opaque<> clarifications

example/example14.cpp

@@ -13,6 +13,11 @@
 
 typedef std::vector<std::string> StringList;
 
+class ClassWithSTLVecProperty {
+public:
+    StringList stringList;
+};
+
 void init_ex14(py::module &m) {
     py::class_<py::opaque<StringList>>(m, "StringList")
         .def(py::init<>())
@@ -20,11 +25,24 @@ void init_ex14(py::module &m) {
         .def("pop_back", [](py::opaque<StringList> &l) { l->pop_back(); })
         .def("back", [](py::opaque<StringList> &l) { return l->back(); });
 
+    py::class_<ClassWithSTLVecProperty>(m, "ClassWithSTLVecProperty")
+        .def(py::init<>())
+        /* Need to cast properties to opaque types to avoid pybind11-internal
+           STL conversion code from becoming active */
+        .def_readwrite("stringList", (py::opaque<StringList> ClassWithSTLVecProperty:: *)
+                                     &ClassWithSTLVecProperty::stringList);
+
     m.def("print_opaque_list", [](py::opaque<StringList> &_l) {
         StringList &l = _l;
-        std::cout << "Opaque list: " << std::endl;
-        for (auto entry : l)
-           std::cout << "  " << entry << std::endl; 
+        std::cout << "Opaque list: [";
+        bool first = true;
+        for (auto entry : l) {
+            if (!first)
+                std::cout << ", ";
+            std::cout << entry;
+            first = false;
+        }
+        std::cout << "]" << std::endl;
     });
 
     m.def("return_void_ptr", []() { return (void *) 1234; });

example/example14.py

@@ -4,10 +4,13 @@ import sys
 sys.path.append('.')
 
 from example import StringList, print_opaque_list
+from example import ClassWithSTLVecProperty
 from example import return_void_ptr, print_void_ptr
 from example import return_null_str, print_null_str
 from example import return_unique_ptr
 
+#####
+
 l = StringList()
 l.push_back("Element 1")
 l.push_back("Element 2")
@@ -16,9 +19,21 @@ print("Back element is %s" % l.back())
 l.pop_back()
 print_opaque_list(l)
 
+#####
+cvp = ClassWithSTLVecProperty()
+print_opaque_list(cvp.stringList)
+
+cvp.stringList = l
+cvp.stringList.push_back("Element 3")
+print_opaque_list(cvp.stringList)
+
+#####
+
 print_void_ptr(return_void_ptr())
 
 print(return_null_str())
 print_null_str(return_null_str())
 
+#####
+
 print(return_unique_ptr())

example/example14.ref

@@ -1,9 +1,8 @@
-Opaque list: 
-  Element 1
-  Element 2
+Opaque list: [Element 1, Element 2]
 Back element is Element 2
-Opaque list: 
-  Element 1
+Opaque list: [Element 1]
+Opaque list: []
+Opaque list: [Element 1, Element 3]
 Got void ptr : 1234
 None
 Got null str : 0