36 lines
1.6 KiB
Python
36 lines
1.6 KiB
Python
# lint-amnesty, pylint: disable=missing-module-docstring
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import copy
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from opaque_keys.edx.locator import DefinitionLocator
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class DefinitionLazyLoader:
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"""
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A placeholder to put into an xblock in place of its definition which
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when accessed knows how to get its content. Only useful if the containing
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object doesn't force access during init but waits until client wants the
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definition. Only works if the modulestore is a split mongo store.
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"""
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def __init__(self, modulestore, course_key, block_type, definition_id, field_converter):
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"""
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Simple placeholder for yet-to-be-fetched data
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:param modulestore: the pymongo db connection with the definitions
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:param definition_locator: the id of the record in the above to fetch
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"""
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self.modulestore = modulestore
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self.course_key = course_key
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self.definition_locator = DefinitionLocator(block_type, definition_id)
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self.field_converter = field_converter
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def fetch(self):
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"""
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Fetch the definition. Note, the caller should replace this lazy
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loader pointer with the result so as not to fetch more than once
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"""
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# get_definition may return a cached value perhaps from another course or code path
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# so, we copy the result here so that updates don't cross-pollinate nor change the cached
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# value in such a way that we can't tell that the definition's been updated.
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definition = self.modulestore.get_definition(self.course_key, self.definition_locator.definition_id)
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return copy.deepcopy(definition)
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