Objective-c-ARC (Automatic Reference counting) automatic reference technical details

ARC characteristics and judgment criteria
/ *
 ARC's criterion: as long as there is no strong pointer to the object, the object will be released


 1.ARC Features
 1> Calling release, retain, retainCount is not allowed
 2> Dealloc can be overridden, but calling [super dealloc] is not allowed
 3> @ property's parameters
  * strong: member variable is a strong pointer (for OC object type)
  * weak: member variable is a weak pointer (for OC object type)
  * assign: applicable to non-OC object types
 4> The previous retain was changed to strong

 There are 2 types of pointers:
 1> Strong pointer: By default, all pointers are strong pointers __strong
 2> Weak pointer: __weak

 * /

int main ()
{
    Dog * d = [[Dog alloc] init];

    Person * p = [[Person alloc] init];
    p.dog = d;

    d = nil;

    NSLog (@ "% @", p.dog);

    return 0;
}

void test ()
{
    // Wrong writing (meaningless writing)
    __weak Person * p = [[Person alloc] init];


    NSLog (@ "% @", p);

    NSLog (@ "------------");
}
@class Dog;

@interface Person: NSObject

@property (nonatomic, strong) Dog * dog;


@property (nonatomic, strong) NSString * name;

@property (nonatomic, assign) int age;

@end
@implementation Person

-(void) dealloc
{
    NSLog (@ "Person is dealloc");

    // [super dealloc];
}

@end
@interface Dog: NSObject

@end
@implementation Dog
-(void) dealloc
{
    NSLog (@ "Dog is dealloc");
}
@end
ARC circular reference issue

/ **
 * When circularly referenced at both ends, the solution:
 1> ARC
 Use strong on one end and weak on the other

 2> Non-ARC
 Use retain on one end and assign on the other end
 * /
int main ()
{
    Person * p = [[Person alloc] init];


    Dog * d = [[Dog alloc] init];
    p.dog = d;
    d.person = p;

    return 0;
}
@class Dog;

@interface Person: NSObject

@property (nonatomic, strong) Dog * dog;

@end
@implementation Person

-(void) dealloc
{
    NSLog (@ "Person--dealloc");
}

@end
@class Person;

@interface Dog: NSObject

@property (nonatomic, weak) Person * person;

@end
@implementation Dog
-(void) dealloc
{
    NSLog (@ "Dog--dealloc");
}
@end
Objective-C-ARC (Automatic Reference Counting)