Re: [octvae forge] shadowing between packages

[Andrew Janke]

On 3/16/19 8:28 PM, JuanPi wrote:
> Hi all,
>
> I need to ask suggestion on how to solve the following situation:
>
> 1. Package A implementes funcA
> 2. Package B also implementa funcA, but is much better than A's funcA
> 3. Package B depends on Package A
>
> Clearly Package A needs to run on itself, and if Package B is loaded
> funcA is now pointing to B's funcA... this means functions from A
> using funcA might fail (e.g. signature incompatibility)
>
> What solutions do you have?
>
> We have considered:
> 1. Renaming B's funcA to funcA_B ... not ideal, but well if that's it...
> 2. Creating a new package mirroring A, that renames funcA into funcA_A
> ... breaks all A's functions as does the shadowing, unless done
> everywhere
> 3. Renaming functions of package A when package B is loaded, and
> putting them back when package B is unloaded
>
> 2. is done via CVS, but as said is not actually a solution, unless one
> renames everythig
> 3. We do not know actually how to do it! :D
>
> Is 1. the only solution?
>
> Thanks

Namespaces. Or classes.

If Package A's funcA is for A's internal use, or has distinct semantics 
from Package B's funcA, it could go in a +pkgA namespace. And Package 
B's funcA could go in +pkgB. That way they can coexist, and each package 
calls its own funcA(). Instead of a namespace, you could also make them 
methods on distinctly-named classes in Package A and Package B.

If you want to replace them globally and dynamically, such that both 
packages will be calling the same funcA() implementation, but you can 
select which one at runtime, then you could use a "factory" pattern: 
Have a global func_a_provider class or function that returns a function 
handle to a funcA implementation. It uses one of them as a default. And 
it provides a "register" behavior that allows code to replace the 
default funcA implementation with another function (or class) at run 
time. Java and similar languages use "factory" and "service provider 
interface" patterns to do this.

Cheers,
Andrew