在两个常规视图控制器之间获取核心数据中数据的最佳方法是什么?

时间:2014-11-03 19:27:50

标签: ios objective-c core-data

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?

0 个答案:

没有答案