diff --git a/src/store.py b/src/store.py
index 825e554..f008ea0 100644
--- a/src/store.py
+++ b/src/store.py
@@ -3,25 +3,24 @@ import inspect
 import json
 from pathlib import Path
 import pickle
+from typing import Tuple
 
 
-def with_filtered_kwargs(fn):
+def with_filtered_args(fn):
     """
     Return a version of the input function that ignores instead of errors on
-    unknown keyword arguments.
+    unknown arguments.
     """
-    # Enumerate all small_fn's keyword arguments.
-    filter_kwargs = {param.name for param in inspect.signature(fn).parameters.values() 
-                     if param.kind == param.POSITIONAL_OR_KEYWORD 
-                     or param.kind == param.KEYWORD_ONLY}
+    arg_filter = {param.name for param in inspect.signature(fn).parameters.values()
+                  if param.kind == param.POSITIONAL_OR_KEYWORD 
+                  or param.kind == param.KEYWORD_ONLY}
 
     def inner(*args, **kwargs):
         # Filter any keyword arguments not present in small_fn.
-        kwargs = {k: v for k, v in kwargs.items() if k in filter_kwargs}
-
+        kwargs = {k: v for k, v in kwargs.items() if k in arg_filter}
         return fn(*args, **kwargs)
 
-    return inner
+    return inner, arg_filter
 
 
 class load_or_create:
@@ -30,56 +29,160 @@ class load_or_create:
         self,
         load=pickle.load,
         save=pickle.dump,
-        prefix="./",
-        suffix=".pkl",
+        path_fn=lambda hash: hash + ".pkl",
         hash_len=8,
         save_args=False,
         plain_text=False
     ):
-        self.load=with_filtered_kwargs(load)
-        self.save=with_filtered_kwargs(save)
-        self.prefix=prefix
-        self.suffix=suffix
+        self.load=with_filtered_args(load)[0]
+        self.save=with_filtered_args(save)[0]
+        self.path_fn=path_fn
         self.hash_len=hash_len
         self.save_args=save_args
         self.plain_text=plain_text
 
     def __call__(self, fn):
-        # fn_args = tuple(inspect.signature(fn).parameters.keys())
+        return inner(self, fn)
+        
 
-        def inner(*args, **kwargs):
-            # Store the keyword arguments into json and hash it to get the storage path.
-            json_args = (
-                json.dumps(
-                    kwargs,
-                    default=lambda x: vars(x) if hasattr(x, "__dict__") else str(x)
-                ) + "\n"
-            ).encode("utf-8")
-            hash = sha256(json_args, usedforsecurity=False).hexdigest()[:self.hash_len]
-            path = Path(self.prefix + hash + self.suffix)
+class inner(load_or_create):
+    def __init__(self, parent, fn):
+        self.__dict__.update(parent.__dict__)
+        self.fn = fn
+        self.arg_names = [p.name for p in inspect.signature(fn).parameters.values()]
 
-            # Convert all arguments to keyword arguments.
-            # for arg_name, arg in zip(fn_args, args):
-                # kwargs[arg_name] = arg
+    def __call__(self, *args, **kwargs):
+        # Store the keyword arguments into json and hash it to get the storage path.
+        json_args = self.to_json(**kwargs)
+        path = self.path(*args, **kwargs)
+        # path = self.path(hash)
 
-            # If the storage path exists, load the cached object from there.
-            if path.exists():
-                with open(path, "r" if self.plain_text else "rb") as f:
-                   if self.save_args:
-                       f.readline()
-                   return self.load(f, **kwargs)
-
-            # Else, run the function and store its result.
-            out = fn(*args, **kwargs)
-
-            if "/" in self.suffix:
-                path.parent.mkdir(parents=True)
-            with open(path, "w" if self.plain_text else "wb") as f:
+        # If the storage path exists, load the cached object from there.
+        if path.exists():
+            with open(path, "r" if self.plain_text else "rb") as file:
+                # If specified, the first line is a json of the keyword arguments.
                 if self.save_args:
-                    f.write(json_args)
-                self.save(f, out, **kwargs)
+                    file.readline()
+                return self.load(**self.args_to_kwargs(args, kwargs, path=path, file=file))
 
-            return out
+        # Else, run the function. and store its result.
+        obj = self.fn(*args, **kwargs)
 
-        return inner
+        if obj is None:
+            return obj
 
+        path.parent.mkdir(parents=True, exist_ok=True)
+        with open(path, "w" if self.plain_text else "wb") as file:
+            if self.save_args:
+                file.write(json_args)
+            self.save(obj, **self.args_to_kwargs(args, kwargs, path=path, file=file))
+
+        return obj
+
+    def args_to_kwargs(self, args, kwargs, **extra):
+        return extra | kwargs | {self.arg_names[i]: a for i, a in enumerate(args)}
+
+    def to_json(self, **kwargs) -> bytes:
+        """Serialize all keyword arguments to json. 
+        We never serialize positional arguments"""
+        return (
+            json.dumps(
+                kwargs,
+                default=lambda x: vars(x) if hasattr(x, "__dict__") else str(x)
+            ) + "\n"
+        ).encode("utf-8")
+
+    def make_hash(self, **kwargs):
+        """Serialize all keyword arguments to json and hash it."""
+        json_args = self.to_json(**kwargs)
+        hash_str = sha256(json_args, usedforsecurity=False).hexdigest()
+        return hash_str[:self.hash_len]
+
+    def path_and_hash(self, *args, **kwargs) -> Tuple[Path, str]:
+        path_fn, arg_filter = with_filtered_args(self.path_fn)
+
+        hash = self.make_hash(
+            # Do not have arguments in the hash that path_fn uses.
+            **{k: a for k, a in kwargs.items() if k not in arg_filter}
+        )
+
+        path_args = self.args_to_kwargs(args, kwargs, hash=hash)
+
+        path = Path(path_fn(**path_args))
+
+        return path, hash
+
+    def hash(self, *args, **kwargs) -> str:
+        """Hash the keyword arguments.
+        Note that the hash is dependent on the path function of this instance:
+        All arguments of the path function are excluded from the hash."""
+        return self.path_and_hash(*args, **kwargs)[1]
+
+    def path(self, *args, **kwargs) -> Path:
+        return self.path_and_hash(*args, **kwargs)[0]
+
+    def dir(self, *args, **kwargs) -> Path:
+        return self.path(*args, **kwargs).parent
+
+
+#%% [markdown]
+# A big possible extension is to hash the returned object.
+# If we do that, we can do something like this:
+# ```
+# fn = load_or_create(orig_fn)
+# obj = fn(*args)
+# assert fn.path(*args) == fn.obj_path(obj)
+# ```
+# 
+# So, we'd get a _path_ from an object!
+#
+# How would this work out?
+# 
+# first, after loading and/or storing, we save the hash as we store the object.
+# ```
+# obj_hash = get_hash_from_flie(path)
+# self.cache[obj_hash] = [path, kwargs]
+# ```
+# 
+# then, in self.obj_path, we fake-save the object using the provided save function.
+# instead of saving to a file, we save to some class that inherited io.BytesIO:
+# ```
+# class HashingWriter(io.BytesIO):
+#     def __init__(self):
+#         super().__init__()  # Initialize the BytesIO buffer
+#         self.hash = hashlib.sha256()  # Initialize the SHA-256 hash object
+# 
+#     def write(self, b):
+#         return self.hash.update(b)  # Update the hash with the data being written
+# 
+#     def get_hash(self):
+#         return self.hash.hexdigest()  # Return the hexadecimal digest of the hash
+# ```
+#
+# so self.obj_path would look something like:
+# ```
+# def obj_path(self, obj):
+#     with open(HashingWriter(), "wb") as f:
+#         f.write(obj)
+#         if f.get_hash() in self.cache:
+#             return self.cache[hash][0]
+# ```
+# In reality, obj_path() can just be part of path(), since path() should expect
+# kwargs to be present and can safely assume it's being called as obj_path() 
+# otherwise.
+#
+# Caveat, this will only work for save functions that use an open file.
+# Save functions that take a path would not work.
+#
+# More practical case:
+# ```
+# fn_a = load_or_create()(fn_a)
+#
+# def fn_b(obj_a, cfg):
+#     do_something(obj_a, cfg)
+#
+# fn_b = load_or_create(
+#     path_fn=lambda obj_a, hash: fn_a.get_path(obj_a) / hash
+# )(fn_b)
+# ```
+# This avoids having to make pass obj_a's config to fn_b in order to determine the path!