With this function you can check whether an instance scope variable exists or not. You supply the unique instance ID value (which can be found from the Instance Properties in the room editor, or is returned when you call the function instance_create_layer) as well as the variable name to check for as a string (see example code below). The function will return true if a variable with the given name exists for the instance and false otherwise.NOTE: This function is primarily for use with Compatibility Scripts for imported projects and the converted code for Drag and Drop actions.
Argument Description instance_id The unique ID value of the instance to check name The name of the variable to check for (as a string)
if !variable_instance_exists(id, "shields")) shields = 0;
The above code will check to see if the variable called "shields" exists in the instance running the code and if it does not then it is created and initialised to 0.