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C# Intermediate C# Polymorphism Virtual Methods

Posted by Andrew Perry
Andrew Perry
5,266 Points

why does this code not compile?

I know what the solution is to this exercise, I need to delete the else statement and then have the method return false outside of the for loop. I don't understand why I can't return false with an else statement inside the for loop though.

SequenceDetector.cs 
namespace Treehouse.CodeChallenges
{
    class SequenceDetector
    {
        public virtual bool Scan(int[] sequence)
        {
            return true;
        }
    }

    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {
            for(int i = 1; i < sequence.Length; i++)
            {
                if(sequence[i] == sequence[i-1])
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }

        }
    }
}
RepeatDetector.cs

1 Answer

christopher vaughan
christopher vaughan
1,411 Points
christopher vaughan
christopher vaughan
1,411 Points

it doesn't compile because there's a possibility that the for loop will never run, in which case override lacks a return statement. for instance if sequence.Length == 0, i is never less than sequence.Length, so the for loop wouldn't trigger at all. 

int[] sequence; //sequence has no length

for(int i = 1; i < sequence.Length; i++){ //this will never execute

}
Andrew Perry
Andrew Perry
5,266 Points

makes sense, thanks for your help.