From 0ac8f52ddfae8537651c65b8ab8b32db47756e74 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 4 Feb 2015 17:23:54 +0200
Subject: Implement object loading views

See section 10.2 in the manual for details.
---
 view/README       |  5 +++--
 view/driver.cxx   | 38 ++++++++++++++++++++++++++++++++++++++
 view/employee.hxx | 15 +++++++++++++++
 view/makefile     |  2 +-
 4 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/view/README b/view/README
index 0ade8ea..cba23b9 100644
--- a/view/README
+++ b/view/README
@@ -28,13 +28,14 @@ employee.sql
   following command line:
 
   odb -d <database> --generate-schema --generate-query \
-  --default-pointer std::tr1::shared_ptr employee.hxx
+  --default-pointer std::tr1::shared_ptr --generate-session employee.hxx
 
   Where <database> stands for the database system we are using, for example,
   'mysql'.
 
   The --default-pointer option is used to make TR1 shared_ptr the default
-  object pointer.
+  object pointer. The --generate-session option is used to enable session
+  support for all the objects which is required to use object loading views.
 
 database.hxx
   Contains the create_database() function which instantiates the concrete
diff --git a/view/driver.cxx b/view/driver.cxx
index cbe26ee..74d6eed 100644
--- a/view/driver.cxx
+++ b/view/driver.cxx
@@ -277,6 +277,44 @@ main (int argc, char* argv[])
       t.commit ();
     }
 
+    // The same but using the object loading view.
+    //
+    {
+      typedef odb::query<employee_country_objects> query;
+      typedef odb::result<employee_country_objects> result;
+
+      transaction t (db->begin ());
+
+      // We have to use a session in order for the object pointers
+      // in our view and object pointers inside objects that we load
+      // to point to the same instances, where appropriate.
+      //
+      session s;
+
+      result r (db->query<employee_country_objects> (
+                  query::res::name == query::nat::name));
+
+      cout << "Employees residing inside the country of nationality" << endl;
+
+      for (result::iterator i (r.begin ()); i != r.end (); ++i)
+      {
+        assert (i->e->nationality () == i->nat);
+        assert (i->e->residence () == i->res);
+
+        const employee& e (*i->e);
+        const country& r (*i->res);
+        const country& n (*i->nat);
+
+        cout << "  " << e.first () << " " << e.last () << " "
+             << r.name () << " " << n.name () << endl;
+      }
+
+      cout << endl;
+
+      t.commit ();
+    }
+
+
     // Get the list of employees that have accumulated vacation days.
     //
     {
diff --git a/view/employee.hxx b/view/employee.hxx
index 39d494f..87f0bce 100644
--- a/view/employee.hxx
+++ b/view/employee.hxx
@@ -239,6 +239,21 @@ struct employee_country
   std::string nat_country_name;
 };
 
+// An example of an object loading view. It is a different version of
+// the above view that loads the complete objects instead of a subset
+// of their data members.
+//
+#pragma db view object(employee) \
+  object(country = res: employee::residence_) \
+  object(country = nat: employee::nationality_)
+struct employee_country_objects
+{
+  shared_ptr<employee> e;
+  shared_ptr<country> res;
+  shared_ptr<country> nat;
+};
+
+
 // An example of a native view that provides a complete query and is based
 // on an ad-hoc table. This view allows us to load the employee vacation
 // information from the legacy employee_extra table.
diff --git a/view/makefile b/view/makefile
index cfb061a..ca85d9b 100644
--- a/view/makefile
+++ b/view/makefile
@@ -46,7 +46,7 @@ gen  := $(addprefix $(out_base)/,$(genf))
 $(gen): $(odb)
 $(gen): odb := $(odb)
 $(gen) $(dist): export odb_options += --generate-query --generate-schema \
---default-pointer std::tr1::shared_ptr --table-prefix view_
+--default-pointer std::tr1::shared_ptr --generate-session --table-prefix view_
 $(gen): cpp_options := -I$(src_base)
 $(gen): $(odb.l.cpp-options)
 
-- 
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