MValues

This article will explain what MValues are and how to use them in your module.

What are MValues

MValues are containers that store a value of some specific data type. They are created so that a value can be exchanged between different programming languages without much hassle.

There is an MValue Type for every different data type one would need to exchange between resource and/or client and server. For example there is an MValue for Integers, the MValue stores the C++ integer and then the MValue can be passed to e.g. an event. The module then has to convert the C++ value stored in the MValue to the corresponding value in the programming language the module offers.

The different MValue types

In total there are 13 different MValue types, each of these types is used to store some other type of data.

Here is a list of all different MValue types:

Type	Description
None	An implicit empty value, used for invalid values
Nil	An explicit empty value, used for null in most languages
Bool	A boolean value (true/false)
Int	A whole number, can be either positive or negative
UInt	A whole number, can only be positive
Double	A floating point number
String	A text value
List	A collection of multiple elements (aka. array)
Dict	A dictionary with key-value pairs
BaseObject	An alt:V base object (Objects like vehicles, players etc.)
Function	A function that can be called
Vector2	A two-dimensional vector
Vector3	A three-dimensional vector
RGBA	A R(ed), G(reen), B(lue), A(lpha) color
ByteArray	An array of raw bytes

To verify all MValue types available see the SDK source code.

All MValue number types are 64-bit and floating-point numbers are doubles

How to create MValues

The module can create MValues by using the methods provided by alt::ICore. There is at least one method for every different MValue type, which returns that MValue type.

A small example on how to create an MValue and get the data stored in it can be found here:

// Create the MValue by using the method from the core
alt::MValueInt mvalue = alt::ICore::Instance().CreateMValueInt(4324);

// Get the data stored in the MValue
// All MValue types have a 'Value' method that returns it's stored method
int64_t value = mvalue.Value();

// You can also check the type of the MValue if its a generic MValue
alt::IMValue::Type type = mvalue.GetType();
if(type == alt::IMValue::Type::INT)
{
    // Now the MValue can be casted to the correct MValue class
    auto castedMvalue = static_cast<alt::MValueInt>(mvalue);
}

Another example can be found in the article about event handling.

All the methods to create MValues can be found here.