Question

我有一个简单的笔记项目，我只有2个控制器：

NotesListViewController
CreateNotesViewController

在prepareForSegue我的CreateNotesViewController方法中，我将note属性设置为TextView文本属性，而不是我在unwindToList方法中将其设置为NotesListViewController 1}}。

但是当我运行应用程序时，我在代码行中出现错误，我想将recieivedNote添加到我的notes数组（在NotesListViewController中）。

我的视图控制器很短，所以我希望你不介意我分享它们：（我也只是学习核心数据基础并试图在这里实现它，这可能会导致问题）

CreateNotesViewController.m：

#import "CreateNotesViewController.h"

@interface CreateNotesViewController ()

@property (weak, nonatomic) IBOutlet UIBarButtonItem *saveButton;
@property (weak, nonatomic) IBOutlet UITextView *myTextView;

@end


@implementation CreateNotesViewController


- (NSManagedObjectContext *) managedObjectContext
{
    NSManagedObjectContext *context = nil;

    id delegate = [[UIApplication sharedApplication] delegate];

    if ([delegate performSelector:@selector(managedObjectContext)]){
        context = [delegate managedObjectContext];
    }

    return context;
}


- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if (sender != self.saveButton) return;
    else if (self.myTextView.text.length > 0) {
        [self.note awakeFromInsert];

        self.note.content = self.myTextView.text;

        NSManagedObjectContext *context = [self managedObjectContext];

        // creating a new managed object
        NSManagedObject *newNote = [NSEntityDescription insertNewObjectForEntityForName:@"Note" inManagedObjectContext:context];

        [newNote setValue:self.myTextView.text forKey:@"content"];

        NSError *error = nil;

        if (![context save:&error]) {
            NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
        }
    }
}


- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    self.myTextView.text = self.note.content;

    // listen for keyboard hide/show notifications so we can properly adjust the table's height
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];

}


- (void)adjustViewForKeyboardReveal:(BOOL)showKeyboard notificationInfo:(NSDictionary *)notificationInfo
{
    // the keyboard is showing so ƒ the table's height
    CGRect keyboardRect = [[notificationInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    NSTimeInterval animationDuration =
    [[notificationInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
    CGRect frame = self.myTextView.frame;

    // the keyboard rect's width and height are reversed in landscape
    NSInteger adjustDelta = UIInterfaceOrientationIsPortrait(self.interfaceOrientation) ? CGRectGetHeight(keyboardRect) : CGRectGetWidth(keyboardRect);

    if (showKeyboard)
    frame.size.height -= adjustDelta;
    else
    frame.size.height += adjustDelta;

    [UIView beginAnimations:@"ResizeForKeyboard" context:nil];
    [UIView setAnimationDuration:animationDuration];
    self.myTextView.frame = frame;
    [UIView commitAnimations];
}



- (void)keyboardWillShow:(NSNotification *)aNotification
{
    [self adjustViewForKeyboardReveal:YES notificationInfo:[aNotification userInfo]];
}



- (void)keyboardWillHide:(NSNotification *)aNotification
{
    [self adjustViewForKeyboardReveal:NO notificationInfo:[aNotification userInfo]];
}


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


@end

NotesListViewController.m

#import "NotesListViewController.h"
#import "Note.h"
#import "CreateNotesViewController.h"

@interface NotesListViewController ()

@property (nonatomic, strong) NSMutableArray *notes;

@property (nonatomic) NSInteger editedRow;


@end

@implementation NotesListViewController

- (NSManagedObjectContext *) managedObjectContext
{
    NSManagedObjectContext *context = nil;

    id delegate = [[UIApplication sharedApplication] delegate];

    if ([delegate performSelector:@selector(managedObjectContext)]){
        context = [delegate managedObjectContext];
    }

    return context;
}


- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"editSegue"]) {
        CreateNotesViewController *destination = (CreateNotesViewController *)[segue destinationViewController];
        NSInteger indx = [self.tableView indexPathForCell:sender].row;
        Note *noteToPass = self.notes[indx];
        destination.note = noteToPass;
        self.editedRow = indx;
    } else if ([[segue identifier] isEqualToString:@"addSegue"]) {
        self.editedRow = -1;
    }
}


- (IBAction)unwindToList:(UIStoryboardSegue *)segue
{
    CreateNotesViewController *source = (CreateNotesViewController *)[segue sourceViewController];
    Note *recieivedNote = source.note;

    if (recieivedNote != nil && self.editedRow == -1) {
        [self.notes addObject:recieivedNote];
    } else {
//this is the line that i get the error in:

        [self.notes replaceObjectAtIndex:self.editedRow withObject:recieivedNote];
    }

    [self.tableView reloadData];
}


- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.notes = [[NSMutableArray alloc] init];
}

- (void) viewWillAppear
{
    NSManagedObjectContext *managedObjectContext = [self managedObjectContext];

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Note"];

    self.notes = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy];

    [self.tableView reloadData];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return self.notes.count;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    // Configure the cell...

    NSManagedObject *noteToDisplay = [self.notes objectAtIndex:indexPath.row];

    //Note *noteToDisplay = [self.notes objectAtIndex:indexPath.row];

    cell.textLabel.text = [noteToDisplay valueForKey:@"content"];

    return cell;
}



@end

Note.h（这是模型，.m文件中没有任何内容）

@interface Note : NSManagedObject

@property (nonatomic, retain) NSString * content;

@end

请帮我弄清楚为什么我传递一个零物品......

错误截图：

enter image description here

Answer 1

Nir，在您的NotesListViewController.m和prepareForSegue:sender:方法中，您包含以下代码行。

    destination.note = noteToPass;

据我了解，在这行代码中，您尝试在目标视图控制器note中设置属性CreateNotesViewController.m:，但属性note不存在。

查看包含note公共属性（在CreateNotesViewController.h中声明 - 以便它是公共的，即可由其他类访问，更重要的是可以访问NotesListViewController类）。您还需要导入Note.h。

CreateNotesViewController.h文件中的两行额外代码将包含类似的内容......

#import "Note.h"

和

@property (nonatomic, strong) Note *note;

然后当你＆＃34;设置＆＃34;代码行destination.note = noteToPass中的note属性，这样您就提供了一个公共属性来接收noteToPass的值。

这有帮助吗？

无法将对象数据传递给第二个视图控制器

1 个答案: