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Step 8: Walking the Model Tree

In thinking through the design of a model using OpenSCAD, I decided to generate a directory tree where each level contained at lease one SCAD file defining either a single part to be constructed, or an assembly of parts producing something like a wing. To make navigating easy, the directory name will describe the part or assembly, and the SCAD file matching the directory name is the primary design file. Other files may be located next to this design file, but their names will be unique enough to distinguish then from a design file. For example, wing.scad is a design file located in a wing directory. wing_data.scad is an associated data file, and wing_pos.scad defines data used to position parts that make up the wing.

Once this directory organization structure was set, it became obvious that I needed a tool that could navigate the directory tree and provide a way to set a callback* function in each directory visited.

In this section, we will develop the TreeWalker class which will manage navigating the directory tree and providing a way to activate a callback method to perform some action on files in each directory. This class will need to provide a way to specify the root directory for a model, the file extension we are interested in, and the callback method to activate.

Class Constructor

The class constructor will take a single parameter, which is the root path to the model we are going to process. The constructor will verify that the provided path actually points to a directory.

Here is a test that can verify this: tests.test_TreeWalker.test_valid_model_path()

Here is the code that confirms we have a valid directory specified for the constructor model path:

Validating the Model Path

All valid model directories must have at lease one SCAD file, so we will check that in the constructor. Tests should confirm that passing a model path that is not a directory, or a directory that contains mo valid SCAD file will be rejected. All methods should return immediately if the registered model path is None.

Generating File Lists

The class should provide a get_file_list method that returns a list of all files ending with the registered extension. This list will collect all part and assembly files. A second method, get_leaf_file_list, will return only those files in leaf directories (containing no subdirectories). These files are the model parts we need to manufacture to build the model.

Processing Files

Finally, we will provide two routines that actually activate the callback routines: process_files and process_leaf_files.