TfxLocate Component (c) 1997 by Chuck Gadd.

All rights reserved.



You are granted permission to use this component in any program royalty-free.

You may not charge any fee for distributing this component.  Use of this component

is at your own risk.  I do not make any warranty regarding this component, but

it's based on code I've used for quite a while.  (Ok, so I'm not good at lawyer-talk )



I make no promises regarding Updates/bug fixes, but if you find any bugs or have any

feature suggestions, please let me know.  My email address is [email protected]

Feel free to drop me an email just to say 'I like it!'.  If you hate it, don't bother

telling me.





Description:

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LOCATEs data in a TTable or TQuery component (and their descendants like

the Infopower TwwTable component ).  Currently only searches on String and Blob/Memo

fields.  Will search up to 1048576 chars of a Blob/Memo field. (Does anyone know the

stated limits of a dBase/Paradox blob/memo?)   Starting with Version 0.90, it will

automatically find and use an index if one is available for the field being searched for.





What's New in v0.9x:

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Index Optimization : Will examine all available indexes, and use one if it matches.  This

                    will greatly improve speed.  See "Optimizing" below for more info.



Progress tracking : You can now specify an event to trigger every N records.

                   This will let you display progress to your users.



Adjustable Memo/Blob Buffer size : Was hard-coded to 32767, now you can set it anywhere

                                  from 1 to 1048576.







Installation:

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for Delphi 1, from the main menu choose: Options|Install Components|Add

for Delphi 2 and Delphi 3 choose: Component |Install|Add

then browse to find the Dir where you unzipped this components files.

It will be installed onto the Samples page.



ATTENTION!!!!!!!!!!!!!!!

Before installing ANY components, you should make a safe copy of your

Delphi Library files (or in the case of D3, the Package files).  If it gets mangled, you're hosed!!!!



I haven't had any problems with this component trashing my VCL, but why take chances???





Properties:

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UseIndexes : If True, the component will check the available index

            files, and attempt to optimzie the Locate or LocateNext

            Commands.  See section 'Optimizing' below for more info.

            If False, no Optimization will be attempted.



ProgressCount : The OnProgress event will be triggered after every

               N records.  This allows you to show a status or progress

               information to your users.  If this is set to 0, the

               OnProgress event will not be called.



MaxMemoSize : Specifies the size of the buffer to be used for searching

             memo/blob fields.  If the memo is greater than the size

             specified here, only the part that fits in this buffer

             will be searched.  The default is 32767, with a max of

             1048576.  This memory is only allocated while a search

             on a memo/blob field is active.



Datasource : The datasource component to search



Datafield : The name of the String or Blob field to search



FindText : The string value you want to find.



MatchType :

       maAnywhere : finds text anywhere in the field

       maFull : field must match text exactly

       maBeginning : text must match beginning of field



IgnoreCase : If true, the search will be case insensitive



DisableControls : If True, disables all attached components during

       search.  Greatly increases speed, but it looks cool to leave

       controls enabled during the search. ;^)



FindCursor : The cursor that will be displayed during the search.



FailPos : Where to leave the record pointer if no match is found:

       fpOriginal : Position record pointer to starting record

       fpEnding : Leave record pointer at the last record checked

       fpBottom : Leave pointer at bottom of table

       fpTop : Leave pointer at top of table



DoBackground : Determines whether the component releases time for other

       windows processing to occur during the search.  Recommended

       while searching very large tables.



NumRecs : Number of records to examine.  If zero, searchs until EOF.



RUNTIME/READONLY PROPERTIES:

-----------------------------



Found : True if Locate/LocateNext was successful.



Error : Error condition (if any) that caused the Locate to fail

       erNone : No error, data just not found.

       erDataset : Dataset not set, or not Active.

       erField : Field not correct type, or not present.

       erUnknown : I have no idea!



Optimized : True if an index was used to optimize the Locate/

           LocateNext.  If this returns false, OptError will

           indicate the reason it was not Optimized.



OptError : Error condition that caused Optimized to be false.

          erOptNone : No error (Possibly UseIndex set to false)

          erNoInd : No index was found for the field

          erMatchType : "Anywhere" matches can not be optimized

          erCaseSens : The IgnoreCase setting did not match the

                       case sensitive flag of the index.

          erNotTable : Only TTable datasets can be optimized.

          erNotReady : The DataSource is not set, or is not

                       Active.







Methods:

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Locate : Performs a locate from the Top of the Dataset.



LocateNext : Performs a locate from the NEXT record.



TestOptimized : Determines if the next Locate/LocateNext will

               be Optimized, based on current settings.







Events:

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OnFind : Called when the data was successfully found.



OnFail : Called when the data was NOT found.



OnProgress : Called every N records, where N is determined by

            the ProgressCount property.







Optimizing:

-------------------------------------------------------------

If the Field you are Locating has an active index, TfxLocate can find the index,

and use it to optimize the Locate/LocateNext commands.  There are several

limitations:



1)  An index on the field must exist.  If the index is based on multiple fields,

   the field you are Locating must be first.  dBase "Expression" indexes will

   not be used.



2)  If the IgnoreCase property is True, then the index must also be "Case Insensitive".



3)  MatchType must be maFull or maBeginning



4)  Searches on Memo/Blob fields can not be optimized.



4)  The DataSet must be a TTable or Descendant.



There is a new Method, TestOptimize that will test the parameters, and determine if

the Locate/LocateNext will be optimized.



After a Locate/LocateNext or TestOptimize, you can check the Optimized property to

determine if it was optimized.  If it was not, you can check the OptError to determine

the reason it was not optimized.  If it was not optimized, check the OptError property to

determine why.



For an example of using these new features, check out the included Demo app.





TfxLocate Source Code:

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Currently, source code is NOT available.  Sometime soon, source will be

made available for a low "registration fee".  Email me if you wish to be

notified when the source is available.  The component itself will continue

to be free for unrestricted use (Except as stated in the first paragraph).

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