Re: Passing globals and magic variables safely

[leriksen]

Some comments on the "action at a distance" effect.

I guess this is why I have become more and more a fan of truly functional programming, especially for the lack of side effects. I try very hard to avoid all "action at a distance" coding

Explicitly I try to write code

• consisting only of functions i.e. the main script is as small as possible, work is handed off to a function in a module as soon as possible. Typically my main script is limited to reading and checking constraints on command line options
• I try really hard to not have a function refer to anything outside of its immediate scope.
• I can only use a module's services via its functional interface i.e. I cannot do $Some::Module::variable = 'ugh'; from anywhere except inside Some::Module
• I try to limit functions to using only the parameters they are passed. When absolutely required, I will access a variable in the modules scope, but outside the modules function e.g. I try to avoid

  Package Some::Module;
  ...
  my $some_state = 'something';
  ...
  sub some_func {
     ...
     $some_state = 'new state';
     ...
  }
  

  
  as much as possible.
• For objects, I also try to apply these principles - except where really required, I prefer to use $self->some_accessor() than $self->{some_attribute}
• When I do have to break these rules and effect an "action at a distance" , it is really clear that I have to. The reason may be bad design or bad implementation, but at some point I have to say "until I can think of a better way, lets mark this as a TODO, and keep coding". Once the job at hand is working, I try to come back to the one or two instances of "action at a distance" and try to find a way to remove them

I have found this approach has made my code much better structured, much less complex, more flexible and more reusable.