Add Pointer field

src/grung/types.py

@@ -95,32 +95,51 @@ class Record(Dict[(str, Field)]):
         return f"{self.__class__.__name__}[{self.doc_id}]: {self.items()}"
 
 
+@dataclass
+class Pointer(Field):
+    """
+    Store a string reference to a record.
+    """
+
+    name: str = ""
+    value_type: type = Record
+
+    def serialize(self, value: value_type, db: TinyDB) -> str:
+        if value:
+            if not value.doc_id:
+                raise PointerReferenceError(value)
+            return f"{value._metadata.table}::{value.uid}"
+        return ""
+
+    def deserialize(self, value: str, db: TinyDB, recurse=True) -> value_type:
+        pt, puid = value.split("::")
+        if puid:
+            return db.table(pt).search(where("uid") == puid, recurse=recurse)[0]
+        return value
+
+
 @dataclass
 class Collection(Field):
     """
-    A collection of fields that store pointers instead of dicts.
+    A collection of pointers.
     """
 
     value_type: type = Record
     default: List[value_type] = field(default_factory=lambda: [])
 
-    def serialize(self, value: value_type, db: TinyDB) -> List[str]:
-        vals = self.default
-        if value:
-            for rec in value:
-                if not rec.doc_id:
-                    raise PointerReferenceError(rec)
-                vals.append(f"{rec._metadata.table}::{rec.uid}")
-        return vals
+    def _pointer(self, rec):
+        return Pointer(value_type=type(rec))
 
-    def deserialize(self, rec: List[value_type], db: TinyDB, recurse=True) -> value_type:
+    def serialize(self, values: List[Record], db: TinyDB) -> List[str]:
+        if values:
+            return [self._pointer(val).serialize(val, db=db) for val in values]
+
+    def deserialize(self, values: List[str], db: TinyDB, recurse=True) -> List[value_type]:
         """
         Recursively deserialize the objects in this collection
         """
-        vals = []
         if not recurse:
-            return rec
-        for member in rec:
-            pt, puid = member.split("::")
-            vals.append(db.table(pt).search(where("uid") == puid)[0])
-        return vals
+            return values
+        if values:
+            return [self._pointer(val).deserialize(val, db=db, recurse=recurse) for val in values]
+        return []