Simple Introduction to Core Data

1. Adding entities in. xcdatamodeld

2. Add the corresponding entity class

3. Import (Coredata.framework has selected use core Data auto-add at the beginning)

4. Initialization of response information

To load a model file from an application package
Nsmanagedobjectmodel *model = [Nsmanagedobjectmodel Mergedmodelfrombundles:nil];

Initializing persisted objects
Nspersistentstorecoordinator *per=[[nspersistentstorecoordinator Alloc]initwithmanagedobjectmodel:model];

Create Sqlight Path
NSString *path=[nssearchpathfordirectoriesindomains (NSDocumentDirectory, Nsuserdomainmask, YES) firstObject];
Nsurl *url=[nsurl fileurlwithpath:[path stringbyappendingpathcomponent:@ "Person.data"];

Adding persistent storage
Nserror *error=nil;
Nspersistentstore *store = [per addpersistentstorewithtype:nssqlitestoretype configuration:nil URL:url Options:nil error:&error];

if (store = = nil) {//Direct throw exception
[NSException raise:@ "Add Database Error" format:@ "%@", [Error localizeddescription]];

NSLog (@ "failed to open the database! ---%@ ", error.localizeddescription);

}else{

NSLog (@ "Open database successfully! ");

Initialize context, set Persistentstorecoordinator property
Self.context = [[Nsmanagedobjectcontext alloc] init];
_context.persistentstorecoordinator = per;
}

Now it is possible to make a deletion check based on context contexts.

5. Add Data

Incoming context, initializing a person
Nsmanagedobject *person=[nsentitydescription insertnewobjectforentityforname:@ "Person" InManagedObjectContext: Self.context];
[Person setvalue:@ "Zhang San" forkeypath:@ "name"];
[Person Setvalue:[nsnumber numberwithint:25] forkeypath:@ ' age ';
//
Initialize Card
Nsmanagedobject *card=[nsentitydescription insertnewobjectforentityforname:@ "card" Inmanagedobjectcontext: Self.context];
[Card setvalue:@ "1234567" forkeypath:@ "no"];
//
Create a card and person relationship
[Person Setvalue:card forkeypath:@ "card"];

2) Model mode
Person *person=[nsentitydescription insertnewobjectforentityforname:@ ' person ' inManagedObjectContext:self.context ];
person.name=@ "Zhang San";
Person.age=[nsnumber numberwithint:25];

Card *card=[nsentitydescription insertnewobjectforentityforname:@ "card" inManagedObjectContext:self.context];
card.no=@ "123456";

Person.card=card;

Saving data with context
Nserror *error=nil;

BOOL Result=[self.context save:&error];

if (result) {
NSLog (@ "Insert success");
}else{
NSLog (@ "Insert failed");
}

6. Querying data

Nsfetchrequest *fetchrequest = [[Nsfetchrequest alloc] init];
Nsentitydescription *entity = [nsentitydescription entityforname:@ "person" inManagedObjectContext:self.context];
[Fetchrequest setentity:entity];

When setting conditional filtering,% in a database SQL statement is replaced by *
Nspredicate *predicate = [nspredicate predicatewithformat:@ "name like%@", @ "Zhang"];
[Fetchrequest Setpredicate:predicate];

Sort
Nssortdescriptor *sortdescriptor = [[Nssortdescriptor alloc] initwithkey:@ "age"
Ascending:yes];
[Fetchrequest Setsortdescriptors:[nsarray Arraywithobjects:sortdescriptor, Nil]];

Nserror *error = nil;
Nsarray *fetchedobjects = [Self.context executefetchrequest:fetchrequest error:&error];
if (fetchedobjects = = nil) {
NSLog (@ "Query failed");
}else
{
For (person *obj in fetchedobjects) {
Card *car= (Card *) (Obj.card);
NSLog (@ "name:%@", car.no);
}
}

7. Delete Data

Nsfetchrequest *fetchrequest = [[Nsfetchrequest alloc] init];
Nsentitydescription *entity = [nsentitydescription entityforname:@ "person" inManagedObjectContext:self.context];
[Fetchrequest setentity:entity];


Nspredicate *predicate = [nspredicate predicatewithformat:@ "age=%@", [NSNumber numberwithint:25]];
[Fetchrequest Setpredicate:predicate];

Nserror *error = nil;
Nsarray *fetchedobjects = [Self.context executefetchrequest:fetchrequest error:&error];
if (fetchedobjects! = nil) {
For (person *obj in fetchedobjects) {
[Self.context Deleteobject:obj];
}

Nserror *error=nil;
[Self.context save:&error];
if (Error) {
NSLog (@ "Delete error");
}else {
NSLog (@ "Delete succeeded");
}
}

Simple Introduction to Core Data