[TASK] Introduces UUID-Transformer

hshetl/entities.py

@@ -521,6 +521,7 @@ class Result(object):
         '''Initializes the necessary properties.'''
         self.entity = entity
         self.source = NameResolver(self.entity, 'source', source)()
+        '''source is a Result, NOT a container'''
 
         self.update = EntityList(self.source)
         self.insert = EntityList(self.source)
@@ -571,7 +572,7 @@ class EntityList(list):
     '''
 
     def __init__(self, result):
-        '''Default constructor'''
+        '''Expects a Result instance'''
         self.result = result
         self.source = result.source_container
         self.target = result.target_container

hshetl/transformers.py

@@ -291,3 +291,68 @@ class PropertiesTransformer(AbstractTransformer):
             transformed_properties[prop] = eval('pt.{}.value'.format(operation), globals(), dict(properties.items() + locals().items()))
         return transformed_properties
 
+
+@yamlify
+class UuidTransformer(AbstractTransformer):
+    '''Creates an uuid for entity.
+
+    Applies all operations to the fields in the new data container.
+
+    .. function:: __init__(source[, *args[, **kwargs]])
+
+        Constructor
+
+        :param source: The source container.
+        :param **kwargs: Accepts parameters from :class:`.AbstractTransformer`.
+        :type source: string
+
+    A loader inside of a YAML job definition with more parameters:
+
+    .. code-block:: yaml
+
+       transformer: !uuid
+         entity: !entity
+           id: string
+         source: foobar
+
+    '''
+
+    yaml_tag = u'!uuid'
+
+    def __init__(self, source, uuid_attribute, mapping = {}, *args, **kwargs):
+        super(UuidTransformer, self).__init__(*args, **kwargs)
+        self.source = source
+        self.uuid_attr = uuid_attribute
+        self.mapping = mapping
+        '''The source container to work on.'''
+        if self.entity is not None:
+            self.source = NameResolver(self.entity, 'source', source)()
+
+    def create_container(self):
+        if isinstance(self.source, str) and self.entity is not None:
+            self.source = NameResolver(self.entity, 'source', self.source)()
+        else:
+            raise Exception("Source is of type string and entity is None, so the NameResolver cannot find a correspinding container.")
+        if self.mapping is not {}:
+            mapped_identifiers = [x if x not in self.mapping.keys() else self.mapping[x] for x in self.source.identifiers]
+        self.result = Container(name = self.name,
+                                identifiers = mapped_identifiers,
+                                properties = self.entity.properties)
+        self.entity.add(self.result)
+
+    def can_execute(self):
+        '''Whether the Transformer has everything set needed for its transform operation.'''
+        return self.entity is not None and self.source is not None
+
+    def _execute(self):
+        for record in self.entity.record_repository.itervalues():
+            identifier = record.get_container_identifier(self.source)
+            if identifier is None: continue  # ignore records not known by source.
+            transformed = self._execute_operations(record)
+            record.load(identifier, transformed, self.result)
+
+    def _execute_operations(self, record):
+        properties = record.get_properties(self.source)
+        transformed_properties = properties.copy()
+        transformed_properties[self.uuid_attr] = uuid().hex
+        return transformed_properties
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