diff --git a/README.md b/README.md
index 6074325..544d9d7 100644
--- a/README.md
+++ b/README.md
@@ -93,7 +93,7 @@ $ python -m oneface.wrap_cli run add.yaml qt_gui  # run Qt GUI app
 + Generate CLI, Qt GUI, Dash Web app from a python function or a command line.
 + Automatically check the type and range of input parameters and pretty print them.
 + Easy extension of parameter types and GUI widgets.
-+ Support for embedding the generated interface into a parent application
++ Support for embedding the generated interface into a parent application.
 
 Detail usage see the [documentation](https://oneface.readthedocs.io/en/latest/).
 
diff --git a/docs/index.md b/docs/index.md
index 1b955c5..1943081 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -7,7 +7,7 @@ oneFace is a Python library for automatically generating multiple interfaces(CLI
 + Generate CLI, Qt GUI, Dash Web app from a python function or a command line.
 + Automatically check the type and range of input parameters and pretty print them.
 + Easy extension of parameter types and GUI widgets.
-+ Support for embedding the generated interface into a parent application
++ Support for embedding the generated interface into a parent application.
 
 
 ## Installation
diff --git a/oneface/__init__.py b/oneface/__init__.py
index 83b05c0..63e29e2 100644
--- a/oneface/__init__.py
+++ b/oneface/__init__.py
@@ -1,5 +1,6 @@
-from .core import one, Arg
+from .core import one
+from .arg import Arg
 
-__version__ = '0.1.8'
+__version__ = '0.1.9'
 
 __all__ = [one, Arg]
diff --git a/oneface/arg.py b/oneface/arg.py
index e974cb3..b9d1a8e 100644
--- a/oneface/arg.py
+++ b/oneface/arg.py
@@ -69,7 +69,7 @@ def _check_number_in_range(v, range):
 Arg.register_type_check(bool)
 
 
-def get_func_argobjs(func: T.Callable) -> T.OrderedDict[str, Arg]:
+def parse_func_args(func: T.Callable) -> T.OrderedDict[str, Arg]:
     args = OrderedDict()
     sig = inspect.signature(func)
     for n, p in sig.parameters.items():
diff --git a/oneface/check.py b/oneface/check.py
new file mode 100644
index 0000000..5644dfa
--- /dev/null
+++ b/oneface/check.py
@@ -0,0 +1,116 @@
+import typing as T
+from copy import copy
+from ctypes import ArgumentError
+import functools
+
+from rich.console import Console
+from rich.table import Table
+
+from .arg import Empty, Arg, parse_func_args
+from .utils import AllowWrapInstanceMethod
+
+
+def check_args(func=None, **kwargs):
+    if func is None:
+        return functools.partial(check_args, **kwargs)
+    return CallWithCheck(func, **kwargs)
+
+
+console = Console()
+
+
+class ArgsCheckError(Exception):
+    pass
+
+
+def parse_pass_in(
+        args: tuple, kwargs: dict,
+        arg_objs: T.OrderedDict[str, "Arg"]):
+    """Get the pass in value of the func
+    arguments according to it's signature."""
+    args_ = list(args)
+    kwargs = copy(kwargs)
+    res = {}
+    for n, a in arg_objs.items():
+        has_default = a.default is not Empty
+        if len(args_) > 0:
+            res[n] = args_.pop(0)
+        elif (len(kwargs) > 0) and (n in kwargs):
+            res[n] = kwargs.pop(n)
+        else:
+            if has_default:
+                res[n] = a.default
+            else:
+                raise ArgumentError(
+                    f"{n} is not provided and has no default value.")
+    return res
+
+
+class CallWithCheck(AllowWrapInstanceMethod):
+    def __init__(self, func, print_args=True, name=None):
+        self.func = func
+        functools.update_wrapper(self, func)
+        if name is not None:
+            self.name = name
+        elif hasattr(func, "name"):
+            self.name = func.name
+        else:
+            self.name = func.__name__
+        self.is_print_args = print_args
+        self.table = None
+
+    def __call__(self, *args, **kwargs):
+        arg_objs = parse_func_args(self.func)
+        if self.is_print_args:
+            self.table = self.get_argument_table()
+        # check args
+        vals = parse_pass_in(args, kwargs, arg_objs)
+        errors = []
+        for n, arg in arg_objs.items():
+            self._check_arg(n, arg, vals[n], errors)
+        if self.is_print_args:
+            self.print_args()
+        if len(errors) > 0:
+            raise ArgsCheckError(errors)
+        return self.func(*args, **kwargs)
+
+    def print_args(self):
+        if self.name:
+            console.print(f"Run: [bold purple]{self.name}")
+        console.print("Arguments table:\n")
+        console.print(self.table)
+        console.print()
+
+    def _check_arg(
+            self, name: str, arg: Arg,
+            val: T.Any, errors: T.List[Exception]):
+        val_str = str(val)
+        range_str = str(arg.range)
+        tp_str = str(type(val))
+        ann_tp_str = str(arg.type)
+        try:
+            arg.check(val)
+        except Exception as e:
+            errors.append(e)
+            if isinstance(e, ValueError):
+                val_str = f"[red]{val_str}[/red]"
+                range_str = f"[red]{range_str}[/red]"
+            elif isinstance(e, TypeError):
+                ann_tp_str = f"[red]{ann_tp_str}[/red]"
+                tp_str = f"[red]{tp_str}[/red]"
+            else:
+                raise e
+        if self.is_print_args:
+            self.table.add_row(name, ann_tp_str, range_str, val_str, tp_str)
+
+    @staticmethod
+    def get_argument_table():
+        table = Table(
+            show_header=True, header_style="bold magenta",
+            box=None)
+        table.add_column("Argument")
+        table.add_column("Type")
+        table.add_column("Range")
+        table.add_column("InputVal")
+        table.add_column("InputType")
+        return table
diff --git a/oneface/core.py b/oneface/core.py
index 1f845c0..b95fd17 100644
--- a/oneface/core.py
+++ b/oneface/core.py
@@ -1,43 +1,6 @@
-import typing as T
-from copy import copy
-from ctypes import ArgumentError
 import functools
 
-from rich.console import Console
-from rich.table import Table
-
-
-from .arg import Empty, Arg, get_func_argobjs
-
-
-console = Console()
-
-
-class ArgsCheckError(Exception):
-    pass
-
-
-def parse_pass_in(
-        args: tuple, kwargs: dict,
-        arg_objs: T.OrderedDict[str, "Arg"]):
-    """Get the pass in value of the func
-    arguments according to it's signature."""
-    args_ = list(args)
-    kwargs = copy(kwargs)
-    res = {}
-    for n, a in arg_objs.items():
-        has_default = a.default is not Empty
-        if len(args_) > 0:
-            res[n] = args_.pop(0)
-        elif (len(kwargs) > 0) and (n in kwargs):
-            res[n] = kwargs.pop(n)
-        else:
-            if has_default:
-                res[n] = a.default
-            else:
-                raise ArgumentError(
-                    f"{n} is not provided and has no default value.")
-    return res
+from .check import CallWithCheck
 
 
 def one(func=None, **kwargs):
@@ -46,79 +9,7 @@ def one(func=None, **kwargs):
     return One(func, **kwargs)
 
 
-class One(object):
-    def __init__(self, func, print_args=True, name=None):
-        self.func = func
-        functools.update_wrapper(self, func)
-        self.arg_objs = get_func_argobjs(func)
-        if name is not None:
-            self.name = name
-        elif hasattr(func, "name"):
-            self.name = func.name
-        else:
-            self.name = func.__name__
-        self.is_print_args = print_args
-        self.table = None
-
-    def __call__(self, *args, **kwargs):
-        if self.is_print_args:
-            self.table = self.get_argument_table()
-        # check args
-        vals = parse_pass_in(args, kwargs, self.arg_objs)
-        errors = []
-        for n, arg in self.arg_objs.items():
-            self._check_arg(n, arg, vals[n], errors)
-        if self.is_print_args:
-            self.print_args()
-        if len(errors) > 0:
-            raise ArgsCheckError(errors)
-        return self.func(*args, **kwargs)
-
-    def print_args(self):
-        if self.name:
-            console.print(f"Run: [bold purple]{self.name}")
-        console.print("Arguments table:\n")
-        console.print(self.table)
-        console.print()
-
-    def __get__(self, obj, objtype):
-        """Support instance method
-        see https://stackoverflow.com/a/3296318/8500469"""
-        return functools.partial(self.__call__, obj)
-
-    def _check_arg(
-            self, name: str, arg: Arg,
-            val: T.Any, errors: T.List[Exception]):
-        val_str = str(val)
-        range_str = str(arg.range)
-        tp_str = str(type(val))
-        ann_tp_str = str(arg.type)
-        try:
-            arg.check(val)
-        except Exception as e:
-            errors.append(e)
-            if isinstance(e, ValueError):
-                val_str = f"[red]{val_str}[/red]"
-                range_str = f"[red]{range_str}[/red]"
-            elif isinstance(e, TypeError):
-                ann_tp_str = f"[red]{ann_tp_str}[/red]"
-                tp_str = f"[red]{tp_str}[/red]"
-            else:
-                raise e
-        if self.is_print_args:
-            self.table.add_row(name, ann_tp_str, range_str, val_str, tp_str)
-
-    @staticmethod
-    def get_argument_table():
-        table = Table(
-            show_header=True, header_style="bold magenta",
-            box=None)
-        table.add_column("Argument")
-        table.add_column("Type")
-        table.add_column("Range")
-        table.add_column("InputVal")
-        table.add_column("InputType")
-        return table
+class One(CallWithCheck):
 
     def cli(self):
         from fire import Fire
diff --git a/oneface/dash_app/app.py b/oneface/dash_app/app.py
index 389cf63..1e779b5 100644
--- a/oneface/dash_app/app.py
+++ b/oneface/dash_app/app.py
@@ -8,14 +8,15 @@
 import visdcc
 
 from ..types import (Selection, SubSet, InputPath, OutputPath)
-from ..arg import Empty, get_func_argobjs
+from ..arg import Empty, parse_func_args
 from .input_item import (
     InputItem, IntInputItem, FloatInputItem, StrInputItem, BoolInputItem,
     DropdownInputItem, MultiDropdownInputItem,
 )
+from ..utils import AllowWrapInstanceMethod
 
 
-class App(object):
+class App(AllowWrapInstanceMethod):
     type_to_widget_constructor: T.Dict[str, "InputItem"] = {}
     convert_types: T.Dict[str, T.Callable] = {}
 
@@ -113,7 +114,7 @@ def parse_args(self) -> T.List["html.Div"]:
         """Parse target function's arguments,
         return a list of input widgets."""
         widgets, names, types, attrs = [], [], [], []
-        arg_objs = get_func_argobjs(self.func)
+        arg_objs = parse_func_args(self.func)
         for n, a in arg_objs.items():
             if a.type is Empty:
                 continue
diff --git a/oneface/qt.py b/oneface/qt.py
index 3ba0c3e..c57a3ec 100644
--- a/oneface/qt.py
+++ b/oneface/qt.py
@@ -4,7 +4,8 @@
 from qtpy import QtCore
 
 from .types import (InputPath, OutputPath, Selection, SubSet)
-from .arg import Empty, get_func_argobjs
+from .arg import Empty, parse_func_args
+from .utils import AllowWrapInstanceMethod
 
 
 class Worker(QtCore.QObject):
@@ -34,7 +35,7 @@ def get_app():
     return app
 
 
-class GUI():
+class GUI(AllowWrapInstanceMethod):
 
     type_to_widget_constructor = {}
 
@@ -71,7 +72,7 @@ def compose_ui(self):
         self.window.setLayout(self.layout)
 
     def compose_arg_widgets(self, layout: QtWidgets.QVBoxLayout):
-        arg_objs = get_func_argobjs(self.func)
+        arg_objs = parse_func_args(self.func)
         for n, a in arg_objs.items():
             if a.type is Empty:
                 continue
diff --git a/oneface/types.py b/oneface/types.py
index 1f4ba8b..25ba313 100644
--- a/oneface/types.py
+++ b/oneface/types.py
@@ -1,6 +1,6 @@
 from pathlib import Path
 
-from oneface.core import Arg
+from oneface.arg import Arg
 
 
 class ArgType(object):
diff --git a/oneface/utils.py b/oneface/utils.py
new file mode 100644
index 0000000..54d97f9
--- /dev/null
+++ b/oneface/utils.py
@@ -0,0 +1,11 @@
+import functools
+
+
+class AllowWrapInstanceMethod(object):
+    def __get__(self, obj, objtype):
+        if not hasattr(self, "_bounded"):  # bound only once
+            target_func = self.func
+            bound_mth = functools.partial(target_func, obj)
+            self.func = bound_mth
+            self._bounded = True
+        return self
diff --git a/oneface/wrap_cli/wrap.py b/oneface/wrap_cli/wrap.py
index 8a66977..52f402b 100644
--- a/oneface/wrap_cli/wrap.py
+++ b/oneface/wrap_cli/wrap.py
@@ -12,7 +12,7 @@
 import yaml
 
 from ..arg import Arg, Empty
-from ..core import parse_pass_in
+from ..check import parse_pass_in
 
 
 def load_config(path: str) -> dict:
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 7b60add..17bde8e 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -2,6 +2,7 @@
 sys.path.insert(0, "./")
 import subprocess
 from oneface.core import *
+from oneface.arg import Arg
 import pytest
 
 
diff --git a/tests/test_core.py b/tests/test_core.py
index db88b89..67f3d2b 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1,10 +1,11 @@
 from oneface.core import *
+from oneface.check import *
 
 import pytest
 
 
 def test_arg_check():
-    @one(print_args=False)
+    @check_args(print_args=False)
     def func(a: Arg(int, [0, 10]), b: Arg(float, [0, 1]), k=10):
         return a
     assert func(10, 0.3) == 10
@@ -25,12 +26,12 @@ def func(a: Arg(int, [0, 10]), b: Arg(float, [0, 1]), k=10):
     assert isinstance(e.value.args[0][0], ValueError)
     assert isinstance(e.value.args[0][1], TypeError)
     func(2, 0.5)
-    @one(print_args=False)
+    @check_args(print_args=False)
     def func(a: Arg(bool)):
         pass
     with pytest.raises(ArgsCheckError) as e:
         func(1)
-    @one(print_args=False)
+    @check_args(print_args=False)
     def func(a: Arg(int)):
         return a
     with pytest.raises(ArgsCheckError) as e:
@@ -67,7 +68,7 @@ class A():
         def __init__(self, a):
             self.a = a
         
-        @one(print_args=False)
+        @check_args(print_args=False)
         def mth1(self, b: Arg(float, [0, 1])):
             return self.a + b
 
@@ -85,7 +86,7 @@ def mth1(self, b: Arg(float, [0, 1])):
 def test_parse_pass_in():
     def f1(a, b, c=1, d=2):
         pass
-    arg_objs = get_func_argobjs(f1)
+    arg_objs = parse_func_args(f1)
     vals = parse_pass_in((1, 2), {'d': 10}, arg_objs)
     assert (vals['a'] == 1) and (vals['b'] == 2) and (vals['c'] == 1) and (vals['d'] == 10)
     vals = parse_pass_in((1, 2, 3), {}, arg_objs)
diff --git a/tests/test_dash.py b/tests/test_dash.py
index 7d0d0b3..2aef69e 100644
--- a/tests/test_dash.py
+++ b/tests/test_dash.py
@@ -1,5 +1,6 @@
 from oneface.dash_app import *
-from oneface.core import one, Arg
+from oneface.core import one
+from oneface.arg import Arg
 from oneface.dash_app.embed import flask_route
 
 from dash import dcc
@@ -68,4 +69,23 @@ def test_embed():
     @one
     def func(name: str):
         return name
-    
\ No newline at end of file
+    
+
+def test_on_native_func():
+    @app
+    def func(a: int, b: float):
+        return a + b
+
+    assert func.get_dash_app() is not None
+    assert func.input_names == ['a', 'b']
+    assert func.input_types == [int, float]
+
+    class A():
+        @app
+        def mth1(self, name: str, weight: float):
+            return name, weight
+    
+    a = A()
+    assert a.mth1.get_dash_app() is not None
+    assert a.mth1.input_names == ['name', 'weight']
+    assert a.mth1.input_types == [str, float]
diff --git a/tests/test_qt.py b/tests/test_qt.py
index fc7b6eb..582ca0a 100644
--- a/tests/test_qt.py
+++ b/tests/test_qt.py
@@ -1,5 +1,6 @@
 import sys; sys.path.insert(0, "./")
 from oneface.core import *
+from oneface.check import *
 from oneface.qt import *
 
 import pytest
@@ -23,7 +24,7 @@ def test_int_with_default():
     @one
     def func(a: Arg(int, [0, 10]) = 1):
         return a
-    
+
     assert isinstance(func, GUI)
     kwargs = func.get_args()
     assert kwargs['a'] == 1
@@ -120,5 +121,21 @@ def func(a: Arg(InputPath) = "a"):
     assert isinstance(e.value.args[0][0], ValueError)
 
 
+def test_on_native_func():
+    @gui
+    def func(a: int, b: float):
+        return a + b
+
+    assert isinstance(func, GUI)
+
+    class A():
+        @gui
+        def mth1(self, name: str, weight: float):
+            return name, weight
+
+    a = A()
+    assert isinstance(a.mth1, GUI)
+
+
 if __name__ == "__main__":
     test_set_text()
diff --git a/tests/test_types.py b/tests/test_types.py
index f5db24c..a552b67 100644
--- a/tests/test_types.py
+++ b/tests/test_types.py
@@ -1,5 +1,6 @@
 from oneface.types import *
-from oneface.core import one, Arg, ArgsCheckError
+from oneface.core import one
+from oneface.check import Arg, ArgsCheckError
 
 import pytest