How do I perform event trigger operations with 'DBAccess' iOS ORM

Question

I am using DBAccess framework v1.6.12 with Xcode 7.1.1.

I would like to use an event trigger when INSERT, UPDATE or DELETE the rows like :

1. Existing specific period data's 'longest' parameter turn into 'NO'.
2. Find the row which has the longest 'text'.
3. Change its row's 'longest' parameter to 'YES'.

Code image:

@interface NoteModel : DBObject
@property uint32_t dateYMD; // not unique
@property BOOL longest; // default value is NO
@property NSString *text;
@end

- (void)test {
    NoteModel *obj = [NoteModel new];
    obj.dateYMD = 20151201;
    obj.text = @"hoge";
    [obj commit]; //< HERE I want to fire the event trigger
}

DBObject#entityWillInsert is just return BOOL value without chaging infos.

Answer 1

To intercept events as you want you would use the following methods:

- (BOOL)entityWillInsert;
- (BOOL)entityWillUpdate;
- (BOOL)entityWillDelete;
- (void)entityDidInsert;
- (void)entityDidUpdate;
- (void)entityDidDelete;

From your example, although I might not be exactly clear with what you are asking, I would use the entityWillInsert/Update methods to query for other objects that may be longer and then you can update the longest flag accordingly.

In semi-psuedo code it would look something like this:

- (BOOL)entityWillInsert {

    // see if we have any existing records with a longer text field
    self.longest = [[[NoteModel query] whereWithFormat:@"length(text) > length(%@)", self.text] count] ? NO:YES;

    // now if this is to be the longest then we will need to ensure that the current record is updated too.
    if(self.longest) { 
       for (NoteModel* r in [[[NoteModel query] where:@"longest = 1"] fetch]) {
            r.longest = NO;
           [r commit];
       }
    }

    // you must return yes to ensure the ORM knows to complete the action
    return YES;

}