将对象设置为nil时，不会调用dealloc方法
我有个问题。
我首先创build了一个扩展NSObject的对象，我提供了覆盖描述和dealloc方法。 这是我的Employee.m文件：
@implementation Employee ..... -(NSString *)description { return [NSString stringWithFormat:@"Employ ID: %d has $%d value of assets", [self employeeID], [self valueOfAssets]]; } -(void)dealloc { NSLog(@"deallocating.. %@", self); [super dealloc]; } 在我的main.m中，我首先创build了一个NSMutableArray来存放Employee对象列表：
NSMutableArray *employees = [[NSMutableArray alloc] init]; for (int i =0; i< 10; i++) { // Create an instance of Employee Employee *person = [[Employee alloc] init]; // Give the instance varaible interesting values [person setEmployeeID:i]; [employees addObject: person]; }
最后我把员工设置为零
employees = nil;
我期望每个Employee对象的dealloc方法被调用，我会看到一些日志，如：
deallocating.. Employ ID 0 has value..... deallocating.. Employ ID 2 has value..... ....
但是，我没有看到任何日志，如果我在dealloc方法上设置了一个断点，断点永远不会被命中。
有什么想法吗？
几点意见：
-
person = nil不会在非ARC代码中释放对象。 它将在ARC代码（至less如果它是强大的）。 -
在ARC中，本地对象在超出范围时将自动为您释放。 在非ARC中，超出范围的对象将不会被释放（如果您没有其他地方的其他对象的引用，则最终会发生泄漏）。
-
将项目添加到可变数组将增加项目的保留计数，因此即使在非ARC代码中包含发布，对象也不会被释放，直到保留计数降至零（不仅通过释放在将对象添加到数组之后，该对象会将其从数组中移除。
因此，鉴于这是非ARC代码，它可能是这样的：
- (void)testInNonArcCode { NSMutableArray *employees = [[NSMutableArray alloc] init]; // employees retain count = +1 for (int i =0; i< 10; i++) { //create an instance of Employee Employee *person = [[Employee alloc] init]; // person retain count = +1 //Give the instance varaible interesting values [person setEmployeeID:i]; [employees addObject: person]; // person retain count = +2 [person release]; // person retain count = +1 (YOU REALLY WANT TO DO THIS OR ELSE OR NON-ARC PROGRAM WILL LEAK) // person = nil; // this does nothing, except clears the local var that's limited to the for loop scope ... it does nothing to reduce the retain count or improve memory management in non-ARC code, thus I have commented it out } // do whatever you want [employees removeAllObjects]; // this will remove all of the person objects and they will have their respective retain counts reduced to 0, and therefore the Employee objects will be released [employees release]; // employees array's own retain count reduced to zero (and will now be dealloced, itself) }
在ARC代码中：
- (void)testInArcCode { NSMutableArray *employees = [[NSMutableArray alloc] init]; // employees retain count = +1 for (int i =0; i< 10; i++) { //create an instance of Employee Employee *person = [[Employee alloc] init]; // person retain count = +1 //Give the instance varaible interesting values [person setEmployeeID:i]; [employees addObject: person]; // person retain count = +2 // person = nil; // this would reduce person retain count to +1 (but unnecessary in ARC because when person falls out of scope, it will have it's retain count automatically reduced) } // do whatever you want [employees removeAllObjects]; // this will remove all of the person objects and they will have their respective retain counts reduced to 0, and therefore will be released // [employees release]; // not permitted in ARC // employees = nil; // this would effectively release employees, but again, not needed, because when it falls out of scope, it will be released anyway }
释放物体的正确方法是做
[employees release];
将其设置nil将不会释放内存。
由于你被允许调用[super dealloc] ，我可以假设你没有使用自动引用计数 。 这意味着你需要明确地将你写的每个分配与一个平衡release呼叫配对。 对于你来说，当你把数组设为零时，你基本上泄漏了员工的所有内存。 您需要再次遍历数组以释放它们，或者更好，因为您正在学习… 尽快开始编写ARC代码。
可能很重要的一点是，ARC正是为这种情况而创build的; 这对我们的大脑是有意义的，现在如果你使用最新的工具，它可以成为现实。