CODEWITHSUNDEEP
c#optional-parameters
Fabian
Fabian

Reputation: 2000

How can method overloading be avoided?

I have the following situation:

A constructor takes 6 values. Some of them have default values, some not.

#pseudocode# Foo(int a, int b=2, int c=3, int d=4, int e=5, int f){}

And I want to be able to call all possible combinations without having to write always all 6 parameters. 

#pseudocode# Foo f1 = new Foo(a=1, d=7, f=6);
#pseudocode# Foo f2 = new Foo(a=1, b=9, d=7, f=6);

Besides doing this with method overloading (which would be tedious), is there a more elegant solution?

Upvotes: 5

Views: 229

Answers (4)

moi_meme
moi_meme

Reputation: 9318

in C# 4, there are named parameters see Named and Optional Arguments (C# Programming Guide)

which would result in 

new Foo(a: 1, d: 7, f: 6);

Another solution wwould be to define a Constructor with your defaut value ans use Object Initializer to set the values How to: Initialize Objects by Using an Object Initializer (C# Programming Guide)

new Foo()
{
    a = 1,
    d = 7,
    f = 6
};

Upvotes: 12

James Michael Hare
James Michael Hare

Reputation: 38397

2 things:

1) default parameters are left to right, once you start defaulting parameters you cannot have a non-defaulted after it, so f must have a default (in your example)

2) you can use parameter naming to skip over a default parameter:

var f1 = new Foo(5, 9, e: 9, f: 10);

This gives a =5, b = 9, c = the default, d = default, e = default, f = 10

Provided you are using C# 4.0 compiler of course...

Upvotes: 0

Pete
Pete

Reputation: 11495

I would prefer refactoring to a Parameter Object. Something like:

Foo f1 = new Foo (new FooParameters () { B = 7 })

And your FooParamaters class can encapsulate the defaults:

public class FooParameters
{
     public int A { get; set; }
     public int B { get; set; }


     public FooParameters ()
     {
          A = 1;
          B = 2;
     }
}

Upvotes: 1

Martin
Martin

Reputation: 40325

use the following for naming arguments:

Foo f1 = new Foo(a: 1, d: 7, f: 6);
Foo f2 = new Foo(a: 1, b: 9, d: 7, f: 6);

More information on Named and Optional Arguments avalable here:

http://msdn.microsoft.com/en-us/library/dd264739.aspx#Y515

Upvotes: 1

Related Questions