excel vba - vba project reference and shared state (for logging) -

say have 2 add-ins a , b - both use vb functions shared add-in c (i.e. a , b have reference vb project c).

c log messages file (e.g. c.log) when errors detected. want c logs a.log when functions called , b.log when functions called b.

the naive approach set global variable in c log-file name not work, because variable singleton, last project set variable (a, or b) win.

how can done in vba?

okay - here's solution came (quite code, seems work fine):

i have logging project logging interface ilog (instancing publicnotcreatable) this:

public sub error(slogmessage string) end sub public sub warning(slogmessage string) end sub ' etc. 

and of course implementing class clog writes messages log-file.
, public function callers can new instance of logger:

public function new_log(byval logfilepathandname) ilog     set new_clog = new clog     new_clog.initialise logfilepathandname end function 

then project c must have it's code in class/or classes ilog instance in initialisation. example csharedclass so:

private log ilog ' note: var intentionally not called molog  public sub initialise(ologger ilog)     set log = ologger end sub  ' other functions in class want log use this: public sub someprocedure()     log.error("error text") end sub 

also project must have 1 public function let callers create instance, this:

public sub new_sharedclass(ologger ilog) csharedclass ' note: may want use interface instead     set new_sharedclass = new csharedclass     new_sharedclass.initialise ologger end sub 

then projects , b use logging this:

private molog ilog  public function log() ilog     ' log-file name of course different proejct b     if molog nothing set molog = new_log("projecta.log")     set log = molog end function 

all other procedures in project a/b can write log-messages (same in shared project)

log.error("error text") 

when project a/b wants use shared project, can so

private mosharedclass csharedclass   public function sharedclass() csharedclass         if mosharedclass nothing set mosharedclass = new_sharedclass(log)     set sharedclass = mosharedclass end function 

now code in project a/b wants call proc on shared class can this:

sharedclass.someprocedure() 

and log messages written in someprocedure end in correct log-file

note: decided break of own naming rules, projects can use same code logging (which has benefit can move procedures projects a/b shared project or vice versa)