如何将数组强制转换为NSMutableArray以便能够使用removeObjectAtIndex

Question

I have an array of users which I'm trying to cast as NSMutableArray to be able to use removeObjectAtIndex , but it doesn't work. I get either the error Cast from '[ModelUser]?' to unrelated type 'NSMutableArray' always fails Cast from '[ModelUser]?' to unrelated type 'NSMutableArray' always fails if I try to cast it, or '[ModelUser]' does not have a member named 'removeObjectAtIndex' if I don't.

So how could I remove an object from my array in this code?

query.friend(friendId, command: command, completion: { (result:Bool) -> () in
if result {
   self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
   if let friendR = self.friendRequests as? NSMutableArray{
        friendR.removeObjectAtIndex(indexPath.row)
   }
   println("Friendship deleted")
})

Answer 1

You can't turn an NSArray into an NSMutableArray simply by casting it - they are different classes. To get a mutable array from an NSArray you can invoke the mutableCopy method on the NSArray.

However, in your case the array is a Swift array, so it is already mutable.

You need to use removeAtIndex not removeObjectAtIndex to remove an object from a Swift array -

query.friend(friendId, command: command, completion: { (result:Bool) -> () in
if result {
   self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
   if self.friendRequests != nil {
        self.friendRequests!.removeAtIndex(indexPath.row)
   }
   println("Friendship deleted")
})

Answer 2

Actually you are doing a type casting only. You need to make friendR mutable to delete and add any object.

if let friendR = self.friendRequests.mutableCopy() as? NSMutableArray{
    friendR.removeObjectAtIndex(indexPath.row)
}

mutableCopy() and a new Instance of NSMutableArray would work.

Answer 3

you should use the following code to directly cast for example NSMutableArray to [YourType]

if var friendR = self.friendRequests as? AnyObject as? [ModelUser] {
    // your swift array handling code here
}

I used var keyword to enable future friendR mutations

Answer 4

您应该从一开始self.friendRequests初始化为NSMutableArray