Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

C# Intermediate C# Abstraction Abstract Classes

Xiaolong Yang
Xiaolong Yang
4,374 Points
Posted by Xiaolong Yang
Xiaolong Yang
4,374 Points

Base class is less accessible than subclass

I tried to change "public class SequenceDetecter" to "abstract class SequenceDetecter", but it tells me that "base class Treehouse.CodeChallenges.SequenceDetector' is less accessible than classTreehouse.CodeChallenges.ReapeatDetecter' ". It could pass only if I write "public abstract class SequenceDetecter", why? In the video, public was not included...

SequenceDetector.cs 
namespace Treehouse.CodeChallenges
{
    abstract class SequenceDetector
    {
        public virtual string Description => "";

        public int[] LastScannedSequence { get; protected set; }

        public virtual bool Scan(int[] sequence)
        {
            LastScannedSequence = sequence;
            return true;
        }
    }
}
RepeatDetector.cs 
namespace Treehouse.CodeChallenges
{
    public class RepeatDetector : SequenceDetector
    {
        public override string Description => "Detects repetitions";

        public override bool Scan(int[] sequence)
        {
            LastScannedSequence = sequence;

            if(sequence.Length < 2)
            {
                return false;
            }

            for(int i = 1; i < sequence.Length; ++i)
            {
                if(sequence[i] == sequence[i-1])
                {
                    return true;
                }
            }

            return false;
        }
    }
}

1 Answer

Steven Parker
Steven Parker
231,268 Points
Steven Parker
Steven Parker
231,268 Points

:point_right: The access level of the class in the video was different.

In the video, class Invader was not public to begin with, so that aspect of it did not change.

But in this challenge, SequenceDetector was already public. And, as you discovered, it must remain that way because it is used as a base for RepeatDetector, which is also public.

Xiaolong Yang
Xiaolong Yang
4,374 Points
Xiaolong Yang
Xiaolong Yang
4,374 Points

Sorry for replying so late, thanks for your help ~~