mike fechner, consultingwerk ltd. pug finland, thursday, 25h 2010 object-orientation in the abl...
TRANSCRIPT
Mike Fechner, Consultingwerk Ltd.
PUG Finland, Thursday, 25h 2010
Object-orientation in the ABLCapabilities and features
… and limits
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Consultingwerk Ltd.
Independent IT consulting organisation Focussing on OpenEdge and .NET Progress Consulting Partner, long running
cooperation with PSC Located in Cologne, Germany Consulting, conception, coaching, development,
training , mentoring, review Customers located in Germany, Europe (EU, CH),
USA Vendor of tools and consulting packages
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Consultingwerk Ltd.
20 years of Progress experience (V5 … V10) Progress, OpenEdge, ADM2, Dynamics,
OERA, Sonic MQ/ESB OpenEdge GUI for .NET early adaptor (hands
on since 10/2006) .NET (C#) experience since 2002 (.NET 1.0) in
combination with the OpenEdge Proxy objects Almost no Java experience (but I’ve been said
it’s a copy of C# - or vice versa )
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Object-orientation in the ABL
Introduction Comparing OOABL to procedural Comparing OOABL to C# OO with GUI for .NET OERA and OO discussions in the community
Object-orientation in the ABL
Often referred as OOABL– Some people in PSC dislike that term. It‘s not
a new language. But it‘s much shorter than the „object-oriented extensions to the ABL aka 4GL“
Adds coding constructs like classes, object instantiation, methods, access types etc. to the ABL
Constructs well known from (other) OO languages like C# and Java
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OOABL time line
10.1A first implementation, classes, objects, methods, properties (but I’m not 100% sure about that)
10.1B Interfaces, USING statement, properties (when not part of 10.1A)
10.1C Static members, structured error-handling, properties in Interfaces, DYNAMIC-NEW
10.2A GUI for .NET, garbage collection for objects (anything reference by a WIDGET-HANDLE or COM-HANDLE is not an object)
10.2B Abstract classes, abstract members, .NET generic type definition, strong typed events, reflection part 1
OE11: No major new OO feature announced – so far
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OOABL: Why?
Common way of coding, known to every young developer. Universities don’t teach procedural programming at all
Market trend that PSC could not resist anymore, didn’t want to be the only modern non OO language
Simply the way people want to code today. True for ABL?
GUI for .NET! No way to leverage the .NET framework without OO
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OOABL: Why? Different way of coding, breaking tasks into smaller
chunks, agile coding, Unit-Testing, reusability (but we believe the ABL is the most powerful language to maintain spaghetti code)
Interfaces, Design Patterns, often quoted Guru’s (not sure if everybody read their books)
Martin Fowler (UML, OO architecture, transformation) GoF, Gang of Four, Erich Gamma et al., often quoted
in source code (i.e. GoF 175 – decorator pattern)
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OOABL: Members of a class
Constructor(s) Destructor Methods, overloaded methods, polymorph meth Properties
– Data members– Variables (primitive and reference types)– Defined non OO objects, Temp-Tables,
ProDatasets Events
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Demo / Sample code
IBusinessEntity Interface BusinessEntity class proSIretrieve.p Class Browser
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Object-orientation in the ABL
Introduction Comparing OOABL to procedural Comparing OOABL to C# OO with GUI for .NET OERA and OO discussions in the community
Comparing OOABL to procedural
The compiler and runtime enforce OO concepts (but not good OO design )– strong-typing, type safeness
Concepts like inheritance or encapsulation are part of the language
ADM2 implemented them in the language Object instance is very similar to a persistent
procedure: Launched by someone else, life cycle, private and public members
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Comparing OOABL to procedural
Comparing SUPER class to SUPER procedure Both allow „inheriting“ behaviour by using methods
and procedures of the SUPER thing SUPER procedure: Manual task to run or locate
that, SUPER class: Just INHERIT Shared SUPER procedure: Data Members
(Variables, Temp-Tables, Buffer, …) shared among childs, SUPER class: individual to every single child
Child class won‘t compile with error in SUPER class
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TABLE-HANDLE parameter
A SUPER procedure expecting a TABLE-HANDLE parameter can be overloaded with a TABLE parameter
Compiler doesn‘t care (know about it) Runtime is fine with that This is not possible with classes:
– Method with TABLE-HANDLE cannot be overridden by method with TABLE parameter
– Interface method with TABLE-HANDLE parameter cannot be implemented using TABLE
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Dynamic coding
Procedures– RUN VALUE („…“) . RUN VALUE („…“) IN hProc.– DYNAMIC-FUNCTION, {fn}, {fnarg}– INTERNAL-ENTRIES property– DYNAMIC-CALL
OO– Don‘t do that Except DYNAMIC-NEW – DYNAMIC-NEW (10.1C), DYNAMIC-INVOKE (10.2B)– No dynamic access to properties– No possibility to query available members
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AppServer
The AppServer protocol only speaks procedural Every client needs to call into procedures Activate, Deactivate, Connect, Disconnect
procedures AppServer may use objects from there on Can‘t pass an object as a parameter between
AppServer and Client Can‘t remotely call into an object like we can into a
remote persistent procedure (not recommended, but possible)
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Garbage collection
For true objects only (Progress.Lang.Object, System.Object)
Instace is removed automatically when nobody knows about it anymore
The fact that the DB objects (query object handle, buffer object handle) are called objects is misleading. In fact they should be called widgets
A must have safety rope for large (OO) systems
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GLOBAL SHARED Variables
Classes and objects don‘t have access to these Static properties are much more powerful anyway But to introduce first OO features in an application
this may be an issue
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Static classes
… classes with only static members Easiely build a framework that needs no startup Usably from procedures and classes Build static wrappers to exisiting framework APIs
(Dynamics managers) But can‘t be unloaded at all! When static classes
have access to DB tables, you won‘t be able to disconnect the DB at runtime
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Demo / Sample code
Wrapping Dynamics Managersinto (static) classes
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Object-orientation in the ABL
Introduction Comparing OOABL to procedural Comparing OOABL to C# OO with GUI for .NET OERA and OO discussions in the community
C#
The original language of the .NET Framework Java like Developed by MS after they wered allowed to
modify Java anymore 100% object-oriented
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C#
Everything (in the .NET framework) is an object, most objects you can inherit from and that is how you code– DataView, DataTable, DataSet, DataRow
In the ABL most language features are pre OO– Query, Temp-Table, ProDataset, Buffer– No inheritance from built in language features
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Subclassing Data Structures
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class Temp-Tables
ttOrder
«column» OrderNum OrderDate CustomerNum
ttCustomOrder
«column» OrderNum OrderDate CustomerNum HighPriorityFlag Comments
DEFINE ttCustomOrder LIKE ttOrder FIELD HighPriorityFlag FIELD Comments
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class DataRow Inheritance
System.Data.DataRow
Your.Application.OrderRow
Your.Application.Custom.SpecialOrderRow
Similar to a buffer or a recordAllows dynamic access to fields using a (weak typed) collection
Static access to fieldsStrong typedPotentially validation rules (triggers)
Static access to additional fields
inherits
inherits
OO ABL’s missing features
Collections to handle „groups“ of object instances Generic types to make Collections type safe and
easy to use Serialization, ability to persist object state (data
members) or transport accross the wire
ABL can only query (Temp-)Tables Browser can only show records in a query ProBindingSource needs qeury as well
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Object-orientation in the ABL
Introduction Comparing OOABL to procedural Comparing OOABL to C# OO with GUI for .NET OERA and OO discussions in the community
OO ABL with GUI for .NET
A perfect match (in 10.2B) Hybrid ABL classes act like .NET objects Inheritance, Interface Implementation Event handling ABL can declare .NET Collections and generic
types A hybrid instance may be used in a .NET Collection
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Demo
Class browser Progress .NET Objects Microsoft .NET Objects (+ generics) Infragistics Classes ABL classes
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Object-orientation in the ABL
Introduction Comparing OOABL to procedural Comparing OOABL to C# OO with GUI for .NET OERA and OO discussions in the community
OERA and OO discussions
Progress OERA (John Sadd, Mike Omerod)– ProDataset central role– OO Code to manage ProDataset and Queries
and validation etc.– ProDataset exposed to others (no real
encapsulation of –internal- data)– Difficulties with sub-classing data due to missing
language capabilities– Little work to build and maintain, good ABL fit
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OERA and OO discussions
Model-Set-Entity Pattern (Phil Magnay)– http://communities.progress.com/pcom/messa
ge/72716#72716– ProDataset centric, but encapsulated– Huge evolution of John Sadd‘s original
patterns– „Facade“ objects to access and manipulate
records– Used in large development projects, source
code not availableObject-orientation in the ABL 32
OERA and OO discussions
Very often like religious war… Looooooooong threads, looooooong posts In a language that has nothing to do with classical
ABL speak Mostly debated is the role of relational concepts
like Temp-Tables and ProDatasets in the Business Logic
Classic ABL coding is often underestimated (my opinion)
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OERA and OO discussions
PABLO (Thomas Mercer Hursh)– No use of ProDataset and Temp-Tables in a
Business Logic– A single instance represents each record– Lazy instantiation to solve (potential)
performance issues– XML serialization– Sub-classing no problem– But: No real implementation available
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Questions ?
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Thank you !