CODEWITHSUNDEEP
c#listclass
William Jacobs
William Jacobs

Reputation: 9

Class specific method in list of different classes

so i Have a list consisting of different classes, all inheriting from a common class. Now i want to call for a method specific to one of those subclasses but i can't seem to find the right code to do that, could anyone help? the part of the code where it goes wrong (can't access the enemies list):

if (_floor.GetRoomByIndex(CheckActiveRoomIndex()).GetType() == typeof(StandardRoom))
{
    for (int i = 0; i < _floor.GetRoomByIndex(CheckActiveRoomIndex()).enemies.Count; i++)
    {
        _floor.GetRoomByIndex(CheckActiveRoomIndex()).enemies[i].UpdateBoundingBox();
    }
}

and here is part of my StandardRoom Class

class StandardRoom : CommonBaseClass
{
    public bool IsCleared { get; set; }
    public List<Enemy> ennemies = new List<Enemy>();
    ...
}

Upvotes: 0

Views: 67

Answers (2)

Emmanuel DURIN
Emmanuel DURIN

Reputation: 4913

William,

The problem is that _floor.GetRoomByIndex(CheckActiveRoomIndex()) is not a StandardRoom, but a Room (or the base class, whatever the name)

1/ Solution closer to existing code There is cast missing so that the rooms can be treated as StandardRoom : use the as keyword to cast in a safe way.

And Don't Repeat Yourself (DRY principle), declare a variable (stdRoom).

StandardRoom stdRoom = _floor.GetRoomByIndex(CheckActiveRoomIndex()) as StandardRoom;
if ( stdRoom != null )
{
  for (int i = 0; i < stdRoom.enemies.Count; i++)
  {
      stdRoom.enemies[i].UpdateBoundingBox();
  }
}

As says Olivier below, with C#7 pattern matching (Visual Studio 2017+), the cast can be shorter :

if ( _floor.GetRoomByIndex(CheckActiveRoomIndex()) is StandardRoom stdRoom )

2/ The Linq answer

Enumerable.SelectMany can be used to get Enemies from a Room

if ( _floor.GetRoomByIndex(CheckActiveRoomIndex()) is StandardRoom stdRoom )
{
  // projection to get Enemies from StandardRoom
  foreach( Enemy e in stdRoom.SelectMany( r => r.enemies ) )
  {
    e.UpdateBoundingBox()
  }        
}

Regards

Upvotes: 2

Karel Frajt&#225;k
Karel Frajt&#225;k

Reputation: 4489

LINQ has a tons of available methods. Read the documentation or just google 'LINQ methods'.

The method you are looking for is OfType<T> (see documentation page). This method will only select the items in the list of the required type T.

Upvotes: 1

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