iphone - Xcode 的 "build and analyze"报告此代码存在奇怪的内存泄漏

Question

有谁知道为什么 xCode 的“构建和分析”会将此行报告为“可能的内存泄漏”？

goodSound = [[SoundClass alloc] initializeSound:@"Good.wav"];

/////以下是有问题的 4 个文件:

//  Sounds.h 

#import <Foundation/Foundation.h> 
#import <AudioToolbox/AudioToolbox.h> 

@interface SoundClass : NSObject  
{ 
    SystemSoundID soundHandle; 
} 

-(id) initializeSound:(NSString *)soundFileName; 
-(void) play;    

@end 

//////////////

//  Sounds.m 

#import "Sounds.h" 

@implementation SoundClass 

-(id) initializeSound:(NSString *)soundFileName 
{ 
    self = [super init]; 

    NSString *const resourceDir = [[NSBundle mainBundle] resourcePath]; 
    NSString *const fullPath    = [resourceDir stringByAppendingPathComponent:soundFileName]; 
    NSURL *const url            = [NSURL fileURLWithPath:fullPath]; 

    OSStatus errCode = AudioServicesCreateSystemSoundID((CFURLRef) url, &soundHandle); 

    if(errCode == 0) 
        NSLog(@"Loaded sound: %@", soundFileName); 
    else 
        NSLog(@"Failed to load sound: %@", soundFileName); 

    return self;             
} 

////////////////////////////// 

-(void) play     
{ 
    AudioServicesPlaySystemSound(soundHandle); 
} 

///////////////////////////// 

-(void) dealloc 
{ 
    AudioServicesDisposeSystemSoundID(soundHandle); 
    [super dealloc]; 
} 

///////////////////////////// 

@end 

///////////////

//  MemTestViewController.h 

#import <UIKit/UIKit.h> 

@class SoundClass; 

@interface MemTestViewController : UIViewController  
{ 
    SoundClass *goodSound; 
} 

-(IBAction) beepButtonClicked:(id)sender; 

@end 

///////////

//  MemTestViewController.m 

#import "MemTestViewController.h" 
#import "Sounds.h" 

@implementation MemTestViewController 

- (void)viewDidLoad  
{ 
    NSLog(@"view did load: alloc'ing mem for sound class"); 

    // "build and analyze" says this is possibly a memory leak: 
    goodSound = [[SoundClass alloc] initializeSound:@"Good.wav"]; 

    [super viewDidLoad]; 
} 


-(IBAction) beepButtonClicked:(id)sender 
{ 
    NSLog(@"beep button clicked"); 

    [goodSound play]; 
} 


- (void)didReceiveMemoryWarning  
{ 
    [super didReceiveMemoryWarning]; 
} 


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

@end 

Answer 1

这可能是内存泄漏。如果 View 被卸载，viewDidLoad 可能会被调用任意多次，在这种情况下，每次都会泄漏内存。为了进行保护，您可以释放 viewDidUnload 中的内存并将 ivar 设置为 nil，或者仅当 ivar 实际上为 nil 时才在 viewDidLoad 中初始化声音。

所以:

- (void)viewDidLoad
{
  if( !goodSound )
    goodSound = [[SoundClass alloc] initializeSound:@"Good.wav"];
  [super viewDidLoad];
}

和/或:

- (void)viewDidUnload
{
  [goodSound release];
  goodSound = nil;
  [super viewDidUnload];
}