无法将NSManagedObjectContext传递到我的视图控制器 [英] Unable to pass NSManagedObjectContext to my view controller
问题描述
好吧，我可能在我的头上，但怀疑我缺少一些相当根本的东西。我已经搜索堆栈和其他论坛寻求解决方案的帮助。我试过所有的解决方案，我发现，但没有工作，我的情况，我看不到我失踪了。
我创建了一个CoreData应用程序。所有在使用我的appDelegate中的NSManagedObjectContext读取和写入数据到CoreData存储。我已经检查，看看NSManagedObjectContext是否设置在我的AppDelegate，它是。在传递给我唯一的viewController后，我检查它是否设置，它不是。这显然是我的问题。我试过一切，不能解决的解决方案，现在累了，想睡觉。我是iOS的新手，所以我确定它是一些基本的东西。
这是我的代码。
AppDelegate.m
#importAppDelegate.h
#importViewController.h
#importRecipe.h
@interface AppDelegate（）
@property（nonatomic，strong）NSManagedObjectContext * managedObjectContext;
@property（nonatomic，strong）NSManagedObjectModel * managedObjectModel;
@property（nonatomic，strong）NSPersistentStoreCoordinator * persistentStoreCoordinator;
@property（nonatomic，strong）ViewController * viewController;
@end
@implementation AppDelegate
@synthesize managedObjectModel，managedObjectContext，persistentStoreCoordinator，viewController;
@synthesize window = _window;
- （BOOL）application：（UIApplication *）application didFinishLaunchingWithOptions：（NSDictionary *）launchOptions
{
NSManagedObjectContext * context = [self managedObjectContext];
if（！context）{
NSLog（@有一个错误！
}
if（context == nil）{
NSLog（@Context is nil in appdelegate）;
}
else {
NSLog（@Context is set in appdelegate）;
}
viewController.managedObjectContext = self.managedObjectContext;
//应用程序启动后覆盖自定义点。
return YES;
}
#pragma mark - 核心数据
- （NSManagedObjectModel *）managedObjectModel
{
if（managedObjectModel == nil）{
NSString * modelPath = [[NSBundle mainBundle] pathForResource：@RecipeBookofType：@momd];
NSURL * modelURL = [NSURL fileURLWithPath：modelPath];
managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL：modelURL];
}
return managedObjectModel;
}
- （NSString *）documentsDirectory
{
NSArray * paths = NSSearchPathForDirectoriesInDomains（NSDocumentDirectory，NSUserDomainMask，YES）;
NSString * documentsDirectory = [paths objectAtIndex：0];
return documentsDirectory;
}
- （NSString *）dataStorePath
{
return [[self documentsDirectory] stringByAppendingPathComponent：@DataStore.sqlite];
}
- （NSPersistentStoreCoordinator *）persistentStoreCoordinator
{
if（persistentStoreCoordinator == nil）{
NSURL * storeURL = [NSURL fileURLWithPath：[self dataStorePath]];
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel：self.managedObjectModel];
NSError * error;
if（！[persistentStoreCoordinator addPersistentStoreWithType：NSSQLiteStoreType configuration：nil URL：storeURL options：nil error：& error]）{
NSLog（@添加持久存储％@，％@ [error userInfo]）;
abort（）;
}
}
return persistentStoreCoordinator;
}
- （NSManagedObjectContext *）managedObjectContext
{
if（managedObjectContext == nil）{
NSPersistentStoreCoordinator * coordinator = self.persistentStoreCoordinator;
if（coordinator！= nil）{
managedObjectContext = [[NSManagedObjectContext alloc] init];
[managedObjectContext setPersistentStoreCoordinator：coordinator];
}
}
return managedObjectContext;
}
@end
ViewController.h
#import< UIKit / UIKit.h>
@interface ViewController：UITableViewController {
NSArray * recipes;
NSManagedObjectContext * managedObjectContext;
}
@property（nonatomic，retain）NSArray * recipes;
@property（nonatomic，retain）NSManagedObjectContext * managedObjectContext;
@end
ViewController.m
#importViewController.h
#importRecipe.h
@interface ViewController（）
@end
@implementation ViewController
@synthesize recipes;
@synthesize managedObjectContext;
- （void）viewDidLoad
{
[super viewDidLoad];
NSLog（@View Did Load）;
NSManagedObjectContext * context = [self managedObjectContext];
if（！context）{
NSLog（@有一个错误！
}
if（context == nil）{
NSLog（@Context is nil in viewController）;
}
else {
NSLog（@Context is set in viewController）;
}
}
- （BOOL）shouldAutorotateToInterfaceOrientation：（UIInterfaceOrientation）interfaceOrientation
{
if（[[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone）{
return（interfaceOrientation！= UIInterfaceOrientationPortraitUpsideDown）;
} else {
return YES;
}
}
- （void）viewDidUnload {
[super viewDidUnload];
}
@end
我知道NSManagedObjectContext是nil在我的ViewController。问题是我如何将我的上下文从AppDelegate传递到ViewController？我不想从我的viewControllers（更多的希望可以添加）问我的AppDelegate每次我想查询CoreData，我想通过managedObjectContext。
我希望一切都有意义。 ：）
我发现了我的问题的答案。 managedObjectContext没有正确传递给我的viewController。
我使用的是：
code> viewController.managedObjectContext = self.managedObjectContext;
当我应该使用：
ViewController * viewController =（ViewController *）self.window.rootViewController;
viewController.managedObjectContext = self.managedObjectContext;
感谢user523234把我放在正确的行上。
Ok, I may be in well over my head here, but suspect I am missing something quite fundamental. I have searched on stack and other forums for help on finding a solution. I've tried all the solutions I have found but none work for my situation and I cannot see what I am missing.
I have created a CoreData app. All works fine in reading and writing data to the CoreData store using NSManagedObjectContext within my appDelegate. I have checked to see if the NSManagedObjectContext is set in my AppDelegate and it is. After passing it to my only viewController I check to see if it is set and it isn't. So that is clearly my issue. I have tried everything and cannot fathom the solution, now tired and want to go to bed. I'm pretty new to iOS, so I am sure it's something fundamental.
Here's my code as it stands.
AppDelegate.m
#import "AppDelegate.h"
#import "ViewController.h"
#import "Recipe.h"
@interface AppDelegate()
@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, strong) NSPersistentStoreCoordinator *persistentStoreCoordinator;
@property (nonatomic, strong) ViewController *viewController;
@end
@implementation AppDelegate
@synthesize managedObjectModel, managedObjectContext, persistentStoreCoordinator, viewController;
@synthesize window = _window;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
NSManagedObjectContext *context = [self managedObjectContext];
if (!context) {
NSLog(@"There is an error!!!");
}
if (context == nil) {
NSLog(@"Context is nil in appdelegate");
}
else {
NSLog(@"Context is set in appdelegate");
}
viewController.managedObjectContext = self.managedObjectContext;
// Override point for customization after application launch.
return YES;
}
#pragma mark - Core Data
- (NSManagedObjectModel *)managedObjectModel
{
if (managedObjectModel == nil) {
NSString *modelPath = [[NSBundle mainBundle] pathForResource:@"RecipeBook" ofType:@"momd"];
NSURL *modelURL = [NSURL fileURLWithPath:modelPath];
managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
}
return managedObjectModel;
}
- (NSString *)documentsDirectory
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return documentsDirectory;
}
- (NSString *)dataStorePath
{
return [[self documentsDirectory] stringByAppendingPathComponent:@"DataStore.sqlite"];
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (persistentStoreCoordinator == nil) {
NSURL *storeURL = [NSURL fileURLWithPath:[self dataStorePath]];
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];
NSError *error;
if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
NSLog(@"Error adding persistent store %@, %@", error, [error userInfo]);
abort();
}
}
return persistentStoreCoordinator;
}
- (NSManagedObjectContext *)managedObjectContext
{
if (managedObjectContext == nil) {
NSPersistentStoreCoordinator *coordinator = self.persistentStoreCoordinator;
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] init];
[managedObjectContext setPersistentStoreCoordinator:coordinator];
}
}
return managedObjectContext;
}
@end
ViewController.h
#import <UIKit/UIKit.h>
@interface ViewController : UITableViewController {
NSArray *recipes;
NSManagedObjectContext *managedObjectContext;
}
@property (nonatomic, retain) NSArray *recipes;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;
@end
ViewController.m
#import "ViewController.h"
#import "Recipe.h"
@interface ViewController ()
@end
@implementation ViewController
@synthesize recipes;
@synthesize managedObjectContext;
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(@"View Did Load");
NSManagedObjectContext *context = [self managedObjectContext];
if (!context) {
NSLog(@"There is an error!!!");
}
if (context == nil) {
NSLog(@"Context is nil in viewController");
}
else {
NSLog(@"Context is set in viewController");
}
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
} else {
return YES;
}
}
- (void)viewDidUnload {
[super viewDidUnload];
}
@end
I know the NSManagedObjectContext is nil in my ViewController. The question is how do I pass my context from AppDelegate into ViewController? I don't want to have to question the AppDelegate from my viewControllers (More will hopefully be added) every time I want to query CoreData, I'm looking to pass the managedObjectContext around.
I hope that all makes sense. :)
I have discovered the answer to my issue. The managedObjectContext wasn't being passed correctly to my viewController.
I was using:
viewController.managedObjectContext = self.managedObjectContext;
When I should have been using:
ViewController *viewController = (ViewController *)self.window.rootViewController;
viewController.managedObjectContext = self.managedObjectContext;
Thanks user523234 for putting me on the right lines.
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