我有一个表 View Controller 和一个 View Controller 。
HomeViewController 标签应始终显示 StackTableViewController 的第一个标记。
我需要确定是否删除了第一个字符串以显示新的第一个字符串。
这就是我遇到问题的地方......如果我删除第一个字符串并返回到 HomeViewController，标签仍然是我刚刚删除的字符串......如果我终止应用程序并再次打开它，正确的标签中显示的字符串。
到目前为止，我是这样做的:
这是我的 StackTableViewController.h + .m 中的相关方法:
@protocol StackTableViewControllerDelegate <NSObject>
@optional
-(void)didDeleteObject;
@end
@interface StackTableViewController : UITableViewController <UITableViewDataSource,UITableViewDelegate>
@property (strong,nonatomic) id<StackTableViewControllerDelegate> delegate;
@property (strong, nonatomic) NSString *currentTarget;
@end
#import "StackTableViewController.h"
#import "Target.h"
#import "StackTableViewCell.h"
#import "HomeViewController.h"
#import "CoreDataStack.h"
@interface StackTableViewController () <NSFetchedResultsControllerDelegate>
@property (nonatomic, strong) NSFetchedResultsController *fetchedResultController;
@end
@implementation StackTableViewController
- (id)init {
self = [super initWithNibName:@"StackTableViewController" bundle:nil];
if (self) {
// Do something
[self.fetchedResultController performFetch:nil];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
Target *current = [self.fetchedResultController objectAtIndexPath:indexPath];
self.currentTarget = current.body;
}
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
self.navigationItem.rightBarButtonItem = self.editButtonItem;
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
Target *current = [self.fetchedResultController objectAtIndexPath:indexPath];
self.currentTarget = current.body;
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
Target *target = [self.fetchedResultController objectAtIndexPath:indexPath];
CoreDataStack *stack = [CoreDataStack defaultStack];
[[stack managedObjectContext] deleteObject:target];
[stack saveContext];
if ([_delegate respondsToSelector:@selector(didDeleteObject)]) {
[_delegate didDeleteObject];
}
}
这是 HomeViewController.h + .m 中的相关方法:
#import <UIKit/UIKit.h>
#import "StackTableViewController.h"
@interface HomeViewController : UIViewController {
StackTableViewController *stackTableViewController;
}
@property (strong, nonatomic) IBOutlet UILabel *homeLabel;
- (IBAction)goToStack:(id)sender;
#import "StackTableViewController.h"
@interface HomeViewController () <StackTableViewControllerDelegate>
@end
@implementation HomeViewController
- (id)init {
self = [super initWithNibName:@"HomeViewController" bundle:nil];
if (self) {
// Do something
stackTableViewController = [[StackTableViewController alloc] init];
stackTableViewController.delegate = self;
}
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
[self.navigationController setNavigationBarHidden:YES];
self.homeLabel.font = [UIFont fontWithName:@"Candara-Bold" size:40];
self.homeLabel.text = stackTableViewController.currentTarget;
}
- (void)didDeleteObject {
self.homeLabel.text = stackTableViewController.currentTarget;
}
- (IBAction)goToStack:(id)sender {
StackTableViewController *vc = [[StackTableViewController alloc] init];
[self.navigationController pushViewController:vc animated:YES];
}
CoreDataStack.h +.m:
#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
#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 onceTocken;
dispatch_once (&onceTocken, ^{
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.Treats" 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:@"Treats" 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:@"Treats.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();
}
}
}
@end
请帮我解决这个问题，我想了很多办法，但可能我遗漏了一些与 View Controller 生命周期有关的东西。
(CoreDataStack 是一个单例)
天啊!!
最佳答案
您可以做的是使用一个 Action 来检查发件人和 segue 以了解它来自哪里:
- (void)unwindFromModal:(UIStoryboardSegue *)unwindSegue {
if unwindSegue.identifier == @"createModal" {
NSLog(@"Got home from create page");
}
if unwindSegue.identifier == @"stackModal" {
NSLog(@"Got home from stack page");
}
}
- (IBAction)presentModal:(UIButton*)sender {
if sender.tag == 0 {
[self performSegueWithIdentifier:@"createModal" sender:self];
}
if sender.tag == 1 {
[self performSegueWithIdentifier:@"stackModal" sender:self];
}
}
你可以在标签中使用字符串常量来提高可读性，如果你愿意的话也可以切换
关于ios - 我应该如何正确执行此委托(delegate)？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/27203474/