Improve handling of NULL and "(not loaded)" placeholders:

 - Rewrite TableContent and CustomQuery to store NSNull and SPNotLoaded objects in the data arrays where appropriate, rather than providing string conversion on data load.  Faster, simpler comparisons and processing code, slightly lower memory usage, and reduces the chance of bugs caused by inadvertantly processing the string values; we can now also distinguish easily between NULL and "NULL" etc, and further paves the ground for image representations of special values.
 - Fix a bug caused by consistent value reloading when editing BLOB/TEXT columns with deferred loading - if editing a row and revisiting an edited cell, the original value was restored; the original value is now only loaded once.
This addresses the rest of Issue #423.

1 files changed, 91 insertions, 0 deletions

diff --git a/Source/SPNotLoaded.m b/Source/SPNotLoaded.m
new file mode 100644
index 00000000..f8afda1b
--- /dev/null
+++ b/Source/SPNotLoaded.m
@@ -0,0 +1,91 @@
+//
+//  $Id$
+//
+//  SPNotLoaded.m
+//  sequel-pro
+//
+//  Created by Rowan Beentje on 07/10/2009.
+//  Copyright 2009 Rowan Beentje. All rights reserved.
+//
+//  This program is free software; you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation; either version 2 of the License, or
+//  (at your option) any later version.
+//
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with this program; if not, write to the Free Software
+//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//
+//  More info at <http://code.google.com/p/sequel-pro/>
+
+#import "SPNotLoaded.h"
+
+static SPNotLoaded *notLoaded = nil;
+
+@implementation SPNotLoaded
+
+// Return the singleton object
++ (SPNotLoaded *) notLoaded
+{
+	@synchronized(self) {
+		if (notLoaded == nil) {
+			[[self alloc] init];
+		}
+	}
+	return notLoaded;
+}
+
++ (id) allocWithZone:(NSZone *)zone
+{
+	@synchronized(self) {
+		if (notLoaded == nil) {
+			return [super allocWithZone:zone];
+		}
+	}
+	return notLoaded;
+}
+
+- (id) init
+{
+	Class notLoadedClass = [self class];
+	@synchronized(notLoadedClass) {
+		if (notLoaded == nil) {
+			if (self = [super init]) {
+				notLoaded = self;
+			}
+		}
+	}
+	return notLoaded;
+}
+
+- (id) copyWithZone:(NSZone *)zone { return self; }
+
+- (id) retain { return self; }
+
+- (unsigned) retainCount { return UINT_MAX; }
+
+- (void) release {}
+
+- (id) autorelease { return self; }
+
+@end
+
+
+/**
+ * This Category is intended to allow easy testing of all objects for SPNotLoaded.
+ */
+@implementation NSObject (SPNotLoadedTest)
+
+- (BOOL) isSPNotLoaded
+{
+	static id SPNotLoadedForComparison;
+	if (!SPNotLoadedForComparison) SPNotLoadedForComparison = [SPNotLoaded notLoaded];
+    return (self == SPNotLoadedForComparison);
+}
+
+@end
\ No newline at end of file