Allow No Selection for ComboBox - what is the value?

Comments

• gordk St.Catherines On. Canada.

  July 2013 edited 2:23PM

  David here is what i use, it might help you,
  when i create the query paramaters i point them to precreated report variables,
  whose values are preset to predetermined values, i modify the variables from either combobox selections
  or radio btn selections, just remember when passing string values to the variabled to
  use extra string delimiters.
• DavidWIII

  July 2013 edited 2:23PM

  Thanks, gordk. I ended up initializing the keyvalues of the comboboxes that are used in the query in the dialogpage onshow event. That seems to be working. I don't know if there are any pitfalls with that approach. I might try using variables as you suggested. I'm not sure what you mean by extra string delimiters but might figure it out once I try it.
• gordk St.Catherines On. Canada.

  July 2013 edited 2:23PM

  David FYI when you create categorized variables in fr if you give them a string value you must
  include the apostrophe string delimiters or the value will be treated as an expression and trigger the
  ogv (ongetvalue)event to try to obtain a value.
• DavidWIII

  July 2013 edited 2:23PM

  gordk
  I know to put single quotes around the value when assigning to a string variable:

  myVariable = 'ZZZ'
  

  I think that is what you are telling me. Please let me know if I'm missing something.
  
  I currently have the keyfields property of each combobox set to a value. The query then uses the keyvalue.
  The params property of each query is:

  DBLookupComboBox1.keyvalue
  

  
  The comboboxes are on a DialogPage. I initialize in the OnShow event. ComboBox1 is alphanumeric. ComboBox2 is numeric.

  procedure DialogPage1OnShow(Sender: TfrxComponent);
  begin
      DBLookupComboBox1.keyvalue := 'ZZZ'; 
      DBLookupComboBox2.keyvalue := 0;           
  end;
  

  
  Please let me know if there is anything wrong with that approach.
  
  I could create variables and pass them to the keyvalues used in the query when the user clicks the OK button on the DialogPage.
  
  Thanks for your replies. I'm still learning.
• gordk St.Catherines On. Canada.

  July 2013 edited 2:23PM

  There really is no best approach, over the years of working with Fr I have found that if something works for you
  go with it.