当视图出现时在表格中加载新数据

Question

在我的项目中，我有一个用于以类似于地址簿应用程序的方式添加/显示/编辑联系人的机制。我使用核心数据进行数据管理。基本上，当应用程序加载时，我所有的当前联系人都在那里，但是当我添加一个新联系人并返回到所有联系人的表视图时，我看不到更改。然后，当我关闭应用程序并再次打开它时，可以看到更改。有人可以让我知道我做错了什么吗？我想在添加新联系人后刷新它。

allathletes.m

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    UIBarButtonItem *addButton = [[UIBarButtonItem alloc] 
            initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addAthlete)]; 
    self.navigationItem.rightBarButtonItem = addButton; 

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; 
    _managedObjectContext = [appDelegate managedObjectContext]; 

    NSFetchRequest *request = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *athlete = [NSEntityDescription entityForName:@"Athlete" inManagedObjectContext:_managedObjectContext]; 
    [request setEntity:athlete]; 
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"first" ascending:YES]; 
    NSArray *sortDescriptors = [[NSArray alloc]initWithObjects:sortDescriptor, nil]; 
    [request setSortDescriptors:sortDescriptors]; 

    NSError *error = nil; 
    NSMutableArray *mutableFetchResults = [[_managedObjectContext executeFetchRequest:request error:&error] mutableCopy]; 
    if (mutableFetchResults == nil){ 
     //handle error 
    } 
    [self setAthleteArray:mutableFetchResults]; 


    // 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)addAthlete{ 
    AthleteAdd *addAthlete= [self.storyboard instantiateViewControllerWithIdentifier:@"addAthlete"]; 
    [self.navigationController pushViewController:addAthlete animated:YES]; 
} 

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

    Athlete *athlete = (Athlete *)[athleteArray objectAtIndex:indexPath.row]; 
    cell.textLabel.text = [athlete first]; 
    cell.detailTextLabel.text = [athlete last]; 
    // Configure the cell... 

    return cell; 
} 

addathlete.m

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    AppDelegate *appDelegate = [[UIApplication sharedApplication]delegate]; 
    _managedObjectContext = [appDelegate managedObjectContext]; 

    UIBarButtonItem *saveButton=[[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:self action:@selector(saveAthlete)]; 
    UIBarButtonItem *cancelButton=[[UIBarButtonItem alloc] initWithTitle:@"Cancel" style:UIBarButtonItemStyleDone target:self action:@selector(cancelSave)]; 
    self.navigationItem.rightBarButtonItem = saveButton; 
    self.navigationItem.leftBarButtonItem = cancelButton; 
} 

-(void)saveAthlete{ 
    Athlete *athlete = [NSEntityDescription insertNewObjectForEntityForName:@"Athlete" inManagedObjectContext:_managedObjectContext]; 
    [athlete setFirst:firstTextField.text]; 
    [athlete setLast:lastTextField.text]; 

    NSError *error = nil; 
    if(![_managedObjectContext save:&error]){ 
     //handle dat error 
    } 
    [[self navigationController] popViewControllerAnimated:YES]; 
} 

-(void)cancelSave{ 

    [[self navigationController] popViewControllerAnimated:YES]; 

} 

Answer 1

新的运动员被添加到持久性存储，但你的表没有显示你更新的数据。添加新的运动员对象后，从持久性存储获取更新的数据到AthleteArray（步骤1）并重新载入您的表格视图（步骤2）。

步骤1：

AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; 
    _managedObjectContext = [appDelegate managedObjectContext]; 

    NSFetchRequest *request = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *athlete = [NSEntityDescription entityForName:@"Athlete" inManagedObjectContext:_managedObjectContext]; 
    [request setEntity:athlete]; 
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"first" ascending:YES]; 
    NSArray *sortDescriptors = [[NSArray alloc]initWithObjects:sortDescriptor, nil]; 
    [request setSortDescriptors:sortDescriptors]; 

    NSError *error = nil; 
    NSMutableArray *mutableFetchResults = [[_managedObjectContext executeFetchRequest:request error:&error] mutableCopy]; 
    if (mutableFetchResults == nil){ 
     //handle error 
    } 
    [self setAthleteArray:mutableFetchResults]; 

步骤2：

[self.tableView reloadData]; 

Answer 2

重载的tabelView在viewDidAppear: OR viewWillAppear:方法。在pop和dismiss时，viewDidLoad:方法不会呼叫。这就是为什么更新在tableView中不可见的原因。