Loading application variables

Pupeno <>
Sun Jun 11 16:42:55 CEST 2006


On Sun, 2006-06-11 at 16:25 +0200, Ulf Wiger wrote:
> Den 2006-06-11 14:42:43 skrev Pupeno <>:
> 
> > I understand it can be written, but since nobody has written it yet I
> > suppose people work in other ways, if so, I want to learn that instead
> > of writing a function (that doesn't belong to my project anyway, but to
> > Erlang itself).
> 
> What I normally do is (possibly) use environment variables to store
> defaults, and then providing an API for setting the desired values
> at runtime.
> 
> Mnesia, for example, relies on environment variables for various settings,  
> but you can also call mnesia:start(Options), and set the same values that  
> way. What mnesia does at startup is to read the options - either passed as  
> arguments to the start function, or given as environment variables - and  
> then storing them as temporary objects in the schema.
> 
> The module proplists is a convenient way to handle {Key, Value} options.  
> You can, for example, do:
> 
> start(StartOpts) ->
>    Options = StartOpts ++ application:get_all_env(?APP_NAME),
>    Port = proplists:get_value(port, Options),
>    ...
> 
> 
> The proplists module will fetch the first instance of a given key, so all  
> you need to do to override the defaults is to prepend the new values to  
> the list.

Does this mean that I would not be using the standard way of application
to load configuration files ?
-- 
Pupeno <> http://pupeno.com
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