将对象设置为nil时,不会调用objective-c – dealloc方法

> person = nil不会在非ARC代码中释放对象.它将在ARC代码中(至少如果它很强大).
>在ARC中,当本地对象超出范围时,将自动为您释放它们.在非ARC中,不会为您释放超出范围的对象(如果您在其他地方没有其他对这些对象的引用,则最终会泄漏).
>将项添加到可变数组将增加项的保留计数,因此即使您在非ARC代码中包含一个版本,该对象也不会被释放,直到保留计数降至零(不仅仅由将person对象添加到数组后释放person对象,但也从数组中删除它们.

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
}