Object parameters in Visual FoxPro

A function or form in FoxPro can return a single parameter. Sometimes this is not enough and the traditional response was to store the multiple parameters in an array. Object orientation in Visual FoxPro allows a more flexible approach.

As an example, consider a form which asks the user for a pair of start and end dates. This form must return three parameters. Two are obvious, the start and end dates. The third is more subtle but equally important; we need to know whether the user has entered dates or pressed Cancel. There's a boolean property lSelected for this.

First we need a simple class with properties to hold these three values:

Next, the form needs a property to hold this object. Any value returned by a form has to be retrieved from a property of the form because none of the controls on the form are available at the moment when the form closes and returns its parameter. Code in the form's Init method must put a DateRange object into this form property.

Next, we must put the values from the form into this object. If the user presses the Save button then we store the two dates and .T. in the three properties.

If the user presses Cancel then we store empty dates and .F.

Finally, we put a Return statement in the Unload event of the form.