CODEWITHSUNDEEP
c#
user3363744
user3363744

Reputation: 169

Passing Actions into generic functions

I'm trying to wrap my head around different concepts in Csharp by trying different things. A create a generic function that takes in an action. The action has one input parameter and returns void. I create a simple action that is linked to a lambda function (returns void has one parameter x). I am able to run the action but when I pass the function to my generic function I am not sure how to add the input parameter. act("Some Int") doesn't work.

How do I pass in a value to an action?

public MainWindow()
    {
        InitializeComponent();

        Action<int> myAction = (x) => Console.WriteLine(x);
        myAction(13);
        test(myAction);
    }

    private static void test<T>(Action<T> act)
    {
        act(); // How do i pass in an int Here?
    }

Upvotes: 0

Views: 72

Answers (2)

zimmerrol
zimmerrol

Reputation: 4951

Simply calling act("Some Int") as you have just required the Action act to be a genric function. Therefore you cannot specifically invoke it with one fixed variable type. You can solve your problem by modifying the test-method

 private static void test<T>(Action<T> act, T value)
 {
    act(value); // How do i pass in an int Here?
 }
 ...
 test(myAction,integerValue);

Now you can call the Action with a given intvalue.

Upvotes: 4

code4life
code4life

Reputation: 15794

I can see what you are trying to do, and just wanted to throw this pattern up, since we often do this when we have to use closures and the parameters could be wildly different.

In those cases, rather than define an Action<T> which kind of ties you down from being able to use closures, you would just simply define your method as Action. So test would look like this:

private static void test(Action act)
{
    act(); // yup, that's all there is to it!
}

So how would you pass in the parameter(s)? Simple: use closures. Like this:

public MainWindow()
{
    InitializeComponent();

    var x = 13; // this defined outside now...

    Action myAction = () => Console.WriteLine(x); // you're basically using the closure here.

    myAction();

    test(myAction);
}

We often use this sort of approach when we're context switching (aka thread jumping), and need the thread continuation to pick up one or more variable values at the point it executes. That's just one example, there's quite a few other valid use cases as well.

Your experimental example, if I'm reading it correctly, could also qualify as a situation where closures could be a good fit.

Upvotes: 1

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