[gnome-boxes] Make MediaManager a singleton

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit ca2c92684c3f05aa43e7091b0e8652dfe90dd0f7
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Fri Oct 5 05:06:55 2012 +0300

    Make MediaManager a singleton
    
    https://bugzilla.gnome.org/show_bug.cgi?id=688770

 src/media-manager.vala |   26 +++++++++++++++++---------
 src/wizard.vala        |    2 +-
 2 files changed, 18 insertions(+), 10 deletions(-)
---
diff --git a/src/media-manager.vala b/src/media-manager.vala
index 601ed4c..ea46a61 100644
--- a/src/media-manager.vala
+++ b/src/media-manager.vala
@@ -5,6 +5,7 @@ using GUdev;
 using Tracker;
 
 private class Boxes.MediaManager : Object {
+    private static MediaManager media_manager;
     private const string SPARQL_QUERY = "SELECT nie:url(?iso) nie:title(?iso) osinfo:id(?iso) osinfo:mediaId(?iso)" +
                                         " { ?iso nfo:isBootable true }";
 
@@ -13,15 +14,11 @@ private class Boxes.MediaManager : Object {
 
     private Sparql.Connection connection;
 
-    public MediaManager () {
-        client = new GUdev.Client ({"block"});
-        os_db = new OSDatabase ();
-        os_db.load.begin ();
-        try {
-            connection = Sparql.Connection.get ();
-        } catch (GLib.Error error) {
-            critical ("Error connecting to Tracker: %s", error.message);
-        }
+    public static MediaManager get_instance () {
+        if (media_manager == null)
+            media_manager = new MediaManager ();
+
+        return media_manager;
     }
 
     public async InstallerMedia create_installer_media_for_path (string       path,
@@ -83,6 +80,17 @@ private class Boxes.MediaManager : Object {
         return list;
     }
 
+    private MediaManager () {
+        client = new GUdev.Client ({"block"});
+        os_db = new OSDatabase ();
+        os_db.load.begin ();
+        try {
+            connection = Sparql.Connection.get ();
+        } catch (GLib.Error error) {
+            critical ("Error connecting to Tracker: %s", error.message);
+        }
+    }
+
     private static int compare_media (InstallerMedia media_a, InstallerMedia media_b) {
         return strcmp (media_a.label, media_b.label);
     }
diff --git a/src/wizard.vala b/src/wizard.vala
index c187132..ec22c3e 100644
--- a/src/wizard.vala
+++ b/src/wizard.vala
@@ -129,7 +129,7 @@ private class Boxes.Wizard: Boxes.UI {
     construct {
         steps = new GenericArray<Gtk.Label> ();
         steps.length = WizardPage.LAST;
-        media_manager = new MediaManager ();
+        media_manager = MediaManager.get_instance ();
     }
 
     private void wizard_source_update_next () {