procedures and handles in procedural
Does not require runtime type-checking
MOVE-11: Using Classes and Procedures in OpenEdge 10

9. Class Customer always has PurchaseStuff (contract)
Strong Typing
Procedure
Class
/* Customer.p */
PROCEDURE PurchaseStuff:
DEF INPUT PARAMETER b
AS CHARACTER NO-UNDO.
/* buy the stuff */
END.
CLASS Customer:
METHOD PUBLIC VOID
PurchaseStuff
(INPUT b AS CHARACTER):
/* buy the stuff */
END METHOD.
END CLASS.
PurchaseStuff exists in this Persistent Procedure but not all Persistent Procedures
Class Customer always has PurchaseStuff (contract)
MOVE-11: Using Classes and Procedures in OpenEdge 10

10. Runtime Type Checking Do you have procedural code like this?
Is this a persistent procedure?
PROCEDURE InternalA:
DEFINE INPUT PARAMETER pHn AS HANDLE.
IF pHn:TYPE = “PROCEDURE” AND
CAN-DO(phn:INTERNAL-ENTRIES,“PurchaseStuff”)
AND pHn:GET-SIGNATURE(“InternalB”)
/* check sig*/ THEN
DO:
RUN PurchaseStuff IN pHn.
END.
ELSE
/* handle the error */
Does it have an internal procedure called “PurchaseStuff”?
Does the signature match?
Now we can run it
MOVE-11: Using Classes and Procedures in OpenEdge 10

11. Compile-Time Type Checking
In OO it looks like this:
METHOD PUBLIC VOID InternalA
(INPUT a AS Customer):
a:PurchaseStuff().
END.
Less Code
No runtime checking
No runtime errors
Automatically checked all 3 conditions at compile time.
Just run the thing!
Strong Typing is your friend
MOVE-11: Using Classes and Procedures in OpenEdge 10

12. The Cost of Object-orientation
Requires more forethought than procedural
Type hierarchies can be hard to change
Refactoring and modeling can help
Requires a base class library to get started
Base classes can take a while to build
Different mindset from procedural
Easier, if you have worked with super procedures before
MOVE-11: Using Classes and Procedures in OpenEdge 10

13. Object-orientation versus ProceduralOO
“Types” are created at run-time
Type definition is loosely bound
Inheritance is determined at run-time
Provides flexibility for generic code
Types are known at compile time
Type definition is contractual
Inheritance is set at design-time
Prevents run-time type errors
Dynamic code means late binding
Late binding means decisions are made at runtime
Strong typing means compile time decision making
This means less bugs
Code can execute faster because there is less to figure out
OO Code is more efficient, but more stringent
Procedural code is more flexible, but slower
MOVE-11: Using Classes and Procedures in OpenEdge 10

14. What do I use? Procedural or OO?
You don’t have to choose one or the other!!!
Use the one that is most appropriate for the task
Use procedural for generic late-bound programming
Use OO for inheritance
You can mix them
Procedural can instantiate classes
Classes can call procedures
Procedural is not going away
You don’t have to replace any procedural code with OO
MOVE-11: Using Classes and Procedures in OpenEdge 10

15. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

16. Mapping Classes to Procedures
Classes are the basis of OO development
Define data and behavior of types
Similar to persistent procedures
Can be instantiated multiple times
Have similar structure
Instantiated using NEW
Instead of RUN…PERSISTENT SET…
MOVE-11: Using Classes and Procedures in OpenEdge 10

17. Mapping Procedures to Classes
Procedure Files (.p)
Main block code
Internal Procedures
Functions
ON CLOSE
Super procedures
Class Files (.cls)
Constructor
Void Methods
Method
Destructor
Inheritance
MOVE-11: Using Classes and Procedures in OpenEdge 10

18. Mapping Procedure Structure to Class
Persistent Procedure
Class
/* Customer.p */
/* Main block code */
PROCEDURE PurchaseStuff:
END PROCEDURE.
ON CLOSE OF THIS-PROCEDURE
DO:
DELETE PROCEDURE
THIS-PROCEDURE.
END.
CLASS Customer:
CONSTRUCTOR PUBLIC
Customer():
END CONSTRUCTOR.
METHOD PUBLIC VOID
PurchaseStuff():
END METHOD.
DESTRUCTOR PUBLIC
END DESTRUCTOR.
END CLASS.
Constructor and Destructor are optional.
MOVE-11: Using Classes and Procedures in OpenEdge 10

19. Comparing Procedure Invocation To Class
DEF VAR h AS HANDLE.
RUN Customer.p
PERSISTENT SET h.
RUN PurchaseStuff
IN h.
APPLY CLOSE TO h.
DEF VAR v AS Customer.
v = NEW Customer().
v:PurchaseStuff().
DELETE OBJECT v.
MOVE-11: Using Classes and Procedures in OpenEdge 10

20. So what are the differences?
Public data members
Variables exposed outside the class
Package name
Provides path information
Access modifiers
PRIVATE, PROTECTED and PUBLIC
Classes are Types
Procedures are always just HANDLES
Public data members vs shared variables
MOVE-11: Using Classes and Procedures in OpenEdge 10

21. Additional Class Functionality
Calling code
Class
DEF VAR f AS
AR.Data.Customer.
f = NEW Customer().
f:Name = “Lift Ski”.
f:PurchaseStuff().
f:AddToInventory().
CLASS Customer:
DEF PUBLIC VAR Name
AS CHARACTER.
CONSTRUCTOR PUBLIC foo():
END CONSTRUCTOR.
METHOD PUBLIC VOID
PurchaseStuff():
END METHOD.
METHOD PRIVATE VOID
AddToInventory():
END CLASS. 1 3
Class is at AR/Data/Customer.cls 2 2 4 3 4 5 5
Doesn’t compile. Method is private.
MOVE-11: Using Classes and Procedures in OpenEdge 10

22. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

23. Procedural – OO Interoperability
You can mix them!
Procedural can call OO
OO can call procedural
You should mix them
Existing code is procedural
Some new code may be OO
MOVE-11: Using Classes and Procedures in OpenEdge 10

24. Using a Class in a Procedure
Define a global (to the procedure) variable as a class
DEF VAR c AS Customer.
c = NEW Customer().
RUN a.
PROCEDURE a:
DEF VAR c1 AS Customer.
c1 = NEW Customer().
c1:PurchaseStuff().
c:PurchaseStuff().
RUN b ( INPUT c1 ).
END PROCEDURE.
PROCEDURE b:
DEF INPUT PARAMETER p AS Customer.
p:PurchaseStuff().
Instantiate an instance
Define a local variable as a class
Instantiate a second instance
Call method on local variable
Call method on global variable
Call procedure passing class as parameter
Define parameter as a class
Call a method on the parameter
MOVE-11: Using Classes and Procedures in OpenEdge 10

25. Using a Procedure in a Class
CLASS Customer:
DEF VAR hProc AS HANDLE NO-UNDO.
CONSTRUCTOR PUBLIC Customer():
RUN Customer.p PERSISTENT SET hProc.
END CONSTRUCTOR.
METHOD PUBLIC PurchaseStuff():
RUN PurchaseStuff IN hProc.
RUN getCustomer.p.
y = DYNAMIC-FUNCTION(“getTotal” IN hProc).
END METHOD.
DESTRUCTOR PUBLIC Customer():
APPLY CLOSE TO hProc.
END DESTRUCTOR.
END CLASS.
Run a procedure persistently
Run an internal procedure
Run an external procedure
Use function dynamically
Processing procedure events
MOVE-11: Using Classes and Procedures in OpenEdge 10

26. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

27. Using Inheritance Generalized members reused by a subtype What is it?
Order
ShipDate AS DATE
METHOD ShipOrder()
InternalOrder
METHOD GetEmployeeID()
ExternalOrder
METHOD GetCustomerID()
is a
MOVE-11: Using Classes and Procedures in OpenEdge 10

28. RE-USE Using Inheritance Generalized members reused by a subtype
What is it?
RE-USE
Generalized members reused by a subtype
Order
ShipDate AS DATE
METHOD ShipOrder()
InternalOrder
METHOD GetEmployeeID()
ExternalOrder
METHOD GetCustomerID()
is a
MOVE-11: Using Classes and Procedures in OpenEdge 10

29. Inheritance Using Inheritance Generalized members reused by a subtype
What is it?
Inheritance
Generalized members reused by a subtype
Order
ShipDate AS DATE
METHOD ShipOrder()
InternalOrder
METHOD GetEmployeeID()
ExternalOrder
METHOD GetCustomerID()
is a
MOVE-11: Using Classes and Procedures in OpenEdge 10

30. Procedural Inheritance
Inheritance is available today
Through super procedures
Hierarchy established by ADD-SUPER-PROC
Use TARGET-PROCEDURE to call code in initiator
Only bound at runtime
Requires runtime resolution
No strong typing
Easy to make mistakes that are hard to find
Super can be recompiled alone
MOVE-11: Using Classes and Procedures in OpenEdge 10

31. Procedural Inheritance Example
Procedure
Super Procedure
DEF VAR h AS HANDLE.
RUN super.p PERSISTENT
SET h.
THIS-PROCEDURE:
ADD-SUPER-PROCEDURE (h,SEARCH-TARGET).
PROCEDURE a:
/* do some stuff */
RUN SUPER.
END PROCEDURE.
PROCEDURE b:
END.
PROCEDURE a:
RUN b IN TARGET-PROCEDURE.
END.
PROCEDURE b:
/* do some stuff */ 1 4 2 6 3 5
MOVE-11: Using Classes and Procedures in OpenEdge 10

32. Object Oriented Inheritance
Bound at compile time
Strongly typed - errors caught at compile-time
Subtype can be used where super type is expected
Call automatically invokes in most derived class
Hierarchy established by INHERITS statement
Changing super means a recompiles
MOVE-11: Using Classes and Procedures in OpenEdge 10

33. Object Oriented Inheritance Example
Super Class
Subclass
CLASS Parent:
METHOD PUBLIC VOID a():
b(). /* calls the one in
Child */
END METHOD.
METHOD PUBLIC VOID b():
/* do some stuff */
END CLASS.
CLASS Child
INHERITS Parent:
METHOD PUBLIC
OVERRIDE VOID a():
/* do some stuff */
SUPER:a().
END METHOD.
OVERRIDE VOID b():
SUPER:b().
END CLASS. 2 3 6 1
Syntax highlighting 4 5
MOVE-11: Using Classes and Procedures in OpenEdge 10

34. Important Things to Note
PROTECTED may only be accessed by class and subtypes
OVERRIDE is required
Tells the compiler you’re doing this deliberately
Subtype’s method is always called
May specify FINAL on Class or Method
Overriding is not allowed
Multiple inheritance is not allowed
MOVE-11: Using Classes and Procedures in OpenEdge 10

35. Interfaces Define a contract with the compiler
Guarantees a class will have certain members
No implementation in the interface
Classes implement interfaces
May be more than one
Must provide implementation for all members
Compiler validates that implementation has occurred
MOVE-11: Using Classes and Procedures in OpenEdge 10

36. Why do I need Interfaces?
To avoid this:
Avoid all that extra checking!!!
PROCEDURE InternalA:
DEFINE INPUT PARAMETER pHn AS HANDLE.
IF pHn:TYPE = “PROCEDURE” AND
CAN-DO(phn:INTERNAL-ENTRIES,“PurchaseStuff”)
AND pHn:GET-SIGNATURE(“InternalB”)
/* check sig*/ THEN
DO:
RUN PurchaseStuff IN pHn.
END.
ELSE
/* handle the error */
MOVE-11: Using Classes and Procedures in OpenEdge 10

37. Why do I need Interfaces?
Classes
Interface
CLASS Child
INHERITS Parent
IMPLEMENTS IFamily:
METHOD PUBLIC VOID c():
/* do some stuff */
END METHOD.
END CLASS.
INTERFACE IFamily:
METHOD PUBLIC VOID c().
END CLASS. 1 1
Caller 2
DEF VAR chld AS Child.
DEF VAR csn AS Cousin.
chld = NEW Child().
csn = NEW Cousin().
RUN proc(chld).
RUN proc(csn).
PROCEDURE proc:
DEF INP PAR x AS IFamily.
x:c().
END.
CLASS Cousin
INHERITS Uncle
IMPLEMENTS IFamily:
METHOD PUBLIC VOID c():
/* do some stuff */
END METHOD.
END CLASS. 1 2
MOVE-11: Using Classes and Procedures in OpenEdge 10

38. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

39. Working with OO Restrictions
OO imposes necessary restrictions
Type checking
How to write generic code?
No global variables
How to set session wide variables?
Cannot RETURN ERROR from methods
How to trap errors?
MOVE-11: Using Classes and Procedures in OpenEdge 10

40. Type Checking Use interfaces as far as possible
How to write generic code?
Use interfaces as far as possible
All classes inherit from Progress.Lang.Object
ToString()
GetClass()
NEXT-SIBLING
PREV-SIBLING
Equals()
Clone()
Use CAST function to set as subtype
MOVE-11: Using Classes and Procedures in OpenEdge 10

41. Progress.Lang.Object example
Class
Caller
CLASS Child
INHERITS Parent
IMPLEMENTS IFamily:
METHOD PUBLIC
OVERRIDE VOID a():
/* do some stuff */
SUPER:a().
END METHOD.
VOID c():
END CLASS.
DEF VAR chld AS Child.
chld = NEW Child().
RUN proc(chld).
PROCEDURE proc:
DEF INPUT PARAMETER x
AS Progress.Lang.Object.
DEF VAR z AS Child.
DEF VAR y AS Parent.
DISPLAY x:ToString().
y = CAST(x, “Parent”).
y:a().
z = CAST(x,“IFamily”).
z:c().
END.
MOVE-11: Using Classes and Procedures in OpenEdge 10

42. Global Variables Other OO languages have STATIC
How to set session-wide variables?
Other OO languages have STATIC
We will too – in the future
Need access to existing global variables
Cannot be accessed in classes
OO-Procedural interop helps
MOVE-11: Using Classes and Procedures in OpenEdge 10

43. Global Variables Example – Procedural Side
Globals.p
DEF NEW GLOBAL SHARED VAR ghAppServer AS HANDLE.
FUNCTION getAppServer RETURNS HANDLE ():
RETURN ghAppServer.
END FUNCTION.
FUNCTION setAppServerHandle RETURNS LOGICAL
(INPUT ph AS HANDLE):
ghAppServer = ph.
MOVE-11: Using Classes and Procedures in OpenEdge 10

44. Global Variables Example – OO Side
CLASS foo:
DEF VAR hGlobal AS HANDLE NO-UNDO.
CONSTRUCTOR PUBLIC foo():
RUN Globals.p PERSISTENT SET hGlobal.
END CONSTRUCTOR.
METHOD PUBLIC WorkWithGlobal():
DEF VAR hAppServer AS HANDLE NO-UNDO.
DYNAMIC-FUNCTION(“setAppServer” IN hGlobal, hAppServer).
hAppServer = DYNAMIC-FUNCTION(“getAppServer” in hGlobal).
END METHOD.
DESTRUCTOR PUBLIC foo():
DELETE PROCEDURE hGlobal.
END DESTRUCTOR.
END CLASS.
Starts the global variables procedure persistently!
Public getter and setter methods
MOVE-11: Using Classes and Procedures in OpenEdge 10

45. Error Handling Other OO languages have try… catch…
How to trap errors?
Other OO languages have try… catch…
We will have something like it too
Need to write code that traps errors today
Transactions fail, records are not found
OO-Procedural interop helps again
MOVE-11: Using Classes and Procedures in OpenEdge 10

46. Error Handling – 3 step program
Create an Error class
Make methods return or output this class
If it is not used, set the value to ?
Trap errors using procedural code
MOVE-11: Using Classes and Procedures in OpenEdge 10

47. Error Handling – Define the Error class
CLASS MyError:
DEF VAR cError AS CHARACTER NO-UNDO.
CONSTRUCTOR PUBLIC MyError(INPUT pcError AS CHARACTER):
cError = pcError.
END CONSTRUCTOR.
METHOD PUBLIC CHARACTER GetError():
RETURN cError.
END METHOD.
END CLASS.
Let’s go to the next slide to see how we use this class.
MOVE-11: Using Classes and Procedures in OpenEdge 10

48. Error Handling – Catching the Error
CLASS Customer:
METHOD PUBLIC MyError FindRecord():
DEF VAR errStat AS MyError.
errStat = ?.
FIND FIRST Customer NO-ERROR.
IF NOT AVAILABLE(Customer)
errStat = NEW MyError(“Customer not found”).
RETURN errStat.
END METHOD.
METHOD PUBLIC LOGICAL
CallFindCode(OUTPUT pcError AS MyError):
RUN find.p NO-ERROR.
IF ERROR-STATUS:ERROR THEN
pcError = NEW MyError(RETURN-VALUE).
END CLASS.
MOVE-11: Using Classes and Procedures in OpenEdge 10

49. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

50. Demo – Putting it all together
Demonstrate all the stuff we have learned
MOVE-11: Using Classes and Procedures in OpenEdge 10

51. Debugging – Memory Management
Debug  Diagnostics  Monitor Dynamic Objects…
If this area is empty you’ve done well. If there are still objects at the end you need to add a few DELETE OBJECT statements
MOVE-11: Using Classes and Procedures in OpenEdge 10

52. Agenda Why should I care about Object-orientation?
What we’re going to cover
Why should I care about Object-orientation?
Explaining OO from a procedural perspective
Procedural – OO Interoperability
Using Inheritance
Working with OO restrictions
Putting it all together
Where to from here?
MOVE-11: Using Classes and Procedures in OpenEdge 10

53. Where to from here? OO is not difficult and has some great benefits
Most of you have been doing similar code for YEARS
Procedural is alive and well
Don’t change everything
Use what you need
Lots more OO to come
MOVE-11: Using Classes and Procedures in OpenEdge 10

54. For More Information, go to…
OpenEdge 10.1A documentation
“OpenEdge Getting Started: Object-Oriented Programming”
MOVE-11: Using Classes and Procedures in OpenEdge 10

55. Great books on Object-orientation
“The Object Oriented Thought Process”
SAMS publishing
“Design Patterns”
Gamma, et al, Addison Wesley
“Patterns of Enterprise Application Architecture”
Martin Fowler, Addison Wesley
MOVE-11: Using Classes and Procedures in OpenEdge 10

56. Relevant Exchange Sessions
DEV-1: “Introduction to Object-Oriented Language Concepts and Programming in the OpenEdge ABL” with Evan Bleicher
DEV-6: “Advanced Object-Oriented Programming in the ABL” with Evan Bleicher and Shelley Chase
INNOV-14: “A Look Inside the OpenEdge UI Research Lab” with Shelley Chase and Bruce Gruenbaum
MOVE-11: Using Classes and Procedures in OpenEdge 10

57. Questions?
MOVE-11: Using Classes and Procedures in OpenEdge 10

58. Thank you for your time
MOVE-11: Using Classes and Procedures in OpenEdge 10

59. MOVE-11: Using Classes and Procedures in OpenEdge 10