C#•2mo ago

✅ Passing a potential NULL value, is it allowed?

namespace Calculator.Controller
{
    internal class CalculatorController
    {

        public static void Run(string[] input)
        {
            if (input == null)
            {
                InputHandler.zeroinputargument(input);
            }
            else
            {
                InputHandler.twoinputarguments(input);
            }
        }
    }
}

namespace Calculator.View
{
    public class InputHandler
    {
        // These two methods are used to determine if the array of input had 
        public static void zeroinputargument(string[] input)
        {
            
        }
        public static void twoinputarguments(string[] input) 
        { 
            
        }
    }
}

namespace Calculator.Controller
{
    internal class CalculatorController
    {

        public static void Run(string[] input)
        {
            if (input == null)
            {
                InputHandler.zeroinputargument(input);
            }
            else
            {
                InputHandler.twoinputarguments(input);
            }
        }
    }
}

namespace Calculator.View
{
    public class InputHandler
    {
        // These two methods are used to determine if the array of input had 
        public static void zeroinputargument(string[] input)
        {
            
        }
        public static void twoinputarguments(string[] input) 
        { 
            
        }
    }
}

Would this be valid even if the input argument for InputHandler.zeroinputargument(input); and InputHandler.twoinputarguments(input); might be NULL?

17 Replies

Merineth 🇸🇪•2mo ago

As in, what if my method runs argument was NULL. Would everything still work?

Jimmacle•2mo ago

the code as-is? sure, it doesn't automatically crash just because you passed null it will crash if you try to access members of a null variable, like accessing elements of the array or calling a method on the array

canton7•2mo ago

It rather depends on what zeroinputargument does with its input parameter

Merineth 🇸🇪•2mo ago

Ahhh zeroinputargument wont use input parameter might as well remove it :p :catlaugh: Not sure what i was thinking there, my bad Quick question

    internal class Calculator
    {
        static void Main(string[] args)
        {
            // Create an instance of the Class CalculatorController according to description of assignment.
            CalculatorController controller = new CalculatorController();
            // Call the method run() according to description of assignment.
            CalculatorController.Run(args);
        }
    }
}

    internal class Calculator
    {
        static void Main(string[] args)
        {
            // Create an instance of the Class CalculatorController according to description of assignment.
            CalculatorController controller = new CalculatorController();
            // Call the method run() according to description of assignment.
            CalculatorController.Run(args);
        }
    }
}

If this program was started where no arguemnts were specified would the string[] be NULL ?

Scarlet•2mo ago

No It would be an empty array

Merineth 🇸🇪•2mo ago

Aaah that makes sense So if I wanted to check for that I’d aim for something like if (args.Length == 0)

Scarlet•2mo ago

Actually if you pass no arguments then the array will have one item The item is the file path to the program

Merineth 🇸🇪•2mo ago

Interesting I’ll remake it and see You are a legend @a coding witch. It indeed comes out to 0!

Scarlet•2mo ago

Great There is another way to get the arguments

Merineth 🇸🇪•2mo ago

By any chance, do you also know if i were to do string text = Console.Readline(); And the user inputs 2 3 + would the 2 and 3 become also strings? Are there types that identify each one as is? For example 2 is int, 3 is int, space bar is string and + is string?

Jimmacle•2mo ago

ReadLine only gives you one string, and that string is everything the user typed before hitting enter you'll have to do some string processing/parsing to turn that one string into individual numbers/symbols/etc $tryparse will be relevant

MODiX•2mo ago

When you don't know if a string is actually a number when handling user input, use int.TryParse (or variants, e.g. double.TryParse)

if(int.TryParse("123", out int number))
{
    var total = number + 1;
    Console.WriteLine(total); // output: 124
}

if(int.TryParse("123", out int number))
{
    var total = number + 1;
    Console.WriteLine(total); // output: 124
}

TryParse returns a bool, where true indicates successful parsing. Remarks: - Avoid int.Parse if you do not know if the value parsed is definitely a number. - Avoid Convert.ToInt32 entirely, this is an older method and Parse should be preferred where you know the string can be parsed. Read more here

Merineth 🇸🇪•2mo ago

Interesting "Avoid int.Parse if you do not know if the value parsed is definitely a number." Isn't this unavoidable tho?

Jimmacle•2mo ago

no it's saying that if you aren't 100% sure the input string is a number, use TryParse instead for user input you won't ever know for sure, but for other applications like reading files another program generated you can make assumptions

Merineth 🇸🇪•2mo ago

ooh i see

Jimmacle•2mo ago

basically, you can use TryParse in an if instead of Parse in a try/catch and it's a bit nicer to look at and technically more efficient code

Merineth 🇸🇪•2mo ago

Hmm

namespace Calculator.Model
{
    public class CalculationHandler
    {
        public static void zeroinput(string text)
        {
            // We take the string of text and split it based on the ' ' space betwen each +,-,*,/, Int or Float.
            string[] parts = text.Split(' ');
            // Now we define foreach and every index of parts and determine it's type. 
            for (int i = 0; i < parts.Length; i++)
            {
                
            }
        }
    }
}

namespace Calculator.Model
{
    public class CalculationHandler
    {
        public static void zeroinput(string text)
        {
            // We take the string of text and split it based on the ' ' space betwen each +,-,*,/, Int or Float.
            string[] parts = text.Split(' ');
            // Now we define foreach and every index of parts and determine it's type. 
            for (int i = 0; i < parts.Length; i++)
            {
                
            }
        }
    }
}

I'm not too familiar with TryParse, woudl you be able advise me how it works? foreach might be more appropriate here but i've never used it before. Either way, i want to Parse every item inside the string[] parts now to it's appropriate type Ok nvm i decided on an if, else if statement to work around it thanks :catlove:

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✅ Passing a potential NULL value, is it allowed?