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

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

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

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

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

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

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

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

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

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

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

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

Object-orientation versus Procedural OO “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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

MOVE-11: Using Classes and Procedures in OpenEdge 10