Transformer: BlockCountsTransformer

lms/djangoapps/course_api/blocks/transformers/block_counts.py

+"""
+Block Counts Transformer
+"""
+from openedx.core.lib.block_cache.transformer import BlockStructureTransformer
+
+
+class BlockCountsTransformer(BlockStructureTransformer):
+    """
+    Keep a count of descendant blocks of the requested types
+    """
+    VERSION = 1
+    BLOCK_COUNTS = 'block_counts'
+
+    def __init__(self, block_types_to_count):
+        self.block_types_to_count = block_types_to_count
+
+    @classmethod
+    def name(cls):
+        return "blocks_api:block_counts"
+
+    @classmethod
+    def collect(cls, block_structure):
+        """
+        Collects any information that's necessary to execute this transformer's
+        transform method.
+        """
+        # collect basic xblock fields
+        block_structure.request_xblock_fields('category')
+
+    def transform(self, usage_info, block_structure):  # pylint: disable=unused-argument
+        """
+        Mutates block_structure based on the given usage_info.
+        """
+        if not self.block_types_to_count:
+            return
+
+        for block_key in block_structure.post_order_traversal():
+            for block_type in self.block_types_to_count:
+                descendants_type_count = sum([
+                    block_structure.get_transformer_block_field(child_key, self, block_type, 0)
+                    for child_key in block_structure.get_children(block_key)
+                ])
+                block_structure.set_transformer_block_field(
+                    block_key,
+                    self,
+                    block_type,
+                    (
+                        descendants_type_count +
+                        (1 if (block_structure.get_xblock_field(block_key, 'category') == block_type) else 0)
+                    )
+                )

lms/djangoapps/course_api/blocks/transformers/tests/test_block_counts.py

+"""
+Tests for BlockCountsTransformer.
+"""
+
+# pylint: disable=protected-access
+from openedx.core.lib.block_cache.block_structure_factory import BlockStructureFactory
+from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
+from xmodule.modulestore.tests.factories import SampleCourseFactory
+
+from ..block_counts import BlockCountsTransformer
+
+
+class TestBlockCountsTransformer(ModuleStoreTestCase):
+    """
+    Test behavior of BlockCountsTransformer
+    """
+    def setUp(self):
+        super(TestBlockCountsTransformer, self).setUp()
+        self.course_key = SampleCourseFactory.create().id
+        self.course_usage_key = self.store.make_course_usage_key(self.course_key)
+        self.block_structure = BlockStructureFactory.create_from_modulestore(self.course_usage_key, self.store)
+
+    def test_transform(self):
+        # collect phase
+        BlockCountsTransformer.collect(self.block_structure)
+        self.block_structure._collect_requested_xblock_fields()
+
+        # transform phase
+        BlockCountsTransformer(['problem', 'chapter']).transform(usage_info=None, block_structure=self.block_structure)
+
+        # block_counts
+        chapter_x_key = self.course_key.make_usage_key('chapter', 'chapter_x')
+        block_counts_for_chapter_x = self.block_structure.get_transformer_block_data(
+            chapter_x_key, BlockCountsTransformer,
+        )
+        block_counts_for_course = self.block_structure.get_transformer_block_data(
+            self.course_usage_key, BlockCountsTransformer,
+        )
+
+        # verify count of chapters
+        self.assertEquals(block_counts_for_course['chapter'], 2)
+
+        # verify count of problems
+        self.assertEquals(block_counts_for_course['problem'], 6)
+        self.assertEquals(block_counts_for_chapter_x['problem'], 3)
+
+        # verify other block types are not counted
+        for block_type in ['course', 'html', 'video']:
+            self.assertNotIn(block_type, block_counts_for_course)
+            self.assertNotIn(block_type, block_counts_for_chapter_x)