断言失败第二次添加/删除

Question

我有一个奇怪的问题：我在一个包含按钮的 SplitViewController 中有一个 DetailViewController。这个按钮有一个到 NavigationController 和 UITableViewController 的 Popover segue，它充当记事本。我第一次打开弹出窗口时，记事本效果很好，正如预期的那样。但是，如果我关闭弹出框然后重新打开它，添加或删除注释时它会失败。应用重启后功能恢复。

添加代码归咎：

[_objects insertObject:newNote atIndex:0];

删除被指责的代码：

[_objects removeObjectAtIndex:indexPath.row];

几乎整个 NotesViewController.m 类：

#import "NotesTableViewController.h"

@interface NotesTableViewController ()
{
NSMutableArray *_objects;
BOOL firstRun;
}

@end

@implementation NotesTableViewController
@synthesize openSubject;

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

- (void)awakeFromNib
{
self.clearsSelectionOnViewWillAppear = NO;
self.preferredContentSize = CGSizeMake(320.0, 600.0);
[super awakeFromNib];
}

- (void)viewDidLoad
{
[super viewDidLoad];

// Load the notes data
// Create the key
NSString *partOfKey = @"-notes";
NSString *notesKey = [NSString stringWithFormat:@"%@%@", openSubject, partOfKey];

// Do any additional setup after loading the view, typically from a nib
self.navigationItem.leftBarButtonItem = self.editButtonItem;

// Register a class or nib file using registerNib:forCellReuseIdentifier
// o registerClass:forCellReuiseIdentifier: method before calling this method
[self.tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"Cell"];

// Load the _objects from NSUserdefaults
_objects = nil;
_objects = [[NSUserDefaults standardUserDefaults] objectForKey:notesKey];

if (openSubject.length == 0) {
    // There's currently no subject open, write it in the navigationbar
    // Prompt = open subject
    // Title = notes header
    self.navigationItem.prompt = @"No subject selected";
    self.navigationItem.title = @"My Notes";
} else {
    // Open the subject

    // Prompt = notes header
    // Title = open subject
    self.navigationItem.prompt = openSubject;
    self.navigationItem.title = @"My notes";
}

// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;
}



- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)addNote:(id)sender {
// Create a new note
if (openSubject.length == 0) {
    // The openSubject is nil, can't add a subject - tell the user
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"No subject" message: @"Please select a subject prior to adding a note" delegate: nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show];
} else {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"New note" message:@"Enter a note" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"Add", nil];
    alert.alertViewStyle = UIAlertViewStylePlainTextInput;
    [alert show];
}
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
// The user created a new subject, add it
if (buttonIndex == 1) {
    // Get the input text
    NSString *newNote = [[alertView textFieldAtIndex:0] text];

    // Check if the note already exist
    if ([_objects containsObject:newNote]) {
        // Tell the user this note already exists
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Already exists" message: @"This note already exist, sorry" delegate: nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
    } else {
        // The note doesn't exist, add it
        // Initialize objects
        if (!_objects) {
            _objects = [[NSMutableArray alloc] init];
        }

        // Add
        [_objects insertObject:newNote atIndex:0];
        NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
        [self.tableView insertRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];

        // Save the new _objects
        [self saveObjects];
    }
}
}

-(void)saveObjects {
// Create the key
NSString *partOfKey = @"-notes";

    // Save the new objects
NSString *notesKey = [NSString stringWithFormat:@"%@%@", openSubject, partOfKey];
[[NSUserDefaults standardUserDefaults] setObject:_objects forKey:notesKey];
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
#warning Potentially incomplete method implementation.
// Return the number of sections.
return 1;
}

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

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

if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}

NSString *object = _objects[indexPath.row];
cell.textLabel.text = [object description];
return cell;
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
    [_objects removeObjectAtIndex:indexPath.row];
    [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
}

调试器输出：

2014-05-21 20:43:14.564 myApp[263:60b] viewDidAppear 2014-05-21 20:43:15.093 myApp [263:60b] viewDidAppear 2014-05-21 20:43:29.741 myApp[263:60b] * 由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因：“-[__NSCFArray insertObject:atIndex:]: 发送到不可变对象的变异方法” * 首先抛出调用栈： （0x2d95bfd3 0x38440ccf 0x2d95bf15 0x2d8cfa93 0xf6e29 0x3038eb29 0x3038e7fb 0x3029605f 0x30348377 0x301f76f5 0x3017055b 0x2d9272a5 0x2d924c49 0x2d924f8b 0x2d88ff0f 0x2d88fcf3 0x32789663 0x301db16d 0xf9411 0x3894dab7） libc++abi.dylib：以 NSException 类型的未捕获异常终止 (lldb)

请帮我解决这个问题，我不知道。

提前致谢

Answer 1

当您从 NSUserDefaults 取回数组时，它会返回一个不可变数组。您需要获取 mutableCopy 或执行 _objects = [NSMutableArray arrayWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:notesKey]];

Here's a link of this answered