db:match

martinrehfeld · Dec 1, 2011 · 08bc056 · 08bc056
1 parent b1f51cc
commit 08bc056
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diff --git a/apps/warmup-database/src/db.erl b/apps/warmup-database/src/db.erl
@@ -29,7 +29,7 @@ read(Key, Db) ->
 
 %% @doc db:match(Element, Db) ⇒ [Key1, ..., KeyN].
 match(Element, Db) ->
-    [].
+    find(Element, Db).
 
 
 %% @private
@@ -39,3 +39,16 @@ get(Key, [{DifferentKey, Element}|T]) ->
     get(Key, T);
 get(Key, []) ->
     {error, instance}.
+
+%% @private
+find(Element, Db) ->
+    Matches = [],
+    find(Element, Db, Matches).
+
+find(Element, [{Key, Element}|T], Matches) ->
+    find(Element, T, Matches ++ [Key]);
+find(Element, [{DifferentKey, _Element}|T], Matches) ->
+    find(Element, T, Matches);
+
+find(Element, [], Matches) ->
+    Matches.
diff --git a/apps/warmup-database/test/db_tests.erl b/apps/warmup-database/test/db_tests.erl
@@ -29,3 +29,12 @@ read_hit_test() ->
     Db1 = db:write(ola, barcelona, Db),
     Db2 = db:write(oliver, berlin, Db1),
     ?assertEqual({ok, barcelona}, db:read(ola, Db2)).
+
+match_test() ->
+    Db = db:new(),
+
+    Db1 = db:write(francesco, london, Db),
+    Db2 = db:write(lelle, stockholm, Db1),
+    Db3 = db:write(joern, stockholm, Db2),
+
+    ?assertEqual([joern,lelle], db:match(stockholm, Db3)).