Question

So I have simple example of my code and I can’t find idea how to rewrite it.
Code:

 class Program
  {
    static void Main(string[] args)
    {
      var cat = new Cat();
      cat
        .ToFeed(arg => LikeMilk(1), c => c.Inc())
        .ToFeed(arg => LikeMilk(2), c => c.Inc());
    }

    private static bool LikeMilk(int liters)
    {
      return liters <1;
    }
  }

  public class Cat
  {
    private int Weith { get; set; }

    public void Inc()
    {
      Weith++;
    }

    public Cat ToFeed(Func<int, bool> predicate, Action<Cat> action)
    {
      if (predicate)  // Error: Cannot implicitly convert type 'System.Func<int,bool>' to 'bool' 
        action(this);
      return this;
    }
  }
}

Of course I can change signature ToFeed to ToFeed(bool predicate, Action<Cat> action), but I don’t want to do it.
I understand that I have to add int parameter to call of predicate, but I have added it in Main()

How can I solve this problem?

Thanks

Answer 1

You’re passing a function value to ‘ToFeed’ and not a bool value. That’s why you need to actually invoke the function:

if (predicate(this.liters))   //Check whether cat still wants milk. Yum!
    action(this);

Edit:
Now that I look closer at your code, I see that you hard coded the amount of liters in the main function and that thus the lambda-parameter arg is useless.

You should change the code in your main method to:

var cat = new Cat();
      cat
        .ToFeed(arg => LikeMilk(arg), c => c.Inc())
        .ToFeed(arg => LikeMilk(arg), c => c.Inc());

Now the lambda actually uses the parameter passed. Then you can add a liters-Variable to your Cat-class which you pass to the predicate. See my updated code above.