From c71db74efd6089b5ed48203d6cb4684ee7469cb8 Mon Sep 17 00:00:00 2001
From: Wenqi Li <wenqil@nvidia.com>
Date: Sat, 14 Jan 2023 22:06:12 +0000
Subject: [PATCH] reference object method as _target_

Signed-off-by: Wenqi Li <wenqil@nvidia.com>
---
 monai/bundle/config_item.py | 2 +-
 monai/utils/module.py       | 3 +--
 tests/test_config_parser.py | 8 ++++++++
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/monai/bundle/config_item.py b/monai/bundle/config_item.py
index acd664e725c..10fb082ee78 100644
--- a/monai/bundle/config_item.py
+++ b/monai/bundle/config_item.py
@@ -236,7 +236,7 @@ def resolve_module_name(self):
         config = dict(self.get_config())
         target = config.get("_target_")
         if not isinstance(target, str):
-            raise ValueError("must provide a string for the `_target_` of component to instantiate.")
+            return target
 
         module = self.locator.get_component_module_name(target)
         if module is None:
diff --git a/monai/utils/module.py b/monai/utils/module.py
index 1670ecadadc..e5ccdf99923 100644
--- a/monai/utils/module.py
+++ b/monai/utils/module.py
@@ -226,8 +226,7 @@ def instantiate(path: str, **kwargs):
             for `partial` function.
 
     """
-
-    component = locate(path)
+    component = locate(path) if isinstance(path, str) else path
     if component is None:
         raise ModuleNotFoundError(f"Cannot locate class or function path: '{path}'.")
     try:
diff --git a/tests/test_config_parser.py b/tests/test_config_parser.py
index 00945a46ba7..a29780e1bce 100644
--- a/tests/test_config_parser.py
+++ b/tests/test_config_parser.py
@@ -248,6 +248,14 @@ def test_lambda_reference(self):
         result = trans(np.ones(64))
         self.assertTupleEqual(result.shape, (1, 8, 8))
 
+    def test_non_str_target(self):
+        configs = {
+            "forward": {"_target_": "$@model().forward", "x": "$torch.rand(1, 3, 256, 256)"},
+            "model": {"_target_": "monai.networks.nets.resnet.resnet18", "pretrained": False, "spatial_dims": 2},
+        }
+        breakpoint()
+        self.assertisTrue(callable(ConfigParser(config=configs).forward))
+
     def test_error_instance(self):
         config = {"transform": {"_target_": "Compose", "transforms_wrong_key": []}}
         parser = ConfigParser(config=config)