From 51a01cfebf933d270bf7b7fadb0fb3ca3b7a4cd5 Mon Sep 17 00:00:00 2001
From: Michael Shepanski <michael@codesynthesis.com>
Date: Thu, 6 Nov 2014 16:33:35 +1100
Subject: Implement {query,execute}_{one,value}() shortcut functions

Useful in situations where the query is know to return at most one element
(*_one) or exactly one element (*_value).
---
 hello/driver.cxx | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

(limited to 'hello')

diff --git a/hello/driver.cxx b/hello/driver.cxx
index a049c79..3a4de8c 100644
--- a/hello/driver.cxx
+++ b/hello/driver.cxx
@@ -78,14 +78,16 @@ main (int argc, char* argv[])
     {
       transaction t (db->begin ());
 
-      result r (db->query<person> (query::first == "Joe" &&
-                                   query::last == "Dirt"));
-
-      result::iterator i (r.begin ());
+      // Here we know that there can be only one Joe Dirt in our
+      // database so we use the query_one() shortcut instead of
+      // manually iterating over the result returned by query().
+      //
+      auto_ptr<person> joe (
+        db->query_one<person> (query::first == "Joe" &&
+                               query::last == "Dirt"));
 
-      if (i != r.end ())
+      if (joe.get () != 0)
       {
-        auto_ptr<person> joe (i.load ());
         joe->age (joe->age () + 1);
         db->update (*joe);
       }
@@ -99,11 +101,10 @@ main (int argc, char* argv[])
     {
       transaction t (db->begin ());
 
-      odb::result<person_stat> r (db->query<person_stat> ());
-
-      // The result of this query always has exactly one element.
+      // The result of this (aggregate) query always has exactly one element
+      // so use the query_value() shortcut.
       //
-      const person_stat& ps (*r.begin ());
+      person_stat ps (db->query_value<person_stat> ());
 
       cout << endl
            << "count  : " << ps.count << endl
-- 
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