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From: Leo Alekseyev on 20 Mar 2010 04:02
Suppose I have a function foo which is a wrapper for bar. Both of
them have certain default options. Options[foo] includes some options
that should be passed to bar, which may override some of bar's
defaults, but if they are not provided bar should always receive some
default options.

Here are the definitions

ClearAll[foo];
ClearAll[bar];
Options[bar] = {barA -> 1, barB -> 2};
Options[foo] = {barA -> 11, barB -> 22, fooA -> 1};

And here is the desired output:
In[199]:= foo[] (* pass some default options to bar *)
Out[199]= bar[{barA -> 11, barB -> 22}]

In[200]:= foo[barA -> "overriding_barA"] (* overriding the default
option barA *)
Out[200]= bar[{barA -> "overriding_barA", barB -> 22}]

This situation commonly arises for me, and I've been using the
following implementation for foo[], which basically concatenates
supplied and default options and deletes duplicates, but I keep
thinking that there should be a better way. Is there?.. Am I missing
something obvious here?..

foo[opts : OptionsPattern[]] :=
Module[{},
bar[FilterRules[{opts}, Options[bar]]~Join~
FilterRules[Options[foo], Options[bar]] //
DeleteDuplicates[#, First[#1] == First[#2] &] &]]

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