[Solved] SQLite | GetTableNames desnt work
lazarus / 16-Databases

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cpalx · 2018-02-14 18:31

hello, i use
TSQLite3Connection
and i need The tebles names, so i use

TSQLite3Connection.GetTableNames(a Tstrings)

and i get a memory error

any idea?

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molly · 2018-02-14 18:47

Quote from: cpalx on February 14, 2018, 07:31:28 pmany idea?
without any code and exact error message ?, no idea.

In that case your guess is as good as mine....

Shot in the dark: you did not create your stringlist before passing it
along to method GetTableNames...

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cpalx · 2018-02-15 02:06

================
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
 SQLiteConn:= TSQLite3Connection.Create( nil );  Query:=
TSQLQuery.Create( nil );  SQLiteTran:= TSQLTransaction.Create( nil ); 
SQLiteConn.Transaction:= SQLiteTran;  Query.Transaction:= SQLiteTran; 
SQLiteTran.Action:= caCommitRetaining;  Query.DataBase:= SQLiteConn; 
Error:= EmptyStr;   if DataBaseName = DBName then     DataBaseName:=
ExtractFilePath( ParamStr( 0 ) ) + DBName ;  
SQLiteConn.DatabaseName:= DataBaseName ;   try   
 SQLiteConn.Connected:= True;     Self.Connected:=
SQLiteConn.Connected;   except on E: Exception do begin     Error:=
E.ClassName + LineEnding + E.Message;     Self.Connected:= False; 
end;  end;                            ================


================
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
TSQLiteCache.GetTableNames( var List: Tstrings; ShowSystemTables:
Boolean = False ): Boolean;begin   try   SQLiteConn.GetTableNames(
List, ShowSystemTables );   result:= true  except on E: Exception do
begin     Error:= E.ClassName + LineEnding + E.Message;     Result:=
False;  end;  end;end;    ================

and i call:
==============
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var
ListTableName: Tstrings;begin   ListTableName:= TStrings.Create;   if
not  Cache.GetTableNames( ListTableName ) then      ShowMessage(
Cache.Error );   ==============


And display error:
==============
EAbstractError
Abstract method called
==============

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molly · 2018-02-15 02:17

Quote from: cpalx on February 15, 2018, 03:06:43 amCode: Pascal
 [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var
ListTableName: Tstrings;begin   ListTableName:= TStrings.Create;   if
not  Cache.GetTableNames( ListTableName ) then      ShowMessage(
Cache.Error );   ==============


And display error:
==============
EAbstractError
Abstract method called
==============

Don't create directly from TStrings It is an abstract class. The
warnings during compilation should have given you that hint.

Quote... Warning: Constructing a class "TStrings" with abstract method
"Get"
... Warning: Constructing a class "TStrings" with abstract method
"GetCount"
... Warning: Constructing a class "TStrings" with abstract method
"Clear"
... Warning: Constructing a class "TStrings" with abstract method
"Delete"
... Warning: Constructing a class "TStrings" with abstract method
"Insert"

use:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var
ListTableName: TstringList;begin   ListTableName:=
TStringList.Create;   if not  Cache.GetTableNames( ListTableName )
then      ShowMessage( Cache.Error ); 
more information. TStrings:
QuoteTStrings implements an abstract class to manage an array of
strings. It introduces methods to set and retrieve strings in the
array, searching for a particular string, concatenating the strings
and so on. It also allows an arbitrary object to be associated with
each string.

It also introduces methods to manage a series of name=value settings,
as found in many configuration files.

An instance of TStrings is never created directly, instead a
descendant class such as TStringList should be created. This is
because TStrings is an abstract class which does not implement all
methods; TStrings also doesn't store any strings, this is the
functionality introduced in descendants such as TStringList.

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cpalx · 2018-02-15 02:22

Thanks Molly, problem solved

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molly · 2018-02-15 02:37

You're welcome cpalx.

Another approach is also possible:
Code: [Select]var ListTableName: Tstrings;
begin
  ListTableName:= TStringList.Create;

  if not  Cache.GetTableNames( ListTableName ) then

  ShowMessage( Cache.Error );
end;

In which case you could keep the TStrings var parameter for
TSQLiteCache.GetTableNames. I would personally not opt for it in your
case though as using TStringlist as var parameter makes things more
explicit. btw: classes are passed by reference by default, so no need
for using var modifier.

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cpalx · 2018-02-15 02:46

Thanks for your advice, i changed the params by TStringList