Calling a constructor from another

[Sathyaish]

How does a constructor of one class call another of the same class?
When would this mechanism make sense or be required?


PS: Two instances I saw are:

(a) While using the Singleton pattern
(b) While using the Factory pattern

[Daniel O'Connell [C# MVP]]

Re: Calling a constructor from another


"Sathyaish" <Sathyaish@Yaho o.com> wrote in message
news:1116814208 .670220.215150@ z14g2000cwz.goo glegroups.com.. .[color=blue]
> How does a constructor of one class call another of the same class?[/color]

public MyClass() : this(<arguments >)
{
....
}

basically. You can also use base() to call a constructor on a base class[color=blue]
> When would this mechanism make sense or be required?[/color]

Generally, this allows you to specialize your constructors without redoing
code. Imagine you have a parameterless constructor that sets a few
properties to default values and one with a parameter that only sets one
property. By calling the parameterless constructor from your single
parameter one you bypass needing to re-write the code to set those
properties.

[Jon Skeet [C# MVP]]

Re: Calling a constructor from another

Sathyaish <Sathyaish@Yaho o.com> wrote:[color=blue]
> How does a constructor of one class call another of the same class?[/color]

See http://www.pobox.com/~skeet/csharp/constructors.html
[color=blue]
> When would this mechanism make sense or be required?
>
> PS: Two instances I saw are:
>
> (a) While using the Singleton pattern
> (b) While using the Factory pattern[/color]

I wouldn't expect either of these to use this pattern. I'd expect both
of them to have static methods/properties/initialisers which called the
constructor, but there's no need to have two constructors there.

It makes sense to have multiple constructors when there are several
parameters, some of which can take defaults. For instance:

public Foo() : this (0, 0)
{
}

public Foo (int x, int y)
{
this.x = x;
this.y = y;
}

allows defaulting of x and y to 0 by overloading. Usually in this kind
of situation all constructors end up calling the most specific one,
passing in default values.

--
Jon Skeet - <skeet@pobox.co m>

http://www.pobox.com/~skeet

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