I use Jeff LaMarche’s and his contributor’s SQLite Persistent Objects library in my upcoming iPhone application. This library was created before version 3 of the iPhone OS was released. Because iPhone OS v3 contained Core Data, Jeff and his contributors ceased further development. Yet, I was dependent on it and, hence, I continued private development.
My changes were primarily performance enhancements and some reorganization of the main header files to support better life cycle management of the databases. In particular, I added a static variable to hold a static NSDateFormatter. (An NSDateFormatter is surprisingly expensive to create on each SQLite transaction involving a time stamp.) I also defined a new mechanisms to hold the propertiesWithEncodedTypes as a class static. These properties are static with respect to each class. Hence, caching the dictionary, which is used on almost every call to the class, is an excellent performance enhancement.
To use this new feature to optimize your classes, you need to override +propertiesWithEncodedTypes. Here is the code your need to place in your class:
+ (NSDictionary *) propertiesWithEncodedTypes {
static NSDictionary *classProperties = nil;
if (classProperties == nil) {
// Because it is stored in a static, we must retain it.
classProperties = [[self propertiesWithEncodedTypes_] retain];
}
return classProperties;
} // propertiesWithEncodedTypes
Due to these enhancements this library is not thread safe. Because there are other static variables sprinkled throughout the code, which also preclude thread safety, this is not a change in the library’s lack of thread safety.
The license agreement used by this project was legally dubious. With Mr. LaMarche’s formal agreement via email, as the voice of the project, I have edited each project file to be covered by the OSI approved New BSD license. This license, while supporting the values expressed by Jeff during the creation of the project, adds liability protection to each contributor and formally defines the criteria to use the code. Let me be clear, each contributor was facing an unspecified legal liability under the old license. They are now protected. I contribute my changes to this code under the below license.
I hope you find my changes useful and the license agreement a legal improvement. Here is a link to a zip of the archive, 091023 SQLite Persistent Objects.zip. And a link to Jeff’s extremely useful presentation at the 360 iDev Conference.
Enjoy and Anon,
Andrew
SQLite Persistent Objects for Cocoa and Cocoa Touch.
Copyright (c) 2008 – 2009,
Jeff LaMarche,
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