CODEWITHSUNDEEP
c#classinstance
G. Enius
G. Enius

Reputation: 1

what does this mean? (about class and instance)

using System;

class Program
{
    static void Main()
    {
        haha haha1;
    }
}

class haha
{
    int a;
    int b;

    public haha(int a, int b)
    {
        this.a = a;
        this.b = b;
    }
}

I know if I want make instance, I should write code such as:

haha haha1 = new haha(1,2);

but when I write just

haha haha1;

there's no compile error.

What does haha haha1; mean? isn't it wrong code?

Upvotes: 0

Views: 49

Answers (2)

andlabs
andlabs

Reputation: 11598

That depends on the programming language, but most programming languages choose one of two options:

1) Implicit initialization (C++)

haha haha1;

is the same as

haha haha1 = new haha1();

2) Null initialization (C#)

haha haha1;

is the same as

haha haha1 = null;

Whatever happens, the result of the behavior is called the "default value" or "default initializer". Refer to your language documentation for details.

Some notes: C and C++ allows variables to be uninitialized, so they have no determinate value until you assign to them. C++ non-pointers cannot be NULL, so they are always initialized with something (but everything else, including pointers, follows the C rule).

Upvotes: 2

Vincent Ramdhanie
Vincent Ramdhanie

Reputation: 103145

It is not wrong code. It is a variable declaration.

haha haha1;

simply declares a variable named haha1 which has the type haha. However this variable was not assigned a value.

When you instantiate the object with the new keyword:

haha1 = new haha();

the variable then refers to the object created

Upvotes: 4

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