Update monarch.lua

Fixes #102

README_TRANSITIONS.md

@@ -114,7 +114,7 @@ end
 
 function on_message(self, message_id, message, sender)
 	if message_id == hash("my_resize_message") then
-		self.transition.window_resized(message.width, message.height)
+		transition.window_resized(message.width, message.height)
 	end
 end
 ```

monarch/monarch.lua

@@ -228,6 +228,17 @@ function M.is_visible(id)
 end
 
 
+--- Check if a screen is loaded
+-- @param id (string|hash)
+-- @return true if the screen is loaded
+function M.is_loaded(id)
+	assert(id, "You must provide a screen id")
+	id = tohash(id)
+	assert(screens[id], ("There is no screen registered with id %s"):format(tostring(id)))
+	return screens[id].loaded
+end
+
+
 --- Check if a screen is a popup
 -- @param id Screen id
 -- @return true if the screen is a popup
@@ -509,8 +520,12 @@ local function load(screen)
 		msg.post(screen.proxy, MSG_ENABLE)
 	elseif screen.factory then
 		screen.factory_ids = collectionfactory.create(screen.factory)
-		screen.transition_url = screen.factory_ids[screen.transition_id]
-		screen.focus_url = screen.factory_ids[screen.focus_id]
+		if screen.transition_id then
+			screen.transition_url = screen.factory_ids[screen.transition_id]
+		end
+		if screen.focus_id then
+			screen.focus_url = screen.factory_ids[screen.focus_id]
+		end
 	end
 	screen.loaded = true
 	screen.preloaded = false
@@ -1178,8 +1193,8 @@ end
 -- @return error (string|nil) Error message if unable to send message
 function M.post(id, message_id, message)
 	assert(id, "You must provide a screen id")
-	if not M.is_visible(id) then
-		return false, "Unable to post message to screen if it isn't visible"
+	if not M.is_loaded(id) then
+		return false, "Unable to post message to screen if it isn't loaded"
 	end
 
 	assert(message_id, "You must provide a message_id")

test/test_monarch.lua

@@ -155,6 +155,17 @@ return function()
 			assert(wait_until_visible(POPUP1))
 		end)
 
+		it("should be able to tell if a screen is loaded or not", function()
+			assert(not monarch.is_loaded(SCREEN1))
+			monarch.show(SCREEN1)
+			assert(wait_until_visible(SCREEN1))
+			assert(monarch.is_loaded(SCREEN1))
+			
+			monarch.hide(SCREEN1)
+			assert(wait_until_hidden(SCREEN1))
+			assert(not monarch.is_loaded(SCREEN1))
+		end)
+		
 		it("should be able to show a screen without adding it to the stack", function()
 			monarch.show(BACKGROUND, { no_stack = true })
 			assert(wait_until_visible(BACKGROUND), "Background was never shown")