From f443b90f0d3f47a3ca78fcf4ef5f8b95dd33a72e Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 14 Jan 2011 11:13:18 +0200
Subject: Document default ctor requirements, odb::access usage

---
 doc/manual.xhtml | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/doc/manual.xhtml b/doc/manual.xhtml
index bdfb6fd..64d873a 100644
--- a/doc/manual.xhtml
+++ b/doc/manual.xhtml
@@ -1622,7 +1622,6 @@ class person
 {
   ...
 
-private:
   #pragma db id
   unsigned long id_;
 };
@@ -1633,6 +1632,41 @@ private:
      the database-related properties of a class and its
      members (see <a href="#5">Chapter 5, "ODB Pragma Language"</a>).</p>
 
+  <p>Normally, an object class should define the default constructor. The
+     generated database support code uses this constructor when
+     instantiating an object from the persistent state. If you add the
+     default constructor only for the database support code, then you
+     can make it private. It is also possible to have an object type
+     without the default constructor. However, in this case, the database
+     operations can only load the persistent state into an existing instance
+     (<a href="#3.5">Section 3.5, "Loading Persistent Objects"</a>,
+     <a href="#4.4">Section 4.4, "Query Result"</a>).</p>
+
+  <p>If an object class has private or protected non-transient data
+     members or if its default constructor is not public, then the
+     <code>odb::access</code> class, defined in the
+     <code>&lt;odb/core.hxx></code> header, should be declared a
+     friend of this object type. For example:</p>
+
+  <pre class="c++">
+#include &lt;odb/core.hxx>
+
+#pragma db object
+class person
+{
+  ...
+
+private:
+  friend class odb::access;
+
+  person () {}
+
+  #pragma db id
+  unsigned long id_;
+};
+  </pre>
+
+
   <p>You may be wondering whether we also have to declare value types
      as persistent. We don't need to do anything special for simple value
      types such as <code>int</code> or <code>std::string</code> since the
@@ -1652,7 +1686,6 @@ class name
 {
   ...
 
-private:
   std::string first_;
   std::string last_;
 };
-- 
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