Re: GDL2: fetching all objects from a database to a custom class

[Manuel Guesdon]

Hi,

On Fri, 22 Aug 2003 10:31:34 +0200 Frédéric PRACA 
<frederic.praca@freebsd-fr.org> wrote:

>| Hi everybody,
>| today I tried to make a sample (and simple) application using GDL2.
>| The goal of this application is to connect to a database and retrieve data 
>to 
>| put it in custom classes. The question will be simple : how do I do that ? I 
>| searched in headers files but even if I can find method names, it's 
>impossible 
>| to find the sequence to use.
>| Here's what I've done :
>| - construct a model from a file
>| - create a EODatabase from that model
>| - create an EOQualifier with format
>| - create an EOFetchSpecification with entity
>| - retrieve an EOEditingContext from EODatabase
>| - applied the context the objectsWithFetchSpecifiation and the NSArray is 
>| empty ;-(
>| In fact, I just wanted to retrieve all the objects of my custom class from 
>the 
>| database. Is there a straight way to do that ? Where can I find code 
>examples 
>| and an howto-like ?
>| 

Here is a exemple to fetch a record, change one of it's property and save it:

// Create Model Group
EOModelGroup *group = [EOModelGroup new];

// The path to eomodeld directory
NSString* modelPath=@"/Path/To/My.eomodeld";

// Adapt Postgres date format
[NSCalendarDate setPostgres95Format:@"%m/%d/%Y %H:%M:%S%z"];

// add a model based on our eomodeld directory
dbModel=[group addModelWithFile:modelPath];

// Be paranoiac.
NSAssert(dbModel,@"No dbModel");

[EOModelGroup setDefaultGroup:group];

[group release];

// Create database
EODatabase* database = [[[EODatabase alloc] initWithModel:_dbModel] 
autorelease];

// Create database context with database
EODatabaseContext* dbContext  = [[[EODatabaseContext alloc] 
initWithDatabase:database] autorelease];

// Yes, we want debugging information
[[dbContext adaptorContext] setDebugEnabled:YES];

// add objectStore
[[EOObjectStoreCoordinator defaultCoordinator] 
addCooperatingObjectStore:dbContext];

// Create Editing Context
EOEditingContext* myEditingContext=[EOEditingContext new];

// Get the record which have 1 as code from entity 'Test'
EOGenericRecord* aRec=[myEditingContext objectMatchingValue:@"1"
                                        forKey:@"code"
                                        entityNamed:@"Test"];

// Dump the record
NSLog(@"aRec=%@",aRec);
NSLog(@"Property XX of the record=%@",[aRec valueForKey:@"XX"];

// Now change XX property
[aRec takeValue:@"blabla"
      forKey:@"XX"];

// Verify the change :-)
NSMLog(@"aRec=%@",aRec);

// Save change
[myEditingContext saveChanges];




Instead of fetching one record matching a value, you can use other methods 
defined in EOUtilities.h


Have fun !

Manuel

-- 
______________________________________________________________________
Manuel Guesdon - ORANGE CONCEPT <mguesdon@orange-concept.com>
14 rue Jean-Baptiste Clement  -  93200 Saint-Denis  -  France
Tel: +33 1 4940 0997  -  Fax: +33 1 4940 0998