CODEWITHSUNDEEP
c#delegates
Jimmyt1988
Jimmyt1988

Reputation: 21126

Calling my function I passed through as a parameter

I have a function:

public void Callback()
{
    // Does some stuff
}

I want to pass that in to another function, which then passes it to another function, which then executes the function... I have this so far:

public void StartApp() // entry point
{
    StartMyAwesomeAsyncPostRequest( Callback );
}

public void StartMyAwesomeAsyncPostRequest( Delegate callback )
{
    // Work out some stuff and start a post request
    TheActualAsyncPostRequest( callback );
}

public void TheActualAsyncPostRequest( Delegate callback )
{
    // Do some jazz then run the delegated function
    callback();
}

I have looked through a few other examples but coming from a PHP and javascript background, I'm struggling with the explanations, can you perhaps give me an example or explanation specific to my request? Thanks in advance!

Upvotes: 2

Views: 82

Answers (1)

p.s.w.g
p.s.w.g

Reputation: 148980

Try declaring the parameter type as a particular kind of delegate. In this case, since your callback doesn't accept any argument and doesn't return any results, use an Action:

public void StartMyAwesomeAsyncPostRequest(Action callback)
{
    TheActualAsyncPostRequest(callback);
}

public void TheActualAsyncPostRequest(Action callback)
{
    callback();
}

If you wanted to be able to pass an argument to the callback, use an Action<T> (or one of its many cousins, to pass more than one argument):

public void StartMyAwesomeAsyncPostRequest(Action<string> callback)
{
    TheActualAsyncPostRequest(callback);
}

public void TheActualAsyncPostRequest(Action<string> callback)
{
    callback("Foo");
}

Or to get a result from the callback, use a Func<T> (or one of its many cousins, to pass in any arguments):

public void StartMyAwesomeAsyncPostRequest(Func<string> callback)
{
    TheActualAsyncPostRequest(callback);
}

public void TheActualAsyncPostRequest(Func<string> callback)
{
    string result = callback();
}

Upvotes: 7

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