[IOS] Core Data Code Quick Check Table

The code in this article is from: http://www.appcoda.com/introduction-to-core-data/

Students who want to learn Core Data do not miss:) Here are some of the frequently used code snippets for my personal records.

There is a entity:device with three properties: Company, name, version.

1. Get the Context method:

-(Nsmanagedobjectcontext *) managedobjectcontext {    Nsmanagedobjectcontext *context = nil;    ID delegate = [[UIApplication sharedapplication] delegate];    if ([Delegate performselector: @selector (managedobjectcontext)]) {        context = [delegate managedobjectcontext];    }    return context;}

2. Add a piece of data:

    Nsmanagedobjectcontext *context = [self managedobjectcontext];        Create a new Managed object    nsmanagedobject *newdevice = [Nsentitydescription insertnewobjectforentityforname:@ " Device "Inmanagedobjectcontext:context";    [Newdevice setValue:self.nameTextField.text forkey:@ "name"];    [Newdevice setValue:self.versionTextField.text forkey:@ "version"];    [Newdevice setValue:self.companyTextField.text forkey:@ "Company"];        Nserror *error = nil;    Save the object to persistent store    if (![ Context Save:&error]) {        NSLog (@ "Can ' t save!%@%@", error, [error localizeddescription]);    }

3. Delete a single piece of data:

Nsmanagedobjectcontext *context = [self managedobjectcontext];//Delete object from Database[context deleteobject:[ Self.devices ObjectAtIndex:indexPath.row]]; Nserror *error = nil;if (![ Context Save:&error]) {    NSLog (@ "Can ' t delete!%@%@", error, [error localizeddescription]);    return;}

4. Modify a piece of data:

Nsmanagedobjectcontext *context = [self managedobjectcontext];    Update existing Device[self.device setValue:self.nameTextField.text forkey:@ "name"]; [Self.device setValue:self.versionTextField.text forkey:@ "version"]; [Self.device setValue:self.companyTextField.text forkey:@ "Company"]; Nserror *error = nil;//Save The object to persistent Storeif (![ Context Save:&error]) {    NSLog (@ "Can ' t save!%@%@", error, [error localizeddescription]);}

5. Query a bunch of data:

Fetch the devices from persistent data storensmanagedobjectcontext *managedobjectcontext = [self managedobjectcontext] ; Nsfetchrequest *fetchrequest = [[Nsfetchrequest alloc] initwithentityname:@ "Device"];self.devices = [[ Managedobjectcontext executefetchrequest:fetchrequest Error:nil] mutablecopy];

[IOS] Core Data Code Quick Check Table