In GameMaker, the
is_undefined function is used to check if a variable has been defined or not. This is particularly useful when working with instances or data structures where you might not be sure if a certain value has been set.
Here's an example of how you can use
In the above code, if
playerScore wasn't previously declared and assigned a value, it would be considered undefined, and thus the condition would be true, leading to
playerScore being initialized to zero.
It's important to note that
undefined in GameMaker is a special constant representing a variable that has not been defined. It differs from simply having a variable with no value or a
null value as seen in some other programming languages.
You can also use
is_undefined when dealing with arrays or data structures:
With the introduction of GameMaker Studio 2.3.0, using
is_undefined became less common because of the improved variable scope and initialization. However, it remains a helpful function, especially in scenarios involving dynamic data or data received from external sources where uncertainty about variable definition might exist.