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%% @copyright Copyright (c) 2010 Mochi Media, Inc.
%% @author David Reid <dreid@mochimedia.com>
%% @doc Utility functions for dealing with proplists.
-module(mochilists).
-author("David Reid <dreid@mochimedia.com>").
-export([get_value/2, get_value/3, is_defined/2, set_default/2, set_defaults/2]).
%% @spec set_default({Key::term(), Value::term()}, Proplist::list()) -> list()
%%
%% @doc Return new Proplist with {Key, Value} set if not is_defined(Key, Proplist).
set_default({Key, Value}, Proplist) ->
case is_defined(Key, Proplist) of
true ->
Proplist;
false ->
[{Key, Value} | Proplist]
end.
%% @spec set_defaults([{Key::term(), Value::term()}], Proplist::list()) -> list()
%%
%% @doc Return new Proplist with {Key, Value} set if not is_defined(Key, Proplist).
set_defaults(DefaultProps, Proplist) ->
lists:foldl(fun set_default/2, Proplist, DefaultProps).
%% @spec is_defined(Key::term(), Proplist::list()) -> bool()
%%
%% @doc Returns true if Propist contains at least one entry associated
%% with Key, otherwise false is returned.
is_defined(Key, Proplist) ->
lists:keyfind(Key, 1, Proplist) =/= false.
%% @spec get_value(Key::term(), Proplist::list()) -> term() | undefined
%%
%% @doc Return the value of <code>Key</code> or undefined
get_value(Key, Proplist) ->
get_value(Key, Proplist, undefined).
%% @spec get_value(Key::term(), Proplist::list(), Default::term()) -> term()
%%
%% @doc Return the value of <code>Key</code> or <code>Default</code>
get_value(_Key, [], Default) ->
Default;
get_value(Key, Proplist, Default) ->
case lists:keyfind(Key, 1, Proplist) of
false ->
Default;
{Key, Value} ->
Value
end.
%%
%% Tests
%%
-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").
set_defaults_test() ->
?assertEqual(
[{k, v}],
set_defaults([{k, v}], [])),
?assertEqual(
[{k, v}],
set_defaults([{k, vee}], [{k, v}])),
?assertEqual(
lists:sort([{kay, vee}, {k, v}]),
lists:sort(set_defaults([{k, vee}, {kay, vee}], [{k, v}]))),
ok.
set_default_test() ->
?assertEqual(
[{k, v}],
set_default({k, v}, [])),
?assertEqual(
[{k, v}],
set_default({k, vee}, [{k, v}])),
ok.
get_value_test() ->
?assertEqual(
undefined,
get_value(foo, [])),
?assertEqual(
undefined,
get_value(foo, [{bar, baz}])),
?assertEqual(
bar,
get_value(foo, [{foo, bar}])),
?assertEqual(
default,
get_value(foo, [], default)),
?assertEqual(
default,
get_value(foo, [{bar, baz}], default)),
?assertEqual(
bar,
get_value(foo, [{foo, bar}], default)),
ok.
-endif.
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