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我正在创建一个利用核心数据的应用程序。我正在添加自定义表格视图单元格并保存它们的顺序。我已经为一个表视图做了这个。但是，我有多个表视图，我不知道要更改代码以使其适用于其他表视图。我有一个名为 device 的实体的数据模型。它有一个名为'name'的字符串。我需要知道如何编辑代码以使其与其他表视图兼容我的代码如下。设备视图控制器.m：

@interface DeviceViewController ()
@property (strong) NSMutableArray *devices;
@end

@implementation DeviceViewController

- (NSManagedObjectContext *)managedObjectContext {
    NSManagedObjectContext *context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if ([delegate performSelector:@selector(managedObjectContext)]) {
    context = [delegate managedObjectContext];
}
return context;
}

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

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

// Uncomment the following line to display an Edit button in the navigation bar for this    view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

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

// Fetch the devices from persistent data store
NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Device"];
self.devices = [[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 the number of sections.
return 1;
}

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

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

// Configure the cell...
NSManagedObject *device = [self.devices objectAtIndex:indexPath.row];
[cell.textLabel setText:[NSString stringWithFormat:@"%@ ", [device valueForKey:@"name"]]];

return cell;
}


- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the specified item to be editable.
return YES;
}


- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
NSManagedObjectContext *context = [self managedObjectContext];

if (editingStyle == UITableViewCellEditingStyleDelete) {
    // Delete object from database
    [context deleteObject:[self.devices objectAtIndex:indexPath.row]];

    NSError *error = nil;
    if (![context save:&error]) {
        NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);
        return;
    }

    // Remove device from table view
    [self.devices removeObjectAtIndex:indexPath.row];
    [self. tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
}
}

#pragma mark - Table view delegate




 #pragma mark - Segue

 - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:@"UpdateDevice"]) {
    NSManagedObject *selectedDevice = [self.devices objectAtIndex:[[self.tableView indexPathForSelectedRow] row]];
    DeviceDetailViewController *destViewController = segue.destinationViewController;
    destViewController.device = selectedDevice;
}
}

@end

DeviceDetailViewController.m:

@interface DeviceDetailViewController ()

@end

@implementation DeviceDetailViewController
@synthesize device;

- (NSManagedObjectContext *)managedObjectContext {
NSManagedObjectContext *context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if ([delegate performSelector:@selector(managedObjectContext)]) {
    context = [delegate managedObjectContext];
}
return context;
}

- (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.
if (self.device) {
    [self.nameTextField setText:[self.device valueForKey:@"name"]];

}

}

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

- (IBAction)cancel:(id)sender {
[self dismissViewControllerAnimated:YES completion:nil];
}

- (IBAction)save:(id)sender {
NSManagedObjectContext *context = [self managedObjectContext];

if (self.device) {
    // Update existing device
    [self.device setValue:self.nameTextField.text forKey:@"name"];


} else {
    // Create a new device
    NSManagedObject *newDevice = [NSEntityDescription   insertNewObjectForEntityForName:@"Device" inManagedObjectContext:context];
    [newDevice setValue:self.nameTextField.text forKey:@"name"];

}

NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
    NSLog(@"Can't Save! %@ %@", error, [error localizedDescription]);
}

[self dismissViewControllerAnimated:YES completion:nil];
}
@end
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1 回答 1

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  • 用您需要的实体名称替换实体名称。
  • 相应地替换该实体的类类型。
  • 用适当的属性名称替换属性名称。
  • 确保详细视图控制器的对象属性是正确的类型。
  • 在详细视图控制器中也更改上述内容。

顺便说一句，您不需要一直重复创建托管对象上下文的代码。如果你有一个对象，你可以通过对象进入上下文（就像你在细节视图中所做的那样）：

NSManagedObjectContext *context = device.managedObjectContext;
于 2013-06-24T14:55:01.407 回答