Move common object functions into object_api mixin

include/pybind11/attr.h

@@ -276,7 +276,7 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 
 /// Process a parent class attribute
 template <typename T>
-struct process_attribute<T, enable_if_t<std::is_base_of<handle, T>::value>> : process_attribute_default<handle> {
+struct process_attribute<T, enable_if_t<is_pyobject<T>::value>> : process_attribute_default<handle> {
     static void init(const handle &h, type_record *r) { r->bases.append(h); }
 };
 

include/pybind11/cast.h

@@ -908,7 +908,7 @@ template <> struct handle_type_name<args> { static PYBIND11_DESCR name() { retur
 template <> struct handle_type_name<kwargs> { static PYBIND11_DESCR name() { return _("**kwargs"); } };
 
 template <typename type>
-struct type_caster<type, enable_if_t<std::is_base_of<handle, type>::value>> {
+struct type_caster<type, enable_if_t<is_pyobject<type>::value>> {
 public:
     template <typename T = type, enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) { value = type(src); return value.check(); }
@@ -1296,18 +1296,20 @@ unpacking_collector<policy> collect_arguments(Args &&...args) {
     return { std::forward<Args>(args)... };
 }
 
-NAMESPACE_END(detail)
-
+template <typename Derived>
 template <return_value_policy policy, typename... Args>
-object handle::operator()(Args &&...args) const {
-    return detail::collect_arguments<policy>(std::forward<Args>(args)...).call(m_ptr);
+object object_api<Derived>::operator()(Args &&...args) const {
+    return detail::collect_arguments<policy>(std::forward<Args>(args)...).call(derived().ptr());
 }
 
-template <return_value_policy policy,
-          typename... Args> object handle::call(Args &&... args) const {
+template <typename Derived>
+template <return_value_policy policy, typename... Args>
+object object_api<Derived>::call(Args &&...args) const {
     return operator()<policy>(std::forward<Args>(args)...);
 }
 
+NAMESPACE_END(detail)
+
 #define PYBIND11_MAKE_OPAQUE(Type) \
     namespace pybind11 { namespace detail { \
         template<> class type_caster<Type> : public type_caster_base<Type> { }; \

include/pybind11/pytypes.h

@@ -16,50 +16,72 @@
 NAMESPACE_BEGIN(pybind11)
 
 /* A few forward declarations */
-class object; class str; class iterator;
+class handle; class object;
+class str; class iterator;
 struct arg; struct arg_v;
-namespace detail { class accessor; class args_proxy; class kwargs_proxy; }
+
+NAMESPACE_BEGIN(detail)
+class accessor; class args_proxy;
+
+/// Tag and check to identify a class which implements the Python object API
+class pyobject_tag { };
+template <typename T> using is_pyobject = std::is_base_of<pyobject_tag, T>;
+
+/// Mixin which adds common functions to handle, object and various accessors.
+/// The only requirement for `Derived` is to implement `PyObject *Derived::ptr() const`.
+template <typename Derived>
+class object_api : public pyobject_tag {
+    const Derived &derived() const { return static_cast<const Derived &>(*this); }
+
+public:
+    iterator begin() const;
+    iterator end() const;
+    accessor operator[](handle key) const;
+    accessor operator[](const char *key) const;
+    accessor attr(handle key) const;
+    accessor attr(const char *key) const;
+    args_proxy operator*() const;
+
+    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    object operator()(Args &&...args) const;
+    template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
+    PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
+        object call(Args&&... args) const;
+
+    bool is_none() const { return derived().ptr() == Py_None; }
+    pybind11::str str() const;
+    pybind11::str repr() const;
+
+    int ref_count() const { return static_cast<int>(Py_REFCNT(derived().ptr())); }
+    handle get_type() const;
+};
+
+NAMESPACE_END(detail)
 
 /// Holds a reference to a Python object (no reference counting)
-class handle {
+class handle : public detail::object_api<handle> {
 public:
-    handle() : m_ptr(nullptr) { }
-    handle(const handle &other) : m_ptr(other.m_ptr) { }
+    handle() = default;
     handle(PyObject *ptr) : m_ptr(ptr) { }
+
     PyObject *ptr() const { return m_ptr; }
     PyObject *&ptr() { return m_ptr; }
     const handle& inc_ref() const { Py_XINCREF(m_ptr); return *this; }
     const handle& dec_ref() const { Py_XDECREF(m_ptr); return *this; }
-    int ref_count() const { return (int) Py_REFCNT(m_ptr); }
-    handle get_type() const { return handle((PyObject *) Py_TYPE(m_ptr)); }
-    inline iterator begin() const;
-    inline iterator end() const;
-    inline detail::accessor operator[](handle key) const;
-    inline detail::accessor operator[](const char *key) const;
-    inline detail::accessor attr(handle key) const;
-    inline detail::accessor attr(const char *key) const;
-    inline pybind11::str str() const;
-    inline pybind11::str repr() const;
-    bool is_none() const { return m_ptr == Py_None; }
+
     template <typename T> T cast() const;
-    template <return_value_policy policy = return_value_policy::automatic_reference, typename ... Args>
-    PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
-        object call(Args&&... args) const;
-    template <return_value_policy policy = return_value_policy::automatic_reference, typename ... Args>
-    object operator()(Args&&... args) const;
     operator bool() const { return m_ptr != nullptr; }
     bool operator==(const handle &h) const { return m_ptr == h.m_ptr; }
     bool operator!=(const handle &h) const { return m_ptr != h.m_ptr; }
     bool check() const { return m_ptr != nullptr; }
-    inline detail::args_proxy operator*() const;
 protected:
-    PyObject *m_ptr;
+    PyObject *m_ptr = nullptr;
 };
 
 /// Holds a reference to a Python object (with reference counting)
 class object : public handle {
 public:
-    object() { }
+    object() = default;
     object(const object &o) : handle(o) { inc_ref(); }
     object(const handle &h, bool borrowed) : handle(h) { if (borrowed) inc_ref(); }
     object(PyObject *ptr, bool borrowed) : handle(ptr) { if (borrowed) inc_ref(); }
@@ -347,14 +369,6 @@ public:
     PYBIND11_OBJECT_DEFAULT(iterable, object, detail::PyIterable_Check)
 };
 
-inline detail::accessor handle::operator[](handle key) const { return detail::accessor(*this, key, false); }
-inline detail::accessor handle::operator[](const char *key) const { return detail::accessor(*this, key, false); }
-inline detail::accessor handle::attr(handle key) const { return detail::accessor(*this, key, true); }
-inline detail::accessor handle::attr(const char *key) const { return detail::accessor(*this, key, true); }
-inline iterator handle::begin() const { return iterator(PyObject_GetIter(ptr()), false); }
-inline iterator handle::end() const { return iterator(nullptr, false); }
-inline detail::args_proxy handle::operator*() const { return detail::args_proxy(*this); }
-
 class bytes;
 
 class str : public object {
@@ -400,24 +414,6 @@ inline namespace literals {
 inline str operator"" _s(const char *s, size_t size) { return {s, size}; }
 }
 
-inline pybind11::str handle::str() const {
-    PyObject *strValue = PyObject_Str(m_ptr);
-#if PY_MAJOR_VERSION < 3
-    PyObject *unicode = PyUnicode_FromEncodedObject(strValue, "utf-8", nullptr);
-    Py_XDECREF(strValue); strValue = unicode;
-#endif
-    return pybind11::str(strValue, false);
-}
-
-inline pybind11::str handle::repr() const {
-    PyObject *strValue = PyObject_Repr(m_ptr);
-#if PY_MAJOR_VERSION < 3
-    PyObject *unicode = PyUnicode_FromEncodedObject(strValue, "utf-8", nullptr);
-    Py_XDECREF(strValue); strValue = unicode;
-#endif
-    return pybind11::str(strValue, false);
-}
-
 class bytes : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(bytes, object, PYBIND11_BYTES_CHECK)
@@ -691,4 +687,37 @@ inline size_t len(handle h) {
     return (size_t) result;
 }
 
+NAMESPACE_BEGIN(detail)
+template <typename D> iterator object_api<D>::begin() const { return {PyObject_GetIter(derived().ptr()), false}; }
+template <typename D> iterator object_api<D>::end() const { return {nullptr, false}; }
+template <typename D> accessor object_api<D>::operator[](handle key) const { return {derived(), key, false}; }
+template <typename D> accessor object_api<D>::operator[](const char *key) const { return {derived(), key, false}; }
+template <typename D> accessor object_api<D>::attr(handle key) const { return {derived(), key, true}; }
+template <typename D> accessor object_api<D>::attr(const char *key) const { return {derived(), key, true}; }
+template <typename D> args_proxy object_api<D>::operator*() const { return {derived().ptr()}; }
+
+template <typename D>
+pybind11::str object_api<D>::str() const {
+    PyObject *str_value = PyObject_Str(derived().ptr());
+#if PY_MAJOR_VERSION < 3
+    PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
+    Py_XDECREF(str_value); str_value = unicode;
+#endif
+    return {str_value, false};
+}
+
+template <typename D>
+pybind11::str object_api<D>::repr() const {
+    PyObject *str_value = PyObject_Repr(derived().ptr());
+#if PY_MAJOR_VERSION < 3
+    PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
+    Py_XDECREF(str_value); str_value = unicode;
+#endif
+    return {str_value, false};
+}
+
+template <typename D>
+handle object_api<D>::get_type() const { return (PyObject *) Py_TYPE(derived().ptr()); }
+
+NAMESPACE_END(detail)
 NAMESPACE_END(pybind11)