If we check in the first if statement to see if obj is a Point object, why do we need to cast it into a Point?

Thanks for your responses! ISorry -- first time asking a question in the forum; didn't know that it wouldn't automatically link to the lesson page in question. Here's the code:

https://teamtreehouse.com/library/intermediate-c/systemobject/objectequals

Challenge Task 1 of 1

Add an Equals method to the VocabularyWord class that returns true if the words of two VocabularyWord objects are the same.

using System; namespace Treehouse.CodeChallenges { public class VocabularyWord { public string Word { get; private set; }

    public VocabularyWord(string word)
    {
        Word = word;
    }

    public override string ToString()
    {
        return Word;
    }

    public override bool Equals(object obj){
        if(!(obj is VocabularyWord))
        {
            return false;
        }
        VocabularyWord that = obj as VocabularyWord;

        return that.ToString() == this.ToString();
    }
}

}

I think I partly understand... but I guess what I don't understand is why an object that's already a Point (or in this case, a VocabularyWord) would not already have access to the members of its class. Doesn't it automatically get access to its Parent class' members if it's created as an instance of the Parent class?

Thanks for your patience -- this is my first real experience with OOP and I'm trying to make sure I really have a handle on the fundamentals before proceeding forward in the lessons.

It does automatically get access to the parent class. But what's happening here is since it was passed to the method as an object (not a VocabularyWord), it only has access the the parent (object) members until you cast it. It might be a VocabularyWord, but before casting the method code only sees it as an object and cannot use it to access members of VocabularyWord.

This is a significant OOP concept and I recognize your wish to understand it fully. I hope it makes more sense now.

Ohhhhh yes! Yeah, that makes sense now, and thanks for taking the time and effort to explain it to me.

Question -- if I'd passed in the var as a VocabularyWord object, would the method have access to all the parent class' methods, or would I have to cast it anyway? Is there any benefit to doing it that way or is it better to pass it to the method as an object and then cast?

Would something like this work?

public override bool Equals(VocabularyWord obj){ if(!(obj is VocabularyWord)) { return false; }

    return obj.ToString() == this.ToString();
}

Yes, that would work, but you could then eliminate the test for other types, since once you change the parameter any attempt to pass a different type would cause a compiler error.

And to your question, it has access to the parent class (object) members either way. It's only the VocabularyWord members that it doesn't have access to before casting when the parameter is declared as object. The difference between the argument types is that when the parameter is declared as an object, the method can be given any object as an argument and it will return a result. But if it is declared as a VocabularyWord, then it can only be passed objects of that type (or you get that compiler error I mentioned). In this case there's no choice to be made because this method is an override so the parameter type must match that of the original method.

Got it! Thanks so much!