Computing values before calling base constructor

Question

Is there any way in which you can call super constructor at the end of descendant class constructor?

It works in Java, but in C# the keyword base doesn't seem to be equivalent to Java's super.

Example:

class CommonChest : BasicKeyChest
{
    public CommonChest()
    {
        Random rnd = new Random();
        int key = rnd.Next(1, 6);
        int coins = rnd.Next(70, 121);
        super(key, coins, "Common");
    }
}

Answer 1

There is no way to postpone the call to the base constructor, it must complete before the derived constructor starts.

However, you can perform computations outside the derived constructor prior to calling the base constructor by providing an expression that you pass to the base:

class CommonChest : BasicKeyChest {
    public CommonChest()
    :   this(GenTuple()) {
    }
    private CommonChest(Tuple<int,int> keysCoins)
    :   base(keysCoins.Item1, keysCoins.Item2, "Common") {
    }
    private static Tuple<int,int> GenTuple() {
        Random rnd = new Random();
        int keys = rnd.Next(1, 6);
        int coins = rnd.Next(70, 121);
        return Tuple.Create(keys, coins);
    }
}

The above is a little tricky: a private constructor that takes a pair of ints is used to forward these ints to the base constructor. The tuple is generated inside GenTuple method, which is invoked before calling the base constructor.

Answer 2

NO, the concept of using base keyword or Constructor Initializer is that the base constructor gets called first and then child constructor. So that all common or shared parameters across the childs gets initialized first and then specific properties of child classes. That's also one of the reason why an abstract class can have Constructor

Answer 3

You could call a static method within the call to the base constructor:

class CommonChest : BasicKeyChest
{
    public CommonChest() : base(DoSomething())
    {

    }

    private static Tuple<int,int> DoSomething()
    {
        Random rnd = new Random();
        int key = rnd.Next(1, 6);
        int coins = rnd.Next(70, 121);
        return Tuple.Create(key, coins);
    }
}