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@@ -127,7 +127,7 @@ class Hash
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   #     #=> { :one => 1 }
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   def only(*allowed)
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     hash = {}
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-    allowed.each {|k| hash[k] = self[k] }
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+    allowed.each {|k| hash[k] = self[k] if self.has_key?(k) }
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     hash
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   end
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@@ -17,10 +17,12 @@ end
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 describe Hash, "only" do
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   before do
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-    @hash = { :one => 'ONE', 'two' => 'TWO', 3 => 'THREE' }
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+    @hash = { :one => 'ONE', 'two' => 'TWO', 3 => 'THREE', 4 => nil }
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   end
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   it "should return a hash with only the given key(s)" do
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+    @hash.only(:not_in_there).should == {}
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+    @hash.only(4).should == {4 => nil}
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     @hash.only(:one).should == { :one => 'ONE' }
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     @hash.only(:one, 3).should == { :one => 'ONE', 3 => 'THREE' }
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   end