iphone releas 后retatincount 为1

bo_xiaozhao

于 2011-07-25 17:34:23 发布

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分类专栏：问题整理文章标签：移动开发

本文链接：https://blog.youkuaiyun.com/bo_xiaozhao/article/details/83976118

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本文通过一个简单的测试程序探讨了Objective-C中retain/release方法的工作原理。预期对象在被释放后保留计数应减至0并被释放，但实验结果显示保留计数在第一次释放后仍为1。文章解释了这是由于当对象的保留计数为1时，再进行释放操作将直接导致对象被销毁，而非递减至0，这是一种实现上的优化。

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I created a simple program to test the retain/release methods in Objective-C memory management. As I understand of ObjC memory management, I expect that a object with retain count = 1 on which I callrelease get the retain count decremented to zero and then released. But this test program show that after the first release I still get retain count = 1:

// TestClass.h
#import <Cocoa/Cocoa.h>
@interface TestClass : NSObject {
}
@end

// TestClass.m
#import "TestClass.h"
@implementation TestClass
@end

// RetainRelease.m
#import <Foundation/Foundation.h>
#include "TestClass.h"

void dumpRetain(id o);

int main (int argc, const char * argv[]) {
    TestClass *s = [[TestClass alloc] init];
    dumpRetain(s);

    [s release];
    dumpRetain(s);
}

2010-08-13 17:42:45.489 RetainRelease[20933:a0f] NSString - retain count=1
2010-08-13 17:42:45.491 RetainRelease[20933:a0f] NSString - retain count=1

答案：

it's implemented as "when the object is released with a retainCount of 1, it's deallocated", because there's no need to ever decrement it to 0. It's an implementation optimization.