[newbe] instantiating class variable in constructor

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Snaggy - 09 Jan 2008 21:06 GMT

Hi, this is my first day using c# and I must say it's cool but data
types.. I'm not use to them (php...) they're driving me crazy.

I need to declare a class variable, but I don't know it's type since
it's passed to the constructor when the object is created. I'd like
something like this:

class MyClass
{

public MyClass(int attribute)
{
if (attributes == 1)
{
string myDeck = "something";
}
else if (attributes > 1)
{
int myDeck = "123";
}
}

public string tellMe() // by the way I'm saying string, but
it might be integer... what the..
{
return myDeck;
}
}

how can I solve this mess? Can anyone reassure me that this compulsory
typing isn't actually just a headache?

bye!
Luca(IT)

Reply to this Message

Chris Shepherd - 09 Jan 2008 21:17 GMT

> Hi, this is my first day using c# and I must say it's cool but data
> types.. I'm not use to them (php...) they're driving me crazy.
>
> I need to declare a class variable, but I don't know it's type since
> it's passed to the constructor when the object is created. I'd like
> something like this:

[...]

> how can I solve this mess? Can anyone reassure me that this compulsory
> typing isn't actually just a headache?

Well, generally you would want to strongly type your data where possible. Is
there a practical reason you could not simply provide two separate properties to
provide access to your different data types?

Alternately, you could define your variable as "object", ie:
private object myDeck;

Chris.

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Snaggy - 09 Jan 2008 21:37 GMT

what do you mean 2 diff properties? I'd still have do declare my
variable after having constructed the object. Let me ask this, is it
possible to declare variable object wide (accessible through
this.varName) after having created the object? Or do I have to declare
them all and as object the typeToBeDefined ones?

(hope I explained myself..)

bye

Reply to this Message

sloan - 09 Jan 2008 21:42 GMT

if you don't know the type.. you can either use "object", (which is kinda
crappy)..or

Use a Generic. Here is a sample. (see below).

As far as "compulsary typing"...strong typing makes more maintainable code.
The time spent on code is maintenance, not development.

class MyClass<T>

{

private T _model = default (T);

public MyClass(T attribute)

{

_model = attribute;

}

public T FindIt()

{

return _model;

}

}

class Program

{

static void Main(string[] args)

{

MyClass<int> mc1 = new MyClass<int>(123);

int x = mc1.FindIt();

Console.WriteLine(Convert.ToString (x));

MyClass<Exception> mc2 = new MyClass<Exception>(new Exception("You can use
any object here with Generics!"));

Exception foundEx = mc2.FindIt();

Console.WriteLine( (foundEx.Message ));

MyClass<Guid> mc3 = new MyClass<Guid>(Guid.NewGuid());

Guid g = mc3.FindIt();

Console.WriteLine(g.ToString ("N"));

}

}

> Hi, this is my first day using c# and I must say it's cool but data
> types.. I'm not use to them (php...) they're driving me crazy.
[quoted text clipped - 30 lines]
> bye!
> Luca(IT)

Reply to this Message

Snaggy - 09 Jan 2008 22:36 GMT

I'll study a bit on that.. for today I decided to change approach.
Let's make everything a Dictionary!

can you look at this code (cards' deck, with method to add card and
its attributes which might be 1 or more)

class Deck
{
Dictionary<string, string[]> myDeck = new Dictionary<string,
string[]>();

public string getAttribute(string name)
    {
        return myDeck[name][0];
    }
public string getAttribute(string name, int attribute)
{
return myDeck[name][attribute];
}

    public void addCard(string name, string attribute)
    {
        if (attribute.Contains(",")){
String[] attributes = attribute.Split(',');
myDeck.add(name, attributes); <---- HERE
}
else
{
String[] attributes = { attribute };
myDeck.add(name, attributes);
}
    }

}

at the "HERE" I got this problem when tried to debug:

Error    1    'System.Collections.Generic.Dictionary<string,string[]>' does
not contain a definition for 'add' and no extension method 'add'
accepting a first argument of type
'System.Collections.Generic.Dictionary<string,string[]>' could be
found (are you missing a using directive or an assembly reference?)    C:
\Documents and Settings\Proprietario\Documenti\Visual Studio
2008\Projects\CardSke\CardSke\Program.cs    30    24    CardSke

what's that??
bye

Reply to this Message

Marc Gravell - 09 Jan 2008 23:26 GMT

> at the "HERE" I got this problem when tried to debug:

C# is case sensitive. Try Add(...)

Marc

Reply to this Message

Snaggy - 10 Jan 2008 13:14 GMT

> > at the "HERE" I got this problem when tried to debug:
>
> C# is case sensitive. Try Add(...)
>
> Marc

nope.. did it already

Reply to this Message

Jon Skeet [C# MVP] - 10 Jan 2008 13:21 GMT

<snip>

> nope.. did it already

If you've done it in both places already, it should compile. I took
your code, changed "add" to "Add" in both places, and added the
appropriate using directives, and it works fine.

Jon

Reply to this Message

Snaggy - 11 Jan 2008 16:30 GMT

> <snip>
>
[quoted text clipped - 5 lines]
>
> Jon

yeah, it seems so... it must have been some other problem too, thanks!

anyway.
Returning to the main topic.. is it possible to define a variable
that'll be class accessible in a method?

Reply to this Message

Jon Skeet [C# MVP] - 11 Jan 2008 16:31 GMT

<snip>

> Returning to the main topic.. is it possible to define a variable
> that'll be class accessible in a method?

No. You can only declare *local* variables in methods.

Jon

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[newbe] instantiating class variable in constructor

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