对不对,如果标题不好。我试图理解的是:在我在网上找到的核心数据示例中,他们解释了如何使用nsfetchresultcontroller来使用核心数据。但据我所知,nsfetchresultcontroller是为表视图。但我只有2个常规视图控制器。
它非常基本,我有一个用于创建任务的创建页面的视图控制器,另一个是带有标签的主页,用于显示已创建的单个任务:
HomePageViewController.m:
#import "HomePageViewController.h"
#import "CreatTargetViewController.h"
@interface HomePageViewController ()
@property (weak, nonatomic) IBOutlet UILabel *currentTarget;
@end
@implementation HomePageViewController
- (IBAction)unwindToHomePage:(UIStoryboardSegue *)segue
{
CreatTargetViewController *source = (CreatTargetViewController *)[segue sourceViewController];
self.currentTarget.text = source.target.content;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
CreatTargetViewController.h:
#import <UIKit/UIKit.h>
#import "Targets.h"
@interface CreatTargetViewController : UIViewController
@property (nonatomic, strong) Targets *target;
@end
CreatTargetViewController.m:
#import "CreatTargetViewController.h"
#import "Targets.h"
#import "CoreDataStack.h"
@interface CreatTargetViewController ()
@property (weak, nonatomic) IBOutlet UIBarButtonItem *saveButton;
@property (weak, nonatomic) IBOutlet UITextView *myTextView;
@end
@implementation CreatTargetViewController
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if (sender != self.saveButton) return;
if (self.target != nil) {
self.myTextView.text = self.target.content;
}
}
- (void)insertNewTargetEntry
{
CoreDataStack *coreDataStack = [CoreDataStack defaultStack];
Targets *entry = [NSEntityDescription insertNewObjectForEntityForName:@"Targets" inManagedObjectContext:coreDataStack.managedObjectContext];
entry.content = self.myTextView.text;
[coreDataStack saveContext];
}
- (void)updateTargetEntry
{
self.target.content = self.myTextView.text;
CoreDataStack *stack = [CoreDataStack defaultStack];
[stack saveContext];
}
- (IBAction)saveWasPressed:(id)sender
{
if (self.target != nil) {
[self updateTargetEntry];
} else {
[self insertNewTargetEntry];
}
}
- (void)viewWillAppear:(BOOL)animated
{
[self.myTextView becomeFirstResponder];
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
和核心数据堆栈的另一个类:
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
@interface CoreDataStack : NSObject
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
+ (instancetype)defaultStack;
- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;
@end
CoreDataStack.m:
#import "CoreDataStack.h"
@implementation CoreDataStack
#pragma mark - Core Data stack
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
+ (instancetype)defaultStack
{
static CoreDataStack *defaultStack;
static dispatch_once_t onceToken;
dispatch_once (&onceToken, ^{
defaultStack = [[self alloc] init];
});
return defaultStack;
}
- (NSURL *)applicationDocumentsDirectory {
// The directory the application uses to store the Core Data store file. This code uses a directory named "digitalCrown.LaserApp" in the application's documents directory.
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"LaserApp" withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
// Create the coordinator and store
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"LaserApp.sqlite"];
NSError *error = nil;
NSString *failureReason = @"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";
dict[NSLocalizedFailureReasonErrorKey] = failureReason;
dict[NSUnderlyingErrorKey] = error;
error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _persistentStoreCoordinator;
}
- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}
#pragma mark - Core Data Saving support
- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
NSError *error = nil;
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
如何在此处传达数据?