C#•10mo ago

✅ How to do the C# equivalent of passing an std::function into a class

Hi, so I'm trying to make a class function that can accept a function of type float(float). I don't really understand how C# works because I'm coming from C++, which is very different than C# besides the names of data types. I've heard of delegates, but in all instances of a delegate parameter I've seen it as a pointer. Is a pointer bad C# syntax though in this case, since I'm trying to learn how to write C# well versus writing C# like C++. thanks in advance

12 Replies

Angius•10mo ago

Action or Func

public class Foo(Func<int, string> func)
{
    public void Print(int num)
    {
        Console.WriteLine(func(num));
    }
}

var f = new Foo(num => $"Number is {num}");
f.Print(69) // Number is 69

public class Foo(Func<int, string> func)
{
    public void Print(int num)
    {
        Console.WriteLine(func(num));
    }
}

var f = new Foo(num => $"Number is {num}");
f.Print(69) // Number is 69

UvuvwevweOnyetenyeOP•10mo ago

how is that not on the first page of bing 😭 thanks whats the point of delegate then at that point

Angius•10mo ago

With a delegate you can type those funcs and actions In the case above, you don't get any description of what that int is, for example But you can define

public delegate string SomeFunc(int numberOfLegs);

public delegate string SomeFunc(int numberOfLegs);

and use that

public class Foo(SomeFunc func)
{
    public void Print(int num)
    {
        Console.WriteLine(func(num));
    }
}

var f = new Foo(num => $"Number is {num}");
f.Print(69) // Number is 69

public class Foo(SomeFunc func)
{
    public void Print(int num)
    {
        Console.WriteLine(func(num));
    }
}

var f = new Foo(num => $"Number is {num}");
f.Print(69) // Number is 69

UvuvwevweOnyetenyeOP•10mo ago

so the Func could come out as an int with a string parameter instead? doesnt matter for my current setup cuz of my data types but

Angius•10mo ago

What do you mean? Yes, you can make the params and return type anything If that's what you're asking

UvuvwevweOnyetenyeOP•10mo ago

public class Foo(Func<int, string> func)
{
    public void Print(string arg)
    {
        int x = func(arg);
    }
}

public class Foo(Func<int, string> func)
{
    public void Print(string arg)
    {
        int x = func(arg);
    }
}

is that what you mean by not knowing what the int is?

Angius•10mo ago

No, you defined the func as something that takes an int and returns a string Not the other way around And what I mean is that the int has no name here It's just that, an int You don't know if it's age, weight, or number of eggs in a basket An explicit delegate declaration lets you name all the params as you see fit

UvuvwevweOnyetenyeOP•10mo ago

oh ok

Angius•10mo ago

Lets you even write doc comments for it So you get more help from the IDE

UvuvwevweOnyetenyeOP•10mo ago

dubs i get it now thanks

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✅ How to do the C# equivalent of passing an std::function into a class