小编ves*_*ead的帖子

我无法弄清楚为什么这段代码很糟糕.我认为在dictionaryWithObjectsAndKeys中使用静态字符串是可以的,但它在运行时因EXC_BAD_ACCESS而失败.我使用调试器来识别它在定义行中实际上是失败的.它永远不会输出"Made it here".

- (NSString *)polyName:(NSUInteger)vertices { 
    NSLog(@"looking for polyName with %d vertices.", vertices);

    NSDictionary *polNameDict = [NSDictionary dictionaryWithObjectsAndKeys:
                             @"triangle", @"3", 
                             @"square", @"4",
                             @"pentagon","5",
                             @"Hexagon", @"6",
                             @"Heptagon", @"7",
                             @"Octagon", @"8",
                             @"Nonagon", @"9",
                             @"Decagon", @"10",
                             @"Hendecagon", @"11",
                             @"Dodecagon", @"12",
                             nil];

   NSLog(@"Made it here");

   NSString *key = [NSString stringWithFormat: @"%d", vertices]; 
   NSString *polName = [polNameDict objectForKey:key];
   return (polName);
   // Memory management: No need to release polNameDict, key, polName because they use
   // convenience functions
} 

我从NavigationViewController模板开始我的xcode项目.现在,当我按下视图时,该视图默认情况下会出现一个编辑按钮而没有后退按钮.我已经注释掉editButton代码和相应的setEditing委托方法.但是我无法显示后退按钮.我究竟做错了什么？

推动新视图:

PlaylistViewController *playlistViewController = [[PlaylistViewController alloc] init];
playlistViewController.managedObjectContext = self.managedObjectContext;

[self.navigationController pushViewController:playlistViewController animated:YES];
[playlistViewController release];

在我的PlaylistViewController中:

- (void)viewDidLoad {
    [super viewDidLoad];

    self.title = @"";

    // self.navigationItem.leftBarButtonItem = self.editButtonItem;

    // doesn't matter if this is here or not
    self.navigationItem.hidesBackButton = false;

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