Importing classes
When a formula or a class contains a class name, for example to declare a variable or a plug-in parameter, Ultra Fractal searches for the class in the list of imported files, and then in the current file. To import a file so its classes become available, use the import keyword.
class ExtendedBailout(Test.ufm:Bailout) { public: import "common.ulb" ; ... }
This modified version of the ExtendedBailout example first imports the file Test.ufm because that is where its ancestor is located. Then it imports the plug-in library file common.ulb.
- The import keyword expects a file name within double quotes, without any path information. The file is located using the current formula search paths as set in the Folder tab of the Options dialog.
- If a file name is specified in the ancestor specification of a class, this behaves as if this file was imported before any other files. The browser, however, needs the specification of the ancestor file name here to be able to check the inheritance of classes when selecting plug-in for a plug-in parameter.
- The order in which import statements occur is important. When searching for a class, Ultra Fractal searches the file that was last imported first, and so on. Other than that, import statements can occur anywhere in a formula or class. Even the statements before an import statement are affected by it, because import statements are read and applied before the rest of the code is checked for consistency and type compatibility. For readability, it is recommended to put your import statements at the top of a formula or class.
- Plug-in library files with the .ulb extension have two purposes. When looking for plug-ins for plug-in parameters, the browser will only look in .ulb files. So plug-ins must always be in a plug-in library file. Also, plug-in library files provide a logical place to put classes that are intended to be shared by different fractal formulas, coloring algorithms, and transformations.
- The common.ulb file that is installed with Ultra Fractal provides many useful base classes. See The common.ulb file.
- You can also import classes from .ufm, .ucl, or .uxf files if you have to, but this is recommended only for files that you control yourself. If you are a formula author and you want to provide common functionality to other authors, put them in your own .ulb file. Do not import a class from another author’s .ufm/.ucl/.uxf file because it might be changed in a future revision of that file. See also Publishing your formulas.
Next: The common.ulb file
See Also
Classes
Inheritance
Plug-in parameters