Question

Class definition:

#import "MyClass.h"


@implementation MyClass

- (id)init
{
    self = [super init];
    if (self) {
        // Initialization code here.
    }

    return self;
}

- (void)dealloc
{
    [super dealloc];
}

- (void)print
{
    NSLog(@"Hello World");

}

@end

And main file:

MyClass * m = [[MyClass alloc]init];
[m print];

[m release];

[m print];

Result:

Hello World

Hello World

Why the 2nd method still invoked when object is released?

Answer 1

Releasing an object simply marks the memory it used as being available to be reused for other purposes. It doesn’t overwrite it with zeroes or anything like that. In your example, you haven’t created any new objects, so nothing has had a chance to reuse the memory formerly known as “m”.

This why it’s a common pattern to release an object and assign nil to the pointer, to prevent accidental re-use of an invalid object:

[m release]
m = nil;