docs/src/loaders.txt

================
Template Loaders
================

This part of the documentation explains how to use and write a template loader.

Builtin Loaders
===============

[[list_of_loaders]]

Developing Loaders
==================

Template loaders are just normal Python classes that have to provide some
functions used to load and translate templates. Here is a simple loader implementation
you can use as the base for your own loader:

.. sourcecode:: python

    from os.path import join
    from jinja.parser import Parser
    from jinja.exceptions import TemplateNotFound

    class SimpleLoader(object):
        """
        Slimmed down version of the included `FileSystemLoader`.
        """

        def __init__(self, searchpath):
            self.searchpath = searchpath

        def get_source(self, environment, name, parent):
            """
            The get_source function is unused at the moment. However, future
            versions of jinja will use this function for the debugging
            system. It also works as helper functions for `parse` and
            `load`.
            """
            filename = join(self.searchpath, name)
            if not path.exists(filename):
                raise TemplateNotFound(name)
            f = codecs.open(filename, 'r', environment.template_charset)
            try:
                return f.read()
            finally:
                f.close()

        def parse(self, environment, name, parent):
            """
            Load and parse a template and return the syntax tree.
            """
            source = self.get_source(environment, name, parent)
            return Parser(environment, source, name).parse()

        def load(self, environment, name, translator):
            """
            Parse and translate a template. Currently only translation to
            python code is possible, later Jinja versions however will
            support translating templates to javascript too.
            """
            return translator.process(environment, self.parse(environment, name, None))


.. admonition:: Note

    Once a loader is bound to an environment, you have to omit the environment
    argument for the public functions `get_source`, `parse` and `load`.