Create a Loader

Introduction

To write your custom Loader, you will typically subclass the File class, or one of the already existing subclasses that exist in the solidipes-core-plugin package. If the files yous want to load are sequences (e.g. a .gif image sequence), you will also subclass the Sequence class. That will allow you to access sequence specific methods when visualizing the file. If you want to write a loader for data that is not present in the file system, you may directly subclass DataContainer. Here is a diagram that show the hierarchy for some Loaders:

Your custom Loader would typically live in a separate Solidipes plugin package. If the Loader is generic enough (not specific to a particular field), it might be added to the solidipes-core-plugin package. Furthermore, if the Loader enhances the inner workings of Solidipes (e.g. by extending or subclassing DataContainer), it might be added directly in Solidipes to the solidipes.loaders module.

Example

Here is a minimal example of a text Loader that reads the content of a text file on demand:

# Loader class or subclasses can be imported from solidipes or from other plugins
from solidipes.loaders.file import File


class Text(File):
    """Text file"""

    #: List of supported mime types.
    #: The key is the mime type and the value is one or more file extensions (string or list of strings)
    supported_mime_types = {"text/plain": "txt"}

    def __init__(self, **kwargs):
        # Keep the Viewer imports here to avoid circular imports
        from ..viewers.text import Text as TextViewer

        super().__init__(**kwargs)
        # Specify the compatible viewers for this Loader
        self.compatible_viewers[:0] = [TextViewer]

    # Define attributes loaded on demand with the @File.loadable decorator
    # For attributes that must also be cached by solidipes, use the @File.cached_loadable decorator
    @File.loadable
    def text(self):
        text = ""
        with open(self.file_info.path, "r") as f:
            text = f.read()
        return text