From: Chuck Remes <cremes.devlist@...>
Date: 2009-05-17T05:31:02+09:00
Subject: Re: BitStruct technique


On May 14, 2009, at 4:53 PM, Joel VanderWerf wrote:

> Chuck Remes wrote:
>>

>> In this example I passed in a hash as my message, but the +message+  
>> variable could have been any object that could be interrogated to  
>> retrieve values for setting the bitstruct fields. I like this  
>> technique because it delegates the responsibility of proper  
>> bitstruct initialization to the class under construction. It nicely  
>> encapsulates that operation which I believe demonstrates the Single  
>> Responsibility principle.
>> I hope this is of use to someone someday.
>> cr
>
> I think I see where you're going with that, but just so others know,  
> the hash-based initialization is simple (though it does require that  
> the hash keys match the field names--and avoiding this is probably  
> the point of your code):
>
> require 'bit-struct'
>
> hsh = { :context => 1, :password => "foo", :usr_name => "bar" }
>
> class C < BitStruct
>  signed :context, 32, "c id"
>  char :password, 12*8, "pw"
>  char :usr_name, 12*8, "name"
> end
>
> c = C.new hsh

Joel,

that's right. I probably shouldn't have used a hash as my example  
since you already have hash-based initialization built in. I meant for  
this to be a nice way to pass an arbitrary object to the constructor  
so the logic of getting data from that object would be encapsulated in  
one spot. I also could have built a temporary hash from the object  
argument and passed that to the superclass' constructor but I prefer  
the block-based initialization for readability.

And thanks for creating such a neat library. I don't have a need for  
it now that I understand my problem domain better, but rest assured it  
is now a member of my toolbox for some future problem when I do need it.

cr