SEM03 Having Fun with VFP (some samples from VFX)

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SEM03Having Fun with VFP(some samples from VFX)

• Rainer Becker
• Rainer.Becker_at_dFPUG.de

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Rainer Becker

• dFPUG
• Incorporated UG
• Portal.dfpug.de
• German DevCon
• Tenth time price
• Localization Toolkit
• German, French, Czech (with Igor Vit)
• Visual Extend
• MVP, MCP
• Wizards Builders

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Mixed Topics Basic Directions

• What are we talking about in general and in this
  session

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Original Session description

• There are a lot of concepts in VFP that are
  different from the official theory but help us
  with rapid application development. This session
  will show a set of examples when, where and why
  using VFP is a great advantage in software
  development, at least if you know what you are
  doing. Many of these subtitles might sound like
  contradictions in itself but maybe you can still
  use them in your day to day work, e.g.
  COM-servers made visible, database without
  integrity rules, VFP for Excel-users,
  read-only-access-methods, labels for checkboxes,
  segmented tables and other topics are presented
  in a fast paced tips tricks fashion.
• Session title might be misleading

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Topics

• Concepts of Visual FoxPro in General
• Concepts of Visual Extend in General
• Contradictive Example Visible COM-Servers
• Thumb databases are more intelligent
• Configuration with Dynamic Constants
• Main Work is user interface misc. Tipps

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Concepts of Visual FoxPro and Visual Extend

• Just to remind you of some basic stuff

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Visual FoxPro Capabilities

• Free unlimited application distribution
• Free unlimited database distribution
• Free unlimited reportwriter distribution
• Just add MODI REPO ? to your menue
• All in one tool (everything you need)
• Partially via integration (Help, Install)
• Fine-Tuned over a decade of development
• Lifecylce extended to 2014 with VFP 9

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Visual FoxPro Language

• Hybrid programming language
• Procedural (great for batch jobs)
• Self-modifying code
• Data-aware commands
• Compiled commands for local database engine
• Object-based (like Visual Basic)
• But Using Containers instead of SimpleFrame
• Object-oriented (with Business Objects)
• Ignoring theory of total encapsulation

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Visual FoxPro Database

• Hybrid database commands
• Fast Xbase table commands (records)
• SQL (groups, CURrent Set of recORds)
• Mixed use (xbase on cursor), but my favorite
• Replace all a.val with b.val for seek( a.key,
  b)
• Compiled database access
• Critic no strict type checking in language
• Vice versa always database comand strings

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Visual FoxPro Special

• OOP Special
• Awareness of parent and all other objects
• Container subclassing incl. ActiveX-Controls
• Ease of Redirection of subclassing
• Not Collection-oriented only
• PROG Special
• Evaluate, Macro, Excescript, Compile
• Definition files are tables
• Command window for direct execution

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Visual Extend Capabilities

• Proven framework with standard functions
• Rich set to enhance enduser application
• Builders for Rapid App. Development
• Standardized Design Layout
• Standard forms for various tasks
• Grid-Page for search, Edit-Pages for detail
• Sourcecode included except Builders
• No Business Objects, just 2-Tier-Apps

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Rapid Application Development

• 2 tiers are most often enough for a good and fast
  application of small to medium size
• Customers often are not willing to pay much
  higher price for maybe lower maintenance cost in
  the future
• Business functions can still be encapsulated in
  classes which are to be used by the GUI, but
  these do not have to be clean BOs

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Rapid Application Conversion

• If you do not try to re-invent the wheel
  conversion of FoxPro/Windows applications with
  the help of a framework is pretty fast-forward as
  you can take over tables, reports and batch-code
• It is kind of a re-write but not really as you
  can reuse your knowledge and rebuild the
  application very fast in VFP

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Recommendation

• Software-architecture is very interesting
  andthree-tiered appswith business objectsare
  very powerfull
• But only if you can afford them or your client is
  willing to pay the way
• Otherwise stick to RAD VFP / VFX is best suited
  for and build sell apps

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Visible COM-Servers

• You were always told to use Business Objects in
  the middle tier with the advantage they can be
  re-used via COM

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Main object

• COM-Server need one OLE-Public object
• this does not have to be a business object
• Most often BO are not best choice to be accessed
  directly from outside of the application!
• It has to be an object
• a wrapper for a BO is needed at least
• Based on control or container
• Called via createobject from other apps
• Methods/properties are accessable so they have to
  be protected

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Access/Assign and Parameters

• Protect Methods / Properties
• Small Interface Hide Properties / Methods
• Extensive parameter checking in Methods
• Add Assign-Methods to Properties
• Assign- Access-Methods
• Vartype and allowed values (list, valid date)
• Formatting (Uppercase, remove spaces)
• Read-only properties
• Internal access only (hidden property switch)

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Additional Preparation

• Check startmode
• INLIST( _vfp.startmode, 2,3,5 )
• disable automation server unattended mode
• SYS(2335,1)
• Integrate error handling
• COMRETURNERROR
• Should also be called from access/assign-methods
• Set all your settings
• Reminder Press StrgOK in Options dialog

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Project Definition

• Add a main program just to have it
• Your test program is a good main program
• Include Metadata-tables in project
• Include Config.fpw in project
• SCREEN OFF (invisible VFP desktop)
• RESOURCEOFF (prevent foxuser creation)
• ALLOWEXTERNALON (additional config)
• Make visible when needed

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Application Execution

• Example in Excel
• Dim loRef as Object
• On Error Goto SomeError
• Set loRef createobject(exe.obj)
• other operations
• Set loRef Nothing
• Excel developers love VFP-data-access as it is
  much easier for them then ODBC/ADO!

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Application Rollout

• Runtime Directory contains
• ltYourservergt.exe
• VFP8R.DLL, VFP8RENU.DLL
• GDIPLUS.DLL
• REGSVR32.EXE
• MSVCR70.DLL to system32
• Regsvr32.exe vfp8r.dll
• ltYourservergt.exe /regserver

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Recommendation

• We use WinWord, Excel, Outlook, Internet Explorer
  and other applications by calling them
• Why dont we provide the same VISIBLE
  function-ality to our customers?
• Especially Excel-/Word developers are
  interested!gt additional market

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Intelligent Databases are a problem for
programmers

• Why make your live even more complicated ?

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Reasons for a dumb datastore

• Switching backends is a nightmare if validations
  are additionaly stored in the database (including
  key generation/RI)
• Temporary saving of invalid records is helpfull
  for a lot of users (lActive/lValid)
• Synchronization is a disaster if records can only
  be added with correct parent/child-relations set

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Recommendation

• If you want to use different backends
• No valids, RI, triggers
• No DBCX
• Handle logic in apps
• A lot of developers have good experience in
  practise with dumb datastores for switching and
  synchronisation

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Dynamic Constants

• Repetition how to use constants and additional
  ways to use Constants for later application
  configuration

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Constants Basics

• DEFINE CONSTANT Value
• Not working within or
• compared to , example ?WB with m.b defined
• But working within
• UNDEFINE CONSTANT
• Only in program or current method
• Use INCLUDE or Class/Form dialog
• Multiple levels of inclusion possible

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Conditional Constants

• IF condition (constant or VFP function)
• ELSE, ELIF cond, ENDIF
• IFDEF, IFNDEF constant
• ELSE, ENDIF
• Some examples
• INCLUDE Foxpro.h / Messagebox-example
• IF .F. for comments
• Do not use DEFINE IF .F. (optimized)
• Except for temporary exclusion of complete class

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More exciting use for constants

• Array dimensions and column names
• laTemp( lnCounter, CONST_COL_NAME)
• Translation of strings
• lcMessage CONT_MSG_TEXT
• Replacement of commands
• LOCATE FOR CONT_LOC_COND
• Version dependent functionality
• Both for VFP as well as own version
• Comment out SUSPEND, DEBUG
• DEFINE SUSPEND , DEBUG
• Not working any more Commentblock
• See above, DEFINE BeginComment IF .F. not
  working

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Real world examples

• Example 1 / Profiler
• Constants for Tablenames, Boundaries, Captions,
  Colors, Classes, Combined Messages
• Example 2 / VFXSync
• Constants for Steps / Messages, Metatablenames,
  Metafieldnames, Parameter lists, locate
  statements, logfilenames, aliases

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In-Between-Code

• Place constants before and after calls
• DEFINE BEFORE/AFTER/WITHIN
• INCLUDE useroverwrite.h
• Use running status-variable
• For IF/ENDIF-blocks
• To change running var within code
• No need for calls to emtpy methods
• Longer compilation time but faster runtime

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Recommendation

• You can increase the configurability of your
  sourcecode with constants
• Only in case you really need to configure you
  change the header-file.
• No performance penalty compared to table-driven
  or any other way to configure your apps

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Main work is stillthe user-interface

• Most time is still spend of user interface design
  and validations

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GUI-functions encapsulation

• Very powerfull Textmerge()-function can be used
  in a variety of ways
• Addressformatter
• Addressabreviator (not IntelliSense)
• Build in button-click and when done save as class
  for reuse on other forms
• You do not have to go multi-tier, but still it is
  an advantage to use classes and subclassing if
  you separate out user interaction
  (spagetthi-code!)

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Source example TextMerge()

• Format-Memofield contains various
  ltltalias.fieldnamegtgt in correct position plus
  hardcoded addtional information like country
  short code
• SELECT adressformat
• LOCATE FOR adressformat.country lcCountry
• AND adressformat.active .T.
• IF FOUND()
• lcFormat adressformat.format
• lcFormat TEXTMERGE( lcFormat )
• IF NOT EMPTY( lcFormat )
• lcMessage "adress copied to clipboard"
• _CLIPTEXT lcFormat
• ENDIF
• ENDIF

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Recommendation

• Important is not to clutter code all over your
  forms but to place them in a central place, might
  it be buttons in a classlib or a business object
• Important is to allow for GUI-mode and just a
  function call with return value

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Famous last words

• Use Visual FoxPro in the right way for you and
  your applications

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More and more functionality
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Fast development experience

• With VFP alone as well as with additional tools
  and frameworks

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Best tool for fast development

• .NET is stillnot ready
• PHP / mySQLno option
• VFP will be extended even further
• Good option for now as 4 GL

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Thank You!

• Please do not forget the evaluation form!
• Visit our websites
• www.dfpug.de
• portal.dfpug.de
• forum.dfpug.de
• wiki.dfpug.de
• www.visualextend.de
• www.visualfoxpro.de
• www.wizards-builders.com