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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 100000 THEN Salary = ival. ELSE RETURN ERROR. END SET. DEV-12, Object-oriented Programming in OpenEdge ABL

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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DEV-12, Object-oriented Programming in OpenEdge ABL