diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 35924b0..1accd87 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -51,6 +51,7 @@ jobs:
 
       - name: Continuous Integration
         run: |
+          rebar3 xref
           rebar3 as test ci
 
       - name: Check if build left artifacts
diff --git a/README.md b/README.md
index 9b97331..453ca98 100644
--- a/README.md
+++ b/README.md
@@ -65,7 +65,7 @@ example project.
 % connects to the server via WebSocket.
 mount(#{assigns := Assigns} = Socket) ->
     Count = maps:get(count, Assigns, 0),
-    {ok, arizona_socket:assign(count, Count, Socket)}.
+    {ok, arizona_socket:put_assign(count, Count, Socket)}.
 
 % render/1 is called by the route to compile the template.
 % Macros substitutes variables.
@@ -117,10 +117,10 @@ render(Macros0) ->
 % Handle client events.
 handle_event(<<"incr">>, #{}, #{assigns := Assigns} = Socket) ->
     Count = maps:get(count, Assigns) + 1,
-    {noreply, arizona_socket:assign(count, Count, Socket)};
+    {noreply, arizona_socket:put_assign(count, Count, Socket)};
 handle_event(<<"decr">>, #{}, #{assigns := Assigns} = Socket) ->
     Count = maps:get(count, Assigns) - 1,
-    {noreply, arizona_socket:assign(count, Count, Socket)}.
+    {noreply, arizona_socket:put_assign(count, Count, Socket)}.
 
 %% --------------------------------------------------------------------
 %% Component functions.
diff --git a/include/arizona.hrl b/include/arizona.hrl
index a18836a..3dbe387 100644
--- a/include/arizona.hrl
+++ b/include/arizona.hrl
@@ -1,4 +1,3 @@
--define(ARIZONA_LIVEVIEW(Str), (begin
-    {ok, Tree} = arizona_live_view:parse_str(Str, Macros),
-    Tree
-end)).
+-define(ARIZONA_LIVEVIEW(Macros, Str), (
+    arizona_live_view:parse_str(Str, Macros)
+)).
diff --git a/src/arizona.erl b/src/arizona.erl
new file mode 100644
index 0000000..9ceec8a
--- /dev/null
+++ b/src/arizona.erl
@@ -0,0 +1,4 @@
+-module(arizona).
+
+-opaque payload() :: map().
+-export_type([payload/0]).
diff --git a/src/arizona_live_view.erl b/src/arizona_live_view.erl
index 3edbb76..110e605 100644
--- a/src/arizona_live_view.erl
+++ b/src/arizona_live_view.erl
@@ -32,12 +32,16 @@ Live view.
 -export([mount/2]).
 -export([handle_event/4]).
 
-%% TODO: Real types.
--type socket()  :: map().
--type macros()  :: map().
--type tree()    :: list().
--type event()   :: binary().
--type payload() :: map().
+-export([put_macro/3]).
+-ignore_xref([put_macro/3]).
+-export([get_macro/3]).
+-ignore_xref([get_macro/3]).
+
+-opaque macros() :: map().
+-export_type([macros/0]).
+
+-opaque tree() :: list().
+-export_type([tree/0]).
 
 %% Macros
 -define(PERSIST_KEY, ?MODULE).
@@ -46,14 +50,14 @@ Live view.
 %% Callbacks.
 %% --------------------------------------------------------------------
 
--callback mount(socket()) ->
-    {ok, socket()}.
+-callback mount(arizona_socket:t()) ->
+    {ok, arizona_socket:t()}.
 
 -callback render(macros()) ->
     tree().
 
--callback handle_event(event(), payload(), socket()) ->
-    {noreply, socket()}.
+-callback handle_event(EventName :: binary(), arizona:payload(), arizona_socket:t()) ->
+    {noreply, arizona_socket:t()}.
 
 -optional_callbacks([handle_event/3]).
 
@@ -61,9 +65,31 @@ Live view.
 %% API funtions.
 %% --------------------------------------------------------------------
 
+-spec put_macro(Key, Value, Macros) -> Macros
+  when Key :: atom(),
+       Value :: term(),
+       Macros :: macros().
+put_macro(Key, Value, Macros) ->
+  Macros#{
+    Key => maps:get(Key, Macros, Value)
+  }.
+
+-spec get_macro(Key, Macros, Default) -> Got
+  when Key :: atom(),
+       Macros :: macros(),
+       Default :: term(),
+       Got :: term().
+get_macro(Key, Macros, Default) ->
+  maps:get(Key, Macros, Default).
+
+-spec parse_str(Str, Macros) -> Parsed
+    when Str :: string() | binary(),
+         Macros :: macros(),
+         Parsed :: tree().
 parse_str(Str, Macros) ->
     {ok, Tokens, _EndLocation} = arizona_tpl_scan:string(Str),
-    arizona_tpl_parse:parse_exprs(Tokens, Macros).
+    {ok, Parsed} = arizona_tpl_parse:parse_exprs(Tokens, Macros),
+    Parsed.
 
 compile(Mod, Fun, Macros) ->
     arizona_tpl_compile:compile({Mod, Fun, Macros}).
@@ -109,7 +135,7 @@ parse_str_test() ->
 % Start parse_str support.
 
 render(Macros) ->
-    ?ARIZONA_LIVEVIEW("""
+    ?ARIZONA_LIVEVIEW(Macros, """
     <main :stateful>
         <h1>{_@title}</h1>
         <.arizona_live_view:counter/>
@@ -117,7 +143,7 @@ render(Macros) ->
     """).
 
 counter(Macros) ->
-    ?ARIZONA_LIVEVIEW("""
+    ?ARIZONA_LIVEVIEW(Macros, """
     <div :stateful>
         <div>{_@count}</div>
         <button type="button">Increment</button>
diff --git a/src/arizona_socket.erl b/src/arizona_socket.erl
index fb2afb6..d29f8a6 100644
--- a/src/arizona_socket.erl
+++ b/src/arizona_socket.erl
@@ -24,13 +24,20 @@ Components state.
 
 %% API functions.
 -export([new/3]).
--export([assign/2]).
--ignore_xref([assign/2]).
--export([assign/3]).
--ignore_xref([assign/3]).
+-export([put_assign/2]).
+-ignore_xref([put_assign/2]).
+-export([put_assign/3]).
+-ignore_xref([put_assign/3]).
+-export([get_assign/2]).
+-ignore_xref([get_assign/2]).
+-export([get_assign/3]).
+-ignore_xref([get_assign/3]).
 -export([push_event/3]).
 -export([prune/1]).
 
+-opaque t() :: map().
+-export_type([t/0]).
+
 %% --------------------------------------------------------------------
 %% API functions.
 %% --------------------------------------------------------------------
@@ -44,10 +51,15 @@ new(Id, View, Assigns) ->
         changes => #{}
     }.
 
-assign(Map, Socket) ->
-    maps:fold(fun assign/3, Socket, Map).
+put_assign(Map, Socket) ->
+    maps:fold(fun put_assign/3, Socket, Map).
 
-assign(Key, Value, #{assigns := Assigns, changes := Changes} = Socket) ->
+-spec put_assign(Key, Value, Socket) -> Socket
+    when Key :: atom(),
+         Value :: term(),
+         Socket :: t().
+put_assign(Key, Value, Socket) ->
+    #{assigns := Assigns, changes := Changes} = Socket,
     case Assigns of
         #{Key := Value} ->
             Socket;
@@ -58,6 +70,23 @@ assign(Key, Value, #{assigns := Assigns, changes := Changes} = Socket) ->
             }
     end.
 
+-spec get_assign(Key, Socket) -> Got
+    when Key :: atom(),
+         Socket :: t(),
+         Got :: term().
+get_assign(Key, Socket) ->
+    #{assigns := Assigns} = Socket,
+    maps:get(Key, Assigns).
+
+-spec get_assign(Key, Socket, Default) -> Got
+    when Key :: atom(),
+         Socket :: t(),
+         Default :: term(),
+         Got :: term().
+get_assign(Key, Socket, Default) ->
+    #{assigns := Assigns} = Socket,
+    maps:get(Key, Assigns, Default).
+
 push_event(Name, Payload, #{events := Events} = Socket) ->
     Socket#{events => [[Name, Payload] | Events]}.
 
diff --git a/test/arizona_live_view_SUITE.erl b/test/arizona_live_view_SUITE.erl
index b7b9ce2..04eefdc 100644
--- a/test/arizona_live_view_SUITE.erl
+++ b/test/arizona_live_view_SUITE.erl
@@ -64,7 +64,7 @@ mount(Socket) ->
     {ok, Socket}.
 
 render(Macros) ->
-    ?ARIZONA_LIVEVIEW(~s"""
+    ?ARIZONA_LIVEVIEW(Macros, ~s"""
     <html>
     <head>
     </head>