<p>The ResultFilter acts like an “interface” that will allow you to …well, filter the results. A special method, called valid? will be invoked on each result (if such a filter is given to the KeywordTree).</p>
<p>Although defined in the extension, this class can be translated to Ruby code:</p>
<pre>
module AhoCorasick
class ResultFilter
# result => current result, Hash
# remain => what's left to be search, String
def valid?(result, remain)
end
end
end
</pre>
<p>So, filtering the results can be done then by extending this class and overwriting the <code>valid?</code> implementation.</p>
<p>At your convenience, the current <code>result</code> as well as the <code>remain</code> —ing string to be searched are passed as arguments to <code>valid?</code>.</p>
<pre>
class FooNotAllowed < AhoCorasick::ResultFilter
def valid?(result, remain)
result[:value] != "foo"
end
end
</pre>
<p>To attach a filter to the KeywordTree, use <code>filter=</code> method with your filter instance as argument.</p>
<p>Example:</p>
<p>Assuming a valid AhoCorasick::KeywordTree <code>tree</code>:</p>
<pre>
>> tree.filter= FooNotAllowed.new
=> #<FooNotAllowed:0x12d8a4c>
>> tree.add_string "foo"
=> 1
>> tree.add_string "bar"
=> 2
>> tree.add_string "baz"
=> 3
>> results= tree.find_all("foo is not bar")
=> [{:ends_at=>14, :starts_at=>11, :value=>"bar", :id=>2}]
</pre>
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