uiview - 调用 UIViews 的 subviews 属性将 subview retain count 增加 1？

Question

我有这个代码：

UIView *superView = [[UIView alloc] init];
UIView *subView = [[UIView alloc] init];
[superView addSubview:subView];
[subView release];
NSLog(@"retain before %i", [subView retainCount]);//prints 1
int i = superView.subviews.count ;
NSLog(@"retain after %i", [subView retainCount]);//prints 2
i = superView.subviews.count ;
NSLog(@"retain odd %i", [subView retainCount]);//keeps printing 2

这是“预期”的行为吗？如果是这样，基本逻辑是什么？