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Created December 8, 2011 16:12
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ARC環境下でのメモリの振る舞い
//定義
@implementation TestDestructor
- (id)init{
self = [super init];
NSLog(@"a");
return self;
}
- (void)dealloc{
NSLog(@"b");
}
@end
//実行
{
TestDestructor *test = [[TestDestructor alloc] init];
NSLog(@"c");
}
NSLog(@"d");
//実行結果
2011-12-09 01:07:30.627 ARC[626:f803] a
2011-12-09 01:07:30.631 ARC[626:f803] c
2011-12-09 01:07:30.633 ARC[626:f803] b
2011-12-09 01:07:30.635 ARC[626:f803] d
//例外時はどうなるか?
//test
{
TestDestructor *test = [[TestDestructor alloc] init];
@throw [NSException exceptionWithName:@"test" reason:nil userInfo:nil];
NSLog(@"c");
}
NSLog(@"d");
//実行結果
2011-12-09 01:56:11.638 ARC[722:f803] a
2011-12-09 01:56:11.642 ARC[722:f803] test
//つまりブロックを抜けているが、deallocは呼ばれない
//autoreleaseとの比較
//実行
{
TestDestructor *test = [[[TestDestructor alloc] init] autorelease];
NSLog(@"c");
}
NSLog(@"d");
//実行結果
2011-12-09 02:06:58.084 Sample[843:f803] a
2011-12-09 02:06:58.086 Sample[843:f803] c
2011-12-09 02:06:58.087 Sample[843:f803] d
2011-12-09 02:06:58.092 Sample[843:f803] b
//デストラクタというよりもファイナライザ的な解放処理
//エラー時
2011-12-09 02:17:54.364 Sample[924:f803] a
2011-12-09 02:17:54.367 Sample[924:f803] test
2011-12-09 02:17:54.368 Sample[924:f803] b
//autopool releaseのときにメモリ回収は可能
//ARC環境下では例外ジャンプが@autoreleasepoolブロック内でも回収されなかった。この辺りがC++のデストラクタの挙動と異なる
//C++で同等のコードを書いたとき
class CppDestructor
{
public:
CppDestructor(){
NSLog(@"a");
}
~CppDestructor(){
NSLog(@"b");
}
void test(){
}
};
{
CppDestructor test;
@throw [NSException exceptionWithName:@"test" reason:nil userInfo:nil];
NSLog(@"c");
}
NSLog(@"d");
2011-12-09 02:33:56.531 Sample[1121:f803] a
2011-12-09 02:33:56.535 Sample[1121:f803] b
2011-12-09 02:33:56.536 Sample[1121:f803] test
//例外でスコープを抜けた時点でデストラクタが呼ばれる
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