How to set a default type for T in a static generic method?

Question

I am working with my own custom stacks class, and I am trying to create a generic method for creating a new stack(a generic object). I work a lot with stacks that are type int, and only occasionally need other types. Can I set the defult Type of T to int?

Here is the method:

public static Stack<T> newStack<T>(int length)
{
    Stack<T> s = new Stack<T>();
    for (int i = 0; i < length; i++)
    {
        Console.WriteLine("print num");
        string input = Console.ReadLine();
        T value = (T)Convert.ChangeType(input, typeof(T));
        s.Push(value);
    }
    return s;
}

I want to use the method like this:

newStack(5);//defult int type

and for any other type

newStack<string>(5)

Can anybody help? Thanks.

There's a few old questions that say that you can't, but I don't know if things have changed. The suggestion there is to make another method without the generic parameter that just calls the int verion. — Rup
– Rup, Commented Feb 10, 2020 at 10:15

Ivan Kahl · Accepted Answer · 2020-02-10 10:17:05Z

7

You can't specify a default type for T however you can simply overload the newStack method to get the behaviour you want. The overloaded method will automatically create a new stack of type int.

Your code would look something like this:

public static Stack<T> newStack<T>(int length)
{
    Stack<T> s = new Stack<T>();
    for (int i = 0; i < length; i++)
    {
        Console.WriteLine("print num");
        string input = Console.ReadLine();
        T value = (T)Convert.ChangeType(input, typeof(T));
        s.Push(value);
    }
    return s;
}

public static Stack<int> newStack(int length)
{
    // Call our original new stack method but pass
    // integer as the type T
    return newStack<int>(length);
}

Now you can call the second method if you just want to create a new stack of type integer like this:

newStack(5);

Otherwise you can create stacks of other types with:

newStack<string>(5);

answered Feb 10, 2020 at 10:17

Ivan Kahl

6183 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

INTODAN Over a year ago

Great answer. You answered first so I will accept your answer

GvS · Accepted Answer · 2020-02-10 10:17:07Z

1

Add a method newStack without the generics:

 public static Stack<int> newStack(int length) => newStack<int>(length);

The compiler is smart enough to select the correct method.

answered Feb 10, 2020 at 10:17

GvS

52.5k16 gold badges104 silver badges139 bronze badges

Comments

Corentin Pane · Accepted Answer · 2020-02-10 10:17:33Z

1

You could either bear with the generic formalism and use the int type when you need it:

Stack<int> myStack = newStack<int>(5);

but if you really want to, you can define another method without the type parameter that calls the generic version:

public static Stack<int> newStack(int length)
{
    return newStack<int>(length);
}

Stack<int> myStack = newStack(5);

answered Feb 10, 2020 at 10:17

Corentin Pane

4,9531 gold badge15 silver badges32 bronze badges

Comments

Johnathan Barclay · Accepted Answer · 2020-02-10 10:23:08Z

1

Short answer, you can't, but you could use a, non-generic overload:

public static Stack<int> newStack(int length)
{
    return newStack<int>(length);
}

edited Feb 10, 2020 at 10:23

answered Feb 10, 2020 at 10:17

Johnathan Barclay

20.5k2 gold badges27 silver badges40 bronze badges

Comments

Jongkwan Park · Accepted Answer · 2020-02-10 10:22:18Z

0

I think you can use overloading.

public static Stack<int> newStack(int length)
{
     return newStack<int>(length);
}

answered Feb 10, 2020 at 10:22

Jongkwan Park

886 bronze badges

Collectives™ on Stack Overflow

How to set a default type for T in a static generic method?

5 Answers 5

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related