objective-c 内存管理的文章摘录1

今天有空想学习一下objective-c的内存管理的知识就上网查了一些文章.

下面的这种方式是不对的
Instance you don’t own is sent release
- (void)reset {
NSNumber *zero = [NSNumber numberWithInteger:0];创建的是一个autorelease的对象
[self setCount:zero];
[zero release];//这里释放是危险的
}

When you add an object to a collection such as an array, dictionary, or set, the collection takes ownership of
it.在集合中增加object，那么这个object的所有者就变成了集合了
代码
// ...
for (i = 0; i < 10; i++) {
NSNumber *convenienceNumber = [NSNumber numberWithInteger:i];
[array addObject:convenienceNumber];
}
//这种情况不需要release

NSMutableArray *array;
NSUInteger i;
// ...
for (i = 0; i < 10; i++) {
NSNumber *allocedNumber = [[NSNumber alloc] initWithInteger: i];
[array addObject:allocedNumber];
[allocedNumber release];
}
//这种情况需要,此处只是将retain的计数减1而已
*******************************************
安全返回对象
下面两种方式是正确的
- (NSString *)fullName {
NSString *string = [NSString stringWithFormat:@"%@ %@", firstName, lastName];
return string;
}

- (NSString *)fullName {
NSString *string = [[[NSString alloc] initWithFormat:@"%@ %@", firstName,
lastName] autorelease];
return string;
}

相反，下面的方式是错误的
(NSString *)fullName {
NSString *string = [[[NSString alloc] initWithFormat:@"%@ %@", firstName,
lastName] release];
return string;
}

同样，下面的方式也是错的
(NSString *)fullName {
NSString *string = [[NSString alloc] initWithFormat:@"%@ %@", firstName,
lastName];
return string;
}