Re: Cursor Not Passed Properly Inter-Module

On Tue, 28 Nov 2006, Adrian Klaver wrote:

> I think I see what is happening. In your first post dba creates an
> instance of DBtools().CreateDB(). This has a cursor associated with via
> the if statement. The cursor executes the CREATE TABLE statement. In the
> OnSaveMod there is no creation of a DBtools instance. Calling
> DBTools.cur.execute fails because at the top level of the class cur=None.
> With what you have shown cur is only available through the CreateDB
> function.

   And I think that I'm following you. But, I don't see the solution. Here's
more detail.

   In the calling module, modelPage.py, two of the bound (to buttons) methods
are:

   def OnNewMod(self, event):
     newName = functions.newFile(self)
     self.tcName.SetValue(self.appData.projname)
     DBtools().CreateDB(self.appData.dbFileName)

and

   def OnSaveMod(self, event):
     self.modName = self.tcName.GetValue()
     self.modDesc = self.tcDesc.GetValue()
     self.modType = self.rb.GetString(self.rb.GetSelection())
     self.knowlEng = self.keName.GetValue()
     self.method = self.agent.GetSelection()
     DBtools.cur.execute("insert or replace into model (model_name, \
                          model_desc, model_type, \
                          keName, agent) values (self.modnName, \
                          self.modDesc, self.modType, \
                          self.knowlEng, self.method)")
     DBtools().SaveDB(self.appData.dbFileName)

   So, the first is calling a method in the class DBtools, which requires the
cursor, and the second is trying to directly call the cursor.

   Based on your message, I modified dbMethods.py so the connection and
cursor are specified in each method. For example,

   def CreateDB(self, dbFileName):
     self.con = sqlite3.connect(self.appData.dbFileName)
     self.cur = self.con.cursor()

and

   def SaveDB(self, dbFileName):
     self.con = sqlite3.connect(self.appData.dbFileName)
     self.cur = self.con.cursor()
     self.con.commit()

   But, the error shows up on the line before the call to DBtools.SaveDB(). I
read the error message telling me that the calling module does not see the
cursor in the imported module. If that's the case, I have no idea how to
make the cursor visible to the caller. In the class DBtools(), the
connection and cursor cannot be created until the database name is provided.

   Should I put the connection and cursor creation also in config.py with its
configData() class that's imported by all other modules?

Thanks,

Rich



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