Si bien la respuesta de @BarryWark es correcta cuando se trabaja con solicitudes de búsqueda, quiero escribir una advertencia a las personas que intentarán aplicar esta regla a un filtro de datos básicos para muchas relaciones.
Poco: Si la hora de filtrar a-muchas relaciones que utiliza un predicado y su matriz de objetos para IN consulta es un conjunto de ObjectID - entonces debe usar self.objectID en la cadena de consulta como
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(self.objectID IN %@)", arrayOfObjectIDs];
Dado que usar solo (self IN %@)
en el caso de filtrar a muchas relaciones dará como resultado resultados incorrectos, es solo un NSArray que evalúa predicados y no sabe nada acerca de las cosas NSManagedObjectID de Core Data.
He creado un código de prueba especial que muestra esto. Perdón por tantas líneas, pero valen la pena. Hay dos entidades: usuario y publicación, y el usuario tiene una relación de muchos llamada "publicaciones".
User *user = [NSEntityDescription insertNewObjectForEntityForName:NSStringFromClass([User class]) inManagedObjectContext:managedObjectContext()];
Post *post = [NSEntityDescription insertNewObjectForEntityForName:NSStringFromClass([Post class]) inManagedObjectContext:managedObjectContext()];
[user addPostsObject:post];
[managedObjectContext() save:nil];
// 1. Both filtered relationship array and fetch result are correct!
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(self IN %@)", @[ post ]];
NSSet *filteredRelationship = [user.posts filteredSetUsingPredicate:predicate];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Post"];
NSArray *fetchResult = [managedObjectContext() executeFetchRequest:fetchRequest error:nil];
NSLog(@"\n\n\nPredicate: %@", predicate);
NSLog(@"filteredRelationship: %@", filteredRelationship);
NSLog(@"fetchResult: %@", fetchResult);
// 2. Filtered relationship array is empty (wrong), fetch result is correct, !
predicate = [NSPredicate predicateWithFormat:@"(self IN %@)", @[ post.objectID ]];
filteredRelationship = [user.posts filteredSetUsingPredicate:predicate];
fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Post"];
fetchResult = [managedObjectContext() executeFetchRequest:fetchRequest error:nil];
NSLog(@"\n\n\nPredicate: %@", predicate);
NSLog(@"filteredRelationship: %@", filteredRelationship);
NSLog(@"fetchResult: %@", fetchResult);
// 3. Filtered relationship array is empty (wrong), fetch result is correct
predicate = [NSPredicate predicateWithFormat:@"(self.objectID IN %@)", @[ post ]];
filteredRelationship = [user.posts filteredSetUsingPredicate:predicate];
fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Post"];
fetchResult = [managedObjectContext() executeFetchRequest:fetchRequest error:nil];
NSLog(@"\n\n\nPredicate: %@", predicate);
NSLog(@"filteredRelationship: %@", filteredRelationship);
NSLog(@"fetchResult: %@", fetchResult);
// 4. Filtered relationship array is correct, fetch result is correct
predicate = [NSPredicate predicateWithFormat:@"(self.objectID IN %@)", @[ post.objectID ]];
filteredRelationship = [user.posts filteredSetUsingPredicate:predicate];
fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Post"];
fetchResult = [managedObjectContext() executeFetchRequest:fetchRequest error:nil];
NSLog(@"\n\n\nPredicate: %@", predicate);
NSLog(@"filteredRelationship: %@", filteredRelationship);
NSLog(@"fetchResult: %@", fetchResult);
salida TLDR
<redacted> Predicate: SELF IN {<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: { content = nil; title = nil; user = "0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>"; })}
<redacted> filteredRelationship: {(<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: { content = nil; title = nil; user = "0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>"; }))}
<redacted> fetchResult: ("<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: {\n content = nil;\n title = nil;\n user = \"0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>\";\n})")
<redacted> Predicate: SELF IN {0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1>}
<redacted> filteredRelationship: {()}
<redacted> fetchResult: ("<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: {\n content = nil;\n title = nil;\n user = \"0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>\";\n})")
<redacted> Predicate: objectID IN {<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: { content = nil; title = nil; user = "0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>";})}
<redacted> filteredRelationship: {()}
<redacted> fetchResult: ("<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: {\n content = nil;\n title = nil;\n user = \"0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>\";\n})")
<redacted> Predicate: objectID IN {0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1>}
<redacted> filteredRelationship: {(<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: { content = nil; title = nil; user = "0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>";}))}
<redacted> fetchResult: ("<Post: 0x2a04f10> (entity: Post; id: 0x2a56c40 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/Post/p1> ; data: {\n content = nil;\n title = nil;\n user = \"0x2af2a20 <x-coredata://9D07BF41-2DC0-42C1-9DD8-6082A00E7BEB/User/p1>\";\n})")
Tha Necesita su ayuda. Intenté usar [NSPredicate predicateWithFormat: @ "self NOT IN% @", myArrayOfManagedObjects], pero seguí recibiendo el error "No se pudo analizar el error de cadena de formato" self NOT IN% @ "en el tiempo de ejecución. ¿Algunas ideas? –
Lo siento .. mi error por no probar antes de publicar. He corregido mi respuesta (use "NOT (self IN% @)" en lugar de "self NOT IN% @"). –
Esto funcionó bien para mí. Lo usé para filtrar usando lógica compleja que no es compatible con SQL. Pero predicateWithBlock no funciona (por razones razonables) en SQL. –