在項目開發(fā)中使用 popVC?.modalPresentationStyle = UIModalPresentationStyle.popover 做彈窗的時候出現(xiàn)了崩潰，報錯

Terminating app due to uncaught exception 'NSGenericException', reason: 'UIPopoverPresentationController 
(<UIPopoverPresentationController: 0x1042a5cc0>) should have a non-nil sourceView or barButtonItem set before the 
presentation occurs.'

我的代碼

        let  popVC = TestPopViewController()
        popVC.popoverPresentationController?.barButtonItem = UIBarButtonItem(customView: customView)
        popVC.popoverPresentationController?.backgroundColor = UIColor(hexNumber: 0x000000, alpha: 0.5)
        popVC?.modalPresentationStyle = UIModalPresentationStyle.popover
        popVC?.popoverPresentationController?.delegate = self
        present(popVC, animated: true, completion: nil)

最后發(fā)現(xiàn)在使用Controller 的屬性modalPresentationStyle 設(shè)置其樣式以及給Controller設(shè)置其他屬性的時候一定要先設(shè)置好modalPresentationStyle，然后再設(shè)置其他屬性
正確的使用方法

        let  popVC = TestPopViewController()
        popVC?.modalPresentationStyle = UIModalPresentationStyle.popover
        popVC.popoverPresentationController?.barButtonItem = UIBarButtonItem(customView: customView)
        popVC.popoverPresentationController?.backgroundColor = UIColor(hexNumber: 0x000000, alpha: 0.5)
        popVC?.popoverPresentationController?.delegate = self
        present(popVC, animated: true, completion: nil)