- @property (nonatomic, retain) NSNumber *count;
- (NSNumber *)count {
return _count;
}
- (void)setCount:(NSNumber *)count {
if (count != _count) {
id oldValue = _count; //在释放旧值之前保持他,防止其他线程通过_count访问到已释放的地址
_count = [count retain];
[oldValue release]; //安全释放旧对象
}
}
- @property (nonatomic, copy) NSNumber *count;
- (NSNumber *)count {
return _count;
}
- (void)setCount:(NSNumber *)count {
id oldValue = _count;
_count = [count copy];
[oldValue release];
}
//无需判断新旧count指针.OC runtime源代码也是这样做的.
- @property (atomic, retain) NSNumber *count;
- (NSNumber *)count {
NSNumber *count;
@synchronized(self) {
count = [_count retain];
}
return [count autorelease];
}
- (void)setCount:(NSNumber *)count {
id oldValue;
@synchronized(self) {
oldValue = _count;
_count = [count retain];
}
[oldValue release];
}
//http://www.cocoawithlove.com/2009/10/memory-and-thread-safe-custom-property.html
//retain + autorelease防止另一个线程中的setter在返回值之前释放该值
- @property (assign) int count;
- (int)count {
int count;
@synchronized(self) {
count = _count;
}
return count;
}
- (void)setCount:(int)count {
@synchronized(self) {
_count = count;
}
}
