Function in MemoView and OnGetValue problem

Comments

• LurkingKiwi Wellington, New Zealand

  August 2016 edited 1:27AM

  I'm not sure if it's a bug or a feature, but in my GetValue handlers I have to check the VarName parameter for a field I am going to handle, and only change the Value parameter if there is a match.
  As you observe, whole expressions seem to come through OnGetValue recursively, in progressively smaller chunks, until Value is changed by your handler or the expression is resolved by the internal code as it goes around.
  
  Something along the lines of

  ---

  if VarName = 'MyField1' then
  Value := Mydata[Dataset.RecNo].Field1
  else if VarName = 'MyField2' then
  Value := Mydata[Dataset.RecNo].Field2;

  ---

  with something like a list lookup if you are supporting multiple columns or different query results.
  Having a trailing "else Value := 'Error'" in the code above guarantees failure!!
  I'm using it for SQLite query results via a lightweight shim and internally generated tables/lists.
• bob13579

  August 2016 edited August 2016

  LurkingKiwi wrote: »

  ... until Value is changed by your handler or the expression is resolved by the internal code as it goes around.

  
  Good thing you answered. This made me check my OnGetValue Code again. And it turns out that I change the value of the "Value" variable to "Null" if it isn't set.
  
  If I do that then the expression in VarName isn't resolved by the internal code.
  
  You'd think they'd include that in their documentation.
  
  
  Thank you very much.
  
  Edit:
  For other people also getting this problem: If you want to reset the "Value" parameter so the content of "VarName" is resolved internally then set it to "Unassigned":

  Value := Unassigned;