当我做下面的事情时,我得到一个错误说
for (UIView* att in bottomAttachments) { if (i <= [cells count]) { att = [[UIView alloc] extraStuff] } }
__strong做了什么以及为什么要添加它?
解决方法
If a variable is declared in the condition of an Objective-C fast enumeration loop,and the variable has no explicit ownership qualifier,then it is qualified with
const __strong
and objects encountered during the enumeration are not actually retained.Rationale
This is an optimization made possible because fast enumeration loops promise to keep the objects retained during enumeration,and the collection itself cannot be synchronously modified. It can be overridden by explicitly qualifying the variable with__strong
,which will make the variable mutable again and cause the loop to retain the objects it encounters.
正如Martin在评论中指出的那样,值得注意的是,即使使用__strong变量,通过重新分配它你也不会修改数组本身,但是你只需要将局部变量指向另一个对象.