How to perform initializations of GAP objects in Julia packages?

[ThomasBreuer]

Consider the following file MyPackage.jl.

module MyPackage

using GAP

GAP.Globals.LoadPackage( GAP.julia_to_gap( "ctbllib" ) ) # or any other package

g = GAP.Globals.SymmetricGroup( 3 ) # pointer to a global variable that will be needed

function deal_with_g()
    return GAP.Globals.Size( g )
end

end # module

If one creates a proper Julia package from this (with dependency on GAP.jl listed in Project.toml) then the first using MyPackage will create a .ji file for MyPackage.
Leave Julia, start Julia anew, and call using MyPackage.
Now GAP is running, the Julia variable MyPackage.g exists, but the GAP object to which it shall point has not been created.
Analogously, GAP claims that the GAP package in question has not been loaded.
This is because the statements in MyPackage.jl are not executed w.r.t. the GAP that has been started now but w.r.t. the GAP that was used at compile time.

What is an elegant workaround for this situation?
I think it is quite common to have initializations of this kind.

[ThomasBreuer]

The answer is to use a __init__ function in the module,
see the documentation on Module initialization and precompilation.