Question

Possible Duplicate:
Initialize class fields in constructor or at declaration?

We are arguing about coding practices. The examples here are a little too simple, but the real deal has several constructors. In order to initialise the simple values (eg dates to their min value) I have moved the code out of the constructors and into the field definitions.

public class ConstructorExample
{
    string _string = "John";
}

public class ConstructorExample2
{
    string _string;

    public ConstructorExample2()
    {
        _string = "John";
    }
}

How should it be done by the book? I tend to be very case by case and so am maybe a little lax about this kind of thing. However i feel that occams razor tells me to move the initialisation out of multiple constructors. Of course, I could always move this shared initialisation into a private method.

The question is essentially … is initialising fields where they are defined as opposed to the constructor bad in any way?

The argument I am facing is one of error handling, but i do not feel it is relevant as there are no possible exceptions that won’t be picked up at compile time.

Answer 1

It’s not necessarily bad to initialize values outside of the constructor, and the problem you have here:

 string _string;

    public ConstructorExample2()
    {
        _string = "John";
    }

Is that if you have multiple constructors you have to remember to either
1. Reinitialize _string in every constructor
2. Separate the logic out into a common method and call that method in every constructor
3. Call the constructor with the logic in it, from the other constructors. (Chain the constructors)
Now this isn’t necessarily a problem, but you have to remember to do it. By initializing it outside of the constructor, it’s done for you. It’s one less thing you need to remember to do.