BrighterScript 'callfunc' operator

In BrightScript, calling a function on a custom comment requires you to use the callfunc function. A standard callfunc expression looks something like this: node.callFunc("functionName", someArg, someOtherArg). This deviates from the conventional object.someMethod() synax you are used to with standard objects.

Which leads us to the callfunc operator in BrighterScript. This is denoted by an at symbol followed by a period. ( @. ). Whenever BrighterScript encounters the callfunc operator, it will transpile the code into a valid callfunc expression, while allowing you to write mostly the same type of syntax you're used to for object method calls.

Here's a simple example:

node@.someMethod(1,2,3)

Gets transpiled to

node.callfunc("someMethod", 1, 2, 3)

Callfunc evaluation with no arguments

It is a well-known issue in BrightScript development that calling callfunc without at least one parameter has the potential to result in the function not being called at all. So to mitigate this issue, BrighterScript will automatically insert invalid as the first argument if you use the callfunc operator with no parameters.

For example, this:

node@.doSomething()

will be transpiled into this:

node.callfunc("doSomething", invalid)

It is the developer's responsiblity to ensure that the target function has at least one parameter, and that the type is dynamic, otherwise a type mismatch runtime error will occur.