Question

I define

@property (nonatomic, assign) int currentUserNum;
@property (nonatomic, assign) BOOL isAlive;

in @interface MyClass

and defined -init method in @implementation MyClass

@synthesize currentUserNum, isAlive;
-(id) init {
  if (self = [super init])  {
     self.currentUserNum = 0;
     self.isAlive = YES;
  }
  return self;
}

self.currentUserNum = 0; is crashed , but self.isAlive = YES; can work ! They are both assign property.

I want to know why ? Thanks!

Answer 1

Your init method is missing a lot of important code.

- (id)init {
    if ((self = [super init])) {
        _currentUserNum = 0; // it's not wise to reference properties in the init method
    }

    return self;
}

Every init method should follow this basic pattern. You assign self the value of calling an appropriate super init or other self init. If that’s not nil, you then perform appropriate initialization code, and finally you return self.