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Using Arguments

This documentation explains how to pass arguments to a script when executing it from C++.

Defining the Argument Callback​

To pass arguments to a script, define a callback function that populates an IValues container with the values you want to pass.

Example​


// This is what the macro looks like //
#define VARJUS_DEFINE_ARGS(Name, ctx, args)\
void Name(struct CProgramRuntime* const ctx, IValues& receiver)
///////////////////////////////////////

VARJUS_DEFINE_ARGS(AddArgs, ctx, receiver)
{
    receiver.push_back(CIntValue::Construct(ctx, 420));
    receiver.push_back(CStringValue::Construct(ctx, "Hello!"));

    receiver.push_back(CArrayValue::Construct(ctx, {
        CIntValue::Construct(ctx, 1),
        CStringValue::Construct(ctx, "Array hello!")
    }));
}

Notes​

  • Use Construct methods to create values instead of manual allocation.
  • You can pass multiple values, including arrays and complex data structures.
  • The receiver list will contain the arguments that the script will receive in the main(args) function.

Passing Arguments to a Script​

Once the callback is defined, pass it to ExecuteScript when executing the script.

Example​

#include "varjus_api/varjus_api.hpp"

int main()
{
    // Create a new execution state
    Varjus::State state;

    // Load libraries and the script...

    // Execute the script with arguments
    if (const auto returnValue = state.ExecuteScript(AddArgs)) {
        fmt::print(std::cout, VSL("The program returned: {}\n"), returnValue->ToPrintableString());
    }
}

Explanation​

  • ExecuteScript(AddArgs) ensures that AddArgs is invoked before execution, providing arguments to the script.
  • The script receives the arguments in the args parameter of main(args).

Accessing Arguments in a Script​

When a script is executed with arguments, they can be accessed in the main(args) function.

Example​

fn main(args)
{
    for (const arg : args)
        console.log(arg); // Output: 420, "Hello!", [1, "Array hello!"]
}

Notes​

  • The args parameter will contain the values passed from C++.
  • Each value retains its original type.
  • If no arguments are passed, avoid declaring args in main() to prevent errors.

Additional Considerations​

  • Flexibility: Use this mechanism to dynamically configure script behavior based on C++ input.