Can I create new object inside loop?

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Can I Create New Object inside Loop?

Please assist me.

Below find sample code

Which one is good?

Option 1 or 2 or 3 .

Thank you !!!

What I have tried:

C#

class A
{
    public void MethodA()
    {

        //--------------
    }
}


class B
{
    A a = new A();
    public void MethodB()
    {
        for (int i = 0; i < 500000; i++)
        {
            a.MethodA();
        }
    }
}


class B
{
    A a;
    public void MethodB()
    {
        for (int i = 0; i < 500000; i++)
        {
            a = new A();
            a.MethodA();
        }
    }
}


class B
{
    
    public void MethodB()
    {
        for (int i = 0; i < 500000; i++)
        {
            A a = new A();
            a.MethodA();
        }
    }
}

Posted 27-Jun-18 21:32pm

Ramesh Balasubramani

Updated 27-Jun-18 21:40pm

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Comments

CHill60 28-Jun-18 3:37am

I was always taught to keep the declaration as close as possible to where it is first required so for me it should be Hide Copy Code
A a = new A();
inside the loop (the last option)... but be aware of variable scopeMy Bad - see solution 1

2 solutions

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Richard MacCutchan · Accepted Answer · 2018-06-27T21:38:00

Solution 1

The second and third options create 500,000 new objects of class A. Not a very good idea.

Posted 27-Jun-18 21:38pm

Richard MacCutchan

Comments

CHill60 28-Jun-18 3:39am

Ah - good point. I missed that

Richard MacCutchan 28-Jun-18 4:01am

But in a more complex (and useful) class, the second or third option could be the right way.

OriginalGriff · Accepted Answer · 2018-06-27T21:42:00

You can't compare them, they do different jobs, so there isn't a "best" or "good" one.
The first example

A a = new A();
public void MethodB()
{
    for (int i = 0; i < 500000; i++)
    {
        a.MethodA();
    }
}

Calls MethodA on teh same instance of the class every time.
The second example

A a;
public void MethodB()
{
    for (int i = 0; i < 500000; i++)
    {
        a = new A();
        a.MethodA();
    }
}

Creates a new instance for each time around the loop, and calls MethodA on that instance.

The difference is subtle, but if you think about cars then in the first instance you buy a car, and you drive it to work each day. In the second instance, you buy a new car each day and drive it to work, then discard it at the end of the day!

There is no "best" or "good" in that - for some approaches the first is right, for others it's the second.