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C# C# Objects Object-Oriented Programming Initialization

Lee Wise
Lee Wise
1,335 Points
Posted by Lee Wise
Lee Wise
1,335 Points

I think this challenge is broken

Getting this error: Frog.cs(3,16): error CS1644: Feature `primary constructor' cannot be used because it is not part of the C# 6.0 language specification Compilation failed: 1 error(s), 0 warnings

Frog.cs 
namespace Treehouse.CodeChallenges
{
    class Frog ()
    {
        public readonly int TongueLength;

        Frog(int tongueLength)
        {
            TongueLength = tongueLength;
        }
    }
}

2 Answers

andren
andren
28,558 Points
andren
andren
28,558 Points

The challenge is fine, there are two errors in your code:

  1. You have parenthesis after "Class Frog" which should not be there, class declarations does not use parenthesis.

  2. You have not used an access modifier like public or private when declaring the constructor, which you need to do. Specifically for this case you need to make it public.

Fixing those two errors, like this:

namespace Treehouse.CodeChallenges
{
    class Frog
    {
        public readonly int TongueLength;

        public Frog(int tongueLength)
        {
            TongueLength = tongueLength;
        }
    }
}

Will allow you to complete the challenge.

Patrick McLeod
Patrick McLeod
5,913 Points
Patrick McLeod
Patrick McLeod
5,913 Points

Hi I was stuck on the same question and eventually gave up and found the answer here. Still don´t understand why I was supposed to state Frog as public though, If you could expand on the answer I would appreciate it. Cheers, PM

andren
andren
28,558 Points
andren
andren
28,558 Points

Sure Patrick McLeod I can expand on my answer.

If you don't include an access modifier (public, private, etc) when you declare something in a class then C# will set its access level to private by default. When the access level is private you can only access that thing within the class where it was declared.

The purpose of a constructor is to create an instance of the class, or put more simply to create an object. It is called automatically when you create an object. So this line of code for example:

Frog frog = new Frog();

Would end up calling the Frog constructor. However if a constructor is private then it can only be called within the class. Which means that you would be unable to create Frog objects anywhere besides inside of the Frog class itself.

One of the main points of classes is that you can create instances of them within other classes, so having a private constructor is extremely rare.

public things on the other hand can be accessed from any class in your program, and are therefore what most constructors are declared as.