为ui元素分配弱引用时，为什么我的应用程序崩溃？

Question

My app crashes when assigning ui elements weak reference in code, though by default when using storyboards ui elements are forced to be assigned weak reference.

class UploadContactShowViewController: BasePage,UITableViewDelegate,UITableViewDataSource, DARChatPhoneShowCellDelegate {

    var counter = 0

    var delegate: UploadContactShowViewControllerDelegate?
    var contact: APContact?

    var contactSelected: APContact?
    var contacts: [DARContact] = []
    var selectedContacts: [DARContact]!
    var checkBoxs: [BEMCheckBox]!

    var avatarImageView: UIImageView!
    var fullNameLabel: UILabel!
    var tableView: UITableView!
}

Answer 1

When a Storyboard (or a xib) unarchives the UI elements it adds them as subviews to the existing view. Because of this there is a strong reference (subviews are strongly referenced) and although IBOutlets are weak, there is a strong reference to prevent them from being deallocated.

If you are creating views in code and adding them to weak references, unless you have already added them as a subview, there is no reference so nothing is holding onto these UI Items, so they are deallocated.