Thanks for the comment. I haven’t used SLPO for a while, but I really thought you could just use an NSArray as a property to create a 1-to-many relationship. Have you tried that>

Matt

Thanks!

I’m not sure if SQLite really does have foreign keys, check out http://www.sqlite.org/omitted.html . There’s lots of people which mention how to do foreign key constraints (properly) using triggers.

That’s a good idea to ask Jeff, but also, take a look in the source code itself (the file of interest is http://code.google.com/p/sqlitepersistentobjects/source/browse/trunk/src/SQLitePersistentObject.m). You’ll notice that it creates a cross reference table to do the “foreign key” behaviour.

I still don’t quite know why you are having issues with it, it will work exactly as you expect by only having to store things once.

Matt

By the way, i have dropped email to Jeff (author of the SQLitePersistentObject), but looks like he went to the WWDC, I’ll update you with info when I receive reply.

Yes, that’s right. SQLite doesn’t have foreign keys. It will store it as a text field and in that field it will store something which SQLitePersistentObject knows how to find the relevant object in the other table. Does that make sense?

Does it work for you? i.e. can you save and load objects correctly?

Matt

In my real app, I have four classes (Application, Country, Currency, Downloads)

Downloads, contains references to Application, Country and Currency, here is example:

@interface Downloads : SQLitePersistentObject {
Application *application;
Country *country;
Currency *currency;
float royalty;
int units;
int isUpdate;
NSDate *date;
NSString *appId;
}
@property (nonatomic, retain) Application *application;
@property (nonatomic, retain) Country *country;
@property (nonatomic, retain) Currency *currency;
@property (assign) float royalty;
@property (assign) int units;
@property (assign) int isUpdate;
@property (nonatomic, retain) NSDate *date;
@property (nonatomic, retain) NSString *appId;
@end

Example of Application class:

@interface Application : SQLitePersistentObject {
NSString *name;
}
@property (nonatomic, retain) NSString *name;
@end

And here is DB Schema created by SQLitePersistent

CREATE TABLE downloads (pk INTEGER PRIMARY KEY, application TEXT, app_id TEXT, is_update INTEGER, royalty REAL, currency TEXT, country TEXT, date REAL, units INTEGER)

application, currency and country are TEXT field, no foreign keys created. What I’ve done wrong?

Thanks in advance.

One thing to note, in order for SQLLitePersistentObject to save a link to another object, that other object must also be a subclass of SQLLitePersistentObject, or at least some type of object which it knows how to save (Number, Data, String, etc).

Can you check that Car is a subclass of SQLLitePersistentObject as well please?

Thanks,
Matt

I tried to use something like this

@interface Person : SQLitePersistentObject {
Car *car;
// …. your code ….
}
@property (nonatomic, retain) Car *car;
// …. your code ….
@end

However SQLitePersistent doesn’t create any references, just TEXT fields, and store there [car description] as I suppose.

Any ideas how to create real foreign key to another model?

Thanks in advance.