basic Inheritance in XNA C#

Question

I'm trying to expand System.TimeSpan in C# because I need a extra method to convert the GameTime to a TimeSpan. This is what i tried:

class TimeSpanner : TimeSpan
{
}

apperently it's not possible to extend the Timespan struct. Does anyone know why it can't be extended? And how do I properly make this work?

score 2 · Accepted Answer · answered Jul 25 '11 at 00:21

You're taking completely the wrong approach. GameTime has member properties ElapsedGameTime and TotalGameTime that provide the two different TimeSpans that make up a GameTime object. Use them like this:

protected override void Update(GameTime gameTime)
{
    TimeSpan elapsed = gameTime.ElapsedGameTime;
    TimeSpan total = gameTime.TotalGameTime;

    // Personally, I just do this:
    float seconds = (float)gameTime.ElapsedGameTime.TotalSeconds;

    // ...
}

score 1 · Answer 2 · answered Jul 24 '11 at 20:14

You can not inherit from a struct.

Form MSDN on structs:

There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.

As an alternative to what you are trying, consider using extension methods.

score 1 · Answer 3 · answered Jul 24 '11 at 20:15

1

A TimeSpan is a struct and structs (which are a value type) cannot be subclassed. You should probably investigate using an operator to perform a conversion.

You could do something like this:

public static implicit operator TimeSpan(GameTime gt) 
{
    return gt.GetTimeSpan();
}

You could then use this like this:

TimeSpan timeSpan = (TimeSpan)myGameTime;

answered Jul 24 '11 at 20:15

CodingGorilla

19,612
4
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The conversion should be marked explicit rather than implicit if going down this route. – Jeff Mercado Jul 25 '11 at 00:27
1

And where would you put this conversion operator? `TimeSpan` and `GameTime` are both framework classes (.NET and XNA respectively). – Andrew Russell Jul 25 '11 at 00:30

score 1 · Answer 4 · answered Jul 24 '11 at 20:15

1

If you need an extra method to do a conversion then why not just make an extension method then?

public static void DoStuff(this TimeSpan timeSpan, GameTime gameTime)
{
     ...
}

answered Jul 24 '11 at 20:15

Scott

999
7
13

2

The extension method you've given isn't suitable for doing a conversion. – Andrew Russell Jul 25 '11 at 00:21

basic Inheritance in XNA C#

4 Answers4