iphone - 如何正确释放带有 NSMutableArray 成员且内部有 NSNumber 对象的对象的 NSMutableArray？

Question

我对 iOS 内存管理感到困惑。我有一个类，它有一个 NSMutableArray 类型的成员。当将这种类型的对象存储在另一个数组中并删除它们时，Instruments 显示所有这些成员都会泄漏内存。这是我的流氓类的定义:

@interface Tester : NSObject {
  int some;
  NSMutableArray* others;
}
@property int some;
@property (nonatomic, retain) NSMutableArray* others;
-(id)init;
-(id)copy;
-(void)dealloc;
@end

这是流氓类的实现:

@implementation Tester

@synthesize some;
@synthesize others;

-(id)init {
  self = [super init];
  if(self) {
    some = 0;
    others = [[NSMutableArray alloc] initWithCapacity:5];
    int i;
    for(i = 0; i < 5; ++i) {
      [others addObject:[NSNumber numberWithInt:i]];
    }
  }
  return self;
}

-(id)copy {
  Tester* cop = [[Tester alloc] init];
  cop.some = some;
  cop.others = [others mutableCopy]
  return cop;
}

-(void)dealloc {
  [others removeAllObjects];
  [others release];
  [super dealloc];
}
@end

这是我测试它的方法:

NSMutableArray* container = [[NSMutableArray alloc] init];
Tester* orig = [[Tester alloc] init];
int i;
for(i = 0; i < 10000; ++i) {
  Tester* cop = [orig copy];
  [container addObject:cop];
}
while([container count] > 0) {
  [[container lastObject] release];
  [container removeLastObject];
}
[container release];

运行此代码会泄漏内存，并且 Instruments 显示泄漏的内存是在以下行分配的:

cop.others = [others mutableCopy];

我做错了什么？

Answer 1

您正在创建一个副本:[others mutableCopy]，您拥有该副本但忘记释放。该行应该是:

cop.others = [[others mutableCopy] autorelease];

如果您让 container 数组成为 Tester 对象的唯一所有者，您的测试代码将会更加清晰:

NSMutableArray* container = [[NSMutableArray alloc] init];
Tester* orig = [[Tester alloc] init];
for (int i = 0; i < 10000; ++i)
    [container addObject:[[orig copy] autorelease]];

while([container count] > 0)
    [container removeLastObject];

[container release];

现在您可以删除清空容器的循环。

或者你可以跳过容器:

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

Tester* orig = [[[Tester alloc] init] autorelease];
for (int i = 0; i < 10000; ++i)
    [[orig copy] autorelease];

[pool drain]; // At this point all Tester objects are released