This commit was manufactured by cvs2svn to create tag

'Version_1_21_0'.

[SVN r9525]

example/getting_started3.cpp

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+/*
+    This example shows how to make an Extension Class "pickleable".
+
+    Python's pickle module implements a basic but powerful algorithm
+    for "pickling" (a.k.a. serializing, marshalling or flattening)
+    nearly arbitrary Python objects.
+
+    The user can influence how an Extension Class instance is pickled
+    by defining three special methods: __getinitargs__(),
+    __getstate__(), and __setstate(). This interface is similar to
+    that for regular Python classes as described in detail in the
+    Python Library Reference for pickle:
+
+    http://www.python.org/doc/current/lib/module-pickle.html
+
+    When an Extension Class instance is pickled, __getinitargs__() is
+    called, if implemented. This method should return a tuple
+    containing the arguments to be passed to the class constructor when
+    the object is restored.
+
+    If there is no __getstate__() method, the instance's __dict__ is
+    pickled if it is not empty. If __getstate__() is defined, it should
+    return an object representing the state of the instance.
+
+    If there is no __setstate__() method, __getstate__() must return a
+    dictionary. When the instance is restored, the items in this dictionary
+    are added to the instance's __dict__.
+
+    If the Extension Class defines __setstate__(), the pickle loader
+    calls it with the result of __getstate__() as arguments. In this
+    case, the state object need not be a dictionary.  The
+    __getstate__() and __setstate__() methods can do what they want.
+
+    If both __getinitargs__() and __getstate__() are defined, the
+    instance is restored by first calling the constructor with
+    the result of __getinitargs__() as argument. After the instance
+    is reconstructed, the __dict__ is updated or __setstate__() is
+    called if implemented.
+
+    The mechanism described here is an exact replication of that one
+    implemented by Jim Fulton's ExtensionClass (included in Zope 2.2.2).
+ */
+
+#include <iostream>
+#include <string>
+
+#include <boost/python/class_builder.hpp>
+namespace python = boost::python;
+
+namespace { // Avoid cluttering the global namespace.
+
+  // A friendly class.
+  class world
+  {
+    private:
+      std::string country;
+      int secret_number;
+    public:
+      world(const std::string& country) : secret_number(0) {
+        this->country = country;
+      }
+      std::string greet() const { return "Hello from " + country + "!"; }
+      std::string get_country() const { return country; }
+      void set_secret_number(int number) { secret_number = number; }
+      int get_secret_number() const { return secret_number; }
+  };
+
+  // Support for pickle.
+  python::tuple world_getinitargs(const world& w) {
+      python::tuple result(1);
+      result.set_item(0, w.get_country());
+      return result;
+  }
+
+  python::tuple world_getstate(const world& w) {
+      python::tuple result(1);
+      result.set_item(0, w.get_secret_number());
+      return result;
+  }
+
+  void world_setstate(world& w, python::tuple state) {
+    if (state.size() != 1) {
+      PyErr_SetString(PyExc_ValueError,
+        "Unexpected argument in call to __setstate__.");
+      throw python::error_already_set();
+    }
+    int number = BOOST_PYTHON_CONVERSION::from_python(state[0].get(),
+      python::type<int>());
+    if (number != 42)
+      w.set_secret_number(number);
+  }
+}
+
+BOOST_PYTHON_MODULE_INIT(getting_started3)
+{
+  try
+  {
+    // Create an object representing this extension module.
+    python::module_builder this_module("getting_started3");
+
+    // Create the Python type object for our extension class.
+    python::class_builder<world> world_class(this_module, "world");
+
+    // Add the __init__ function.
+    world_class.def(python::constructor<std::string>());
+    // Add a regular member function.
+    world_class.def(&world::greet, "greet");
+    world_class.def(&world::get_secret_number, "get_secret_number");
+    world_class.def(&world::set_secret_number, "set_secret_number");
+
+    // Support for pickle.
+    world_class.def(world_getinitargs, "__getinitargs__");
+    world_class.def(world_getstate, "__getstate__");
+    world_class.def(world_setstate, "__setstate__");
+  }
+  catch(...)
+  {
+    python::handle_exception(); // Deal with the exception for Python
+  }
+}