-(无效)dealloc问题

Question

你能告诉我以下代码是否100%正确吗？特别是dealloc部分

FirstViewController.h

#import <UIKit/UIKit.h>
#import "SecondViewController.h"

@class SecondViewController

@interface FirstViewController : UIViewController
{
    SecondViewController   *SecondController;
}

- (IBAction)SwitchView;

@property (nonatomic, retain) IBOutlet SecondViewController *SecondController;

@end

FirstViewController.m

#import "FirstViewController.h"

@implementation FirstViewController

@synthesize SecondController;

- (IBAction)SwitchView
{    
    SecondController = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
    SecondController.modalTransitionStyle = UIModalPresentationFullScreen;
    [self presentModalViewController:SecondController animated:YES];
    [SecondController release];
}

/// OTHER CODE HERE ///

- (void)dealloc
{
    [SecondController release];
    [super dealloc];
}

@end

谢谢!

Answer 1

不不对。您将release消息发送到dealloc中的指针，但是指针可能指向SecondController，也可能不再指向SecondController。这可能会导致一些非常奇怪的错误，通常是随机对象被释放。

在objective术语中，您的类不保留(考虑“属于”) SecondController，所以它不应该首先在dealloc上发布它。

要以正确的方式主张和释放所有权，请这样做：

- (IBAction)SwitchView
{    
    self.SecondController = [[[SecondViewController alloc] 
                  initWithNibName:@"SecondViewController" bundle:nil] autorelease];
    self.SecondController.modalTransitionStyle = UIModalPresentationFullScreen;
    [self presentModalViewController:self.SecondController animated:YES];
}

/// OTHER CODE HERE ///

- (void)dealloc
{
    self.SecondController = nil;
    [super dealloc];
}

这还将保护您免受SwitchView和dealloc之间发生的任何其他事情的影响。(只要这些内容遵循规则，并使用self.SecondController = ...更改属性)

在SwitchView中，alloc/autorelease序列使您的例程保留例程长度的所有权(并且稍微超出)。self.SecondController =部件确保类保留了SecondController对象，因为您声明了它为(nonatomic,retain)。

Answer 2

您应该使用属性设置器来分配SecondController。

我建议您只使用alloc/init视图控制器一次，然后在SwitchView中显示它：

#import "FirstViewController.h"

@implementation FirstViewController

- (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle {
   if((self = [super initWithNibName:nibName bundle:nibBundle])) {
      self.SecondController = [[[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil] autorelease];
      SecondController.modalTransitionStyle = UIModalPresentationFullScreen;
   }
   return self;
}

- (IBAction)SwitchView
{    
    [self presentModalViewController:SecondController animated:YES];
}

/// OTHER CODE HERE ///

- (void)dealloc
{
    [SecondController release];
    [super dealloc];
}

@end

这样，您实际上只创建SecondController视图控制器一次，而不是每次调用-SwitchView时都创建它。