Parameter forwards

When you rewrite an existing formula to take advantage of plug-in parameters, this changes the format of parameter sets that are saved while this formula is in use. This means that existing parameter sets cannot be opened anymore. To solve this problem, use parameter forwards.

A parameter forward declares a new parameter name in the formula, and lets it point to a sub-parameter of a plug-in parameter. For example, suppose that an earlier version of the MandelbrotTest example handled its bailout condition itself, with a float parameter named bailout. Now, however, the equivalent parameter is bailout from the bailoutParam plug-in parameter. The following parameter forward expresses this:

  MandelbrotTest {  ; ...  default:    Bailout param bailoutParam      caption = "Bailout Test"    endparam    param bailout = bailoutParam.bailout  }    

A parameter forward starts with the param keyword, the name of the old parameter, the = symbol, and then the “path” to the new parameter, which contains parameter identifiers separated by dots.

In this case, when Ultra Fractal loads an old parameter set, the parameter set will contain the value for a parameter named bailout. Because the formula does not contain a parameter named bailout, Ultra Fractal will search its parameter forwards and will subsequently set the bailout parameter of the class that is the default plug-in for the bailoutParam plug-in parameter (in this case the Bailout class).

For this to work correctly, obviously the default plug-in for the plug-in parameter must be compatible with the previous behavior of the formula. (You can set a default plug-in with the default setting.) This is your responsibility as formula author.

Next: Importing classes

See Also
Plug-in parameters

Parameter forwards