【iOS】Swift3 报错：Value of type ‘AppDelegate’ has no member ‘managedObjectContext’，UIApplication has no member ‘sharedApplication’

在Swift 3里面，需要通过viewContext访问managedObjectContext，且sharedApplication方法改为shared方法：

var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

1	var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

以前是这样写的：

var context = (UIApplication.sharedApplication.delegate as AppDelegate).managedObjectContext

1	var context = (UIApplication.sharedApplication.delegate as AppDelegate).managedObjectContext