C#•6mo ago

Variable scoping

Considering this code:

BackgroundWorker backgroundWorker = new();


client.Initialize();
await client.Authenticate();
client.AddCallback<TestObject>(ShowOrders);

var testString = "a";
XX test = new()
{
    Test = "xx"
};

void ShowOrders(TestObject response)
{
    test.Test = "xx";
    testString = "b";
}

for (var x = 0; x<9; x++)
{
    await client.GetAccount();
    await Task.Delay(500);
}

backgroundWorker.RunWorkerAsync(client.Receive());
await Task.Delay(5000);

System.Console.WriteLine(testString);

public class XX {

    public string? Test { get; set; }

}

BackgroundWorker backgroundWorker = new();


client.Initialize();
await client.Authenticate();
client.AddCallback<TestObject>(ShowOrders);

var testString = "a";
XX test = new()
{
    Test = "xx"
};

void ShowOrders(TestObject response)
{
    test.Test = "xx";
    testString = "b";
}

for (var x = 0; x<9; x++)
{
    await client.GetAccount();
    await Task.Delay(500);
}

backgroundWorker.RunWorkerAsync(client.Receive());
await Task.Delay(5000);

System.Console.WriteLine(testString);

public class XX {

    public string? Test { get; set; }

}

Trying to compile, within the "ShowOrders" function, the client.AddCallback<TestObject>(ShowOrders); line gives the error : Use of unassigned local variable 'test' Why does it not complain about testString ?

16 Replies

Angius•6mo ago

$scopes

MODiX•6mo ago

scope A {
  thing a;
  scope B {
    thing b;
  }
}

scope A {
  thing a;
  scope B {
    thing b;
  }
}

thing a is available in scope A and scope B thing b is available only in scope B

Angius•6mo ago

Also, you have to understand top-level code, and that what it actually does, is puts your code into a class and a method So your

var foo = 69;

void Bar()
{
    Console.WriteLine($"{foo} is nice");
}

var foo = 69;

void Bar()
{
    Console.WriteLine($"{foo} is nice");
}

really becomes something akin to

internal class Program
{
    private static void Main(string[] args)
    {
        int foo = 69;
    }

    private static void Bar()
    {
        Console.WriteLine($"{foo} is nice");
    }
}

internal class Program
{
    private static void Main(string[] args)
    {
        int foo = 69;
    }

    private static void Bar()
    {
        Console.WriteLine($"{foo} is nice");
    }
}

Or, well, wait In your case it's actually a local function

Moods•6mo ago

yeah you shot yourself in the foot by going the top-level statement approach

Pannekoekje•6mo ago

I'm just trying out some lib with a simple program 🙂

Moods•6mo ago

yeah i think the middle function becomes a local one but i wouldnt be sure i avoid tls

Angius•6mo ago

You can use TLS, you just need to understand what it does Generally speaking, move your functions to the end of the file

Pannekoekje•6mo ago

The client is the lib, therefor the test.Test would be accessed via there?

Angius•6mo ago

After the top-level code

Pannekoekje•6mo ago

Ok, so considering this

namespace Application
{
    class Test
    {
        static async Task Main()
        {
            var client = Client.Create
                                      .WithApiKey("xx")
                                      .WithApiSecret("xx");

            BackgroundWorker backgroundWorker = new();


            client.Initialize();
            await client.Authenticate();
            client.AddCallback<PrivateGetAccountResponse>(ShowOrders);

            var testString = "a";
            XX test = new()
            {
                Test = "xx"
            };

            void ShowOrders(PrivateGetAccountResponse response)
            {
                test.Test = "xx";
                testString = "b";
            }

            for (var x = 0; x < 9; x++)
            {
                await client.GetAccount();
                await Task.Delay(500);
            }

            backgroundWorker.RunWorkerAsync(client.Receive());
            await Task.Delay(5000);

            System.Console.WriteLine(testString);
        }

        public class XX
        {
            public string? Test { get; set; }
        }
    }
}

namespace Application
{
    class Test
    {
        static async Task Main()
        {
            var client = Client.Create
                                      .WithApiKey("xx")
                                      .WithApiSecret("xx");

            BackgroundWorker backgroundWorker = new();


            client.Initialize();
            await client.Authenticate();
            client.AddCallback<PrivateGetAccountResponse>(ShowOrders);

            var testString = "a";
            XX test = new()
            {
                Test = "xx"
            };

            void ShowOrders(PrivateGetAccountResponse response)
            {
                test.Test = "xx";
                testString = "b";
            }

            for (var x = 0; x < 9; x++)
            {
                await client.GetAccount();
                await Task.Delay(500);
            }

            backgroundWorker.RunWorkerAsync(client.Receive());
            await Task.Delay(5000);

            System.Console.WriteLine(testString);
        }

        public class XX
        {
            public string? Test { get; set; }
        }
    }
}

Angius•6mo ago

Also, I wonder about that .AddCallback(), smells of a callback-hell-ish thing from pre-async times I'd need to know what the lib is to tell for sure, tho

Pannekoekje•6mo ago

Its something I wrote a while ago, with the callback added to an object to invoke them later on

Angius•6mo ago

Well, in any case, you're passing a local function as a delegate So chances are it's non-capturing

Pannekoekje•6mo ago

Alright, I think that's it. thx 🙂

jcotton42•6mo ago

You should not be using BackgroundWorker

jcotton42•6mo ago

https://blog.stephencleary.com/2013/05/taskrun-vs-backgroundworker-intro.html

Task.Run vs BackgroundWorker: Intro

This is an introductory post for a new series that I’ll be doing comparing BackgroundWorker to Task.Run (in an async style). I always recommend Task.Run, and I have already written a long post describing why, but I still see some developers resisting the New Way of Doing Things (TM). So this will be a short series where I’ll compare the code sid...

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