CODEWITHSUNDEEP
c#generics
Admiral Land
Admiral Land

Reputation: 2492

How to return T type?

I have generic method:

private ILogger _logger; //get logger something else.
public T GetService<T>(ServiceType type)
{
 //how to return _logger?
}

How can i return T? For example, i have ILogger:

var logger=GetService<ILogger>(log);

How to implement GetService method? Thank you!

P.S. yes, i try to get one and more types from GetService method. For example: Logger, some other infrastructure classes. I know, that ServiceLocator is not right choise (is it uses in many places),but in my way (GetService will be use in one place: to get infrastructure for my plugins) i hope it is normal.

Upvotes: 5

Views: 29492

Answers (4)

Dieter Meemken
Dieter Meemken

Reputation: 1967

You have to declare T as new(), so it has to have a parameterless constructor. Then you can simply create an instance and return it:

    public T GetService<T>(ServiceType type) where T : new()
    {
        T t = new T();
        return t;
    }

Now, instead of new T() you could use others, may be your ServiceType..

Upvotes: -5

Enigmativity
Enigmativity

Reputation: 117037

It sounds like you are trying to create some sort of factory method based on type. Perhaps this might help:

public class Factory
{
    private ILogger _logger; //get logger something else.

    public Factory()
    {
        _factories = new Dictionary<Type, Func<Type, object>>()
        {
            { typeof(ILogger), t => _logger },
        };
    }

    private Dictionary<Type, Func<Type, object>> _factories;

    public T GetService<T>()
    {
        var t = typeof(T);
        return (T)_factories[t].Invoke(t);
    }
}

Upvotes: 6

newbie programmerz
newbie programmerz

Reputation: 419

try this:

private ILogger _logger; //get logger something else.
public T GetService<T>(ServiceType type)
{
// codes here...
return (T)(object) _logger;
}

Upvotes: 6

Patrick Hofman
Patrick Hofman

Reputation: 156948

I would start to make sure T implements ILogger. Then you have to cast the instance to T:

public T GetService<T>(ServiceType type) where T : ILogger
{
    return (T)_logger;
}

Note that this can cause invalid casts. To prevent exceptions on this and instead return null, you can use as:

public T GetService<T>(ServiceType type) where T : ILogger
{
    return _logger as T;
}

Upvotes: 1

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