Question

我有一个自定义对象类（Ship.h和Ship.m），我正在尝试使用以下代码创建一个新的Ship类型对象：

Ship *PlayerShip = [[Ship alloc] init];

代码目前在我的第一个视图controller.m和

下

- (void)viewDidLoad{

但我在

中尝试过

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

。

我没有问题就创建了PlayerShip对象，然后用

进行记录

NSLog(@"Player ship: %@",PlayerShip);

它也记录得很好。

然后在我的代码的另一部分（除了我放置的地方之外的任何地方），例如NSTimer我尝试相同的NSLog行并返回

玩家发货：无效

PlayerShip对象是否因某种原因被删除？

我将不胜感激。

下面是我的shipViewController.h

#import <UIKit/UIKit.h>
#import "Ship.h"
@interface ShipViewController : UIViewController{
IBOutlet UILabel *PlayerShipLabel;
IBOutlet UIProgressView *PlayerHullBar;
IBOutlet UIProgressView *PlayerShieldBar;
IBOutlet UILabel *PlayerCreditsLabel;
IBOutlet UIImageView *PlayerShipImage;
IBOutlet UIButton *PlayerRepairBreachButton;
}


@end
Ship *PlayerShip;

这是ShipViewController.m

#import "ShipViewController.h"

@interface ShipViewController ()

@end

@implementation ShipViewController

- (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.
    Ship *PlayerShip = [[Ship alloc] init];
    NSLog(@"Player ship: %@",PlayerShip);
}



- (IBAction)ShieldSwitch:(id)sender {
    NSLog(@"Ship is %@ ",PlayerShip);

}

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

/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/

@end

以下是应用程序首次启动时程序的输出：

2014-06-12 19:02:27.503 First Game[5193:60b] Created a new ship!
2014-06-12 19:02:27.504 First Game[5193:60b] Player ship: <Ship: 0x8c30f70>

这是我按下按钮验证PlayerShip的输出：

2014-06-12 19:02:29.472 First Game[5193:60b] Ship is (null)

Answer 1

有几个问题。

为什么在 Ship *PlayerShip;声明之后在.h文件中声明@end？这使它成为一个全局变量。使其成为与其他变量类似的实例变量，但将其置于@interface语句的大括号中。

在viewDidLoad中，您创建一个与（即将成为）实例变量同名的局部变量。不要声明一个新变量。只需将新对象分配给（即将成为）实例变量。

在object为alloc和init之后，对象指针设置为null

1 个答案: