Add Signal.get to simplify the innerFlare type

Author: koterpillar

html/index.html

@@ -175,7 +175,7 @@ <h3>Example 14: Color picker (running Flare inside Flare)</h3>
                   <*> is "Green"   0
                   <*> is "Blue"  100
 
-ui = traverse_ toHTML <$>
+ui = toHTML <$>
      select "Color domain" (HSL :| [RGB]) showDomain `innerFlare` uiColor
 </pre>
         <div id="controls14"></div>

src/Flare.js

@@ -35,6 +35,12 @@ exports.createInnerElementP = function(tuple) {
   };
 };
 
+exports.get = function (sig) {
+  return function () {
+    return sig.get();
+  };
+};
+
 exports.appendComponent = function(target) {
   return function(el) {
     return function() {

src/Flare.purs

@@ -449,19 +449,24 @@ flareWith controls handler (UI setupUI) = do
 -- | Renders an UI with access to the current value.
 innerFlare :: forall e a b. UI e a
            -> (a -> UI e b)
-           -> UI e (Maybe b)
+           -> UI e b
 innerFlare (UI setupUI) innerUI = UI $ do
   (Flare components signal) <- setupUI
+  -- Get the initial value for the resulting signal
+  UI setupInnerUI <- innerUI <$> get signal
+  (Flare _ innerSignal) <- setupInnerUI
+  initialInner <- get innerSignal
+  innerResult <- channel initialInner
+  -- Set up the inner UI
   Tuple innerHostId innerHost <- createInnerElement
-  -- FIXME: there's no way to create a channel without a value, and no way to
-  -- get the current value out of signal, thus Maybe in the type
-  --
-  -- innerResult <- channel $ innerUI $ get signal
-  innerResult <- channel Nothing
-  let setupInner = innerUI >>> flareWith innerHostId (map (Just >>> send innerResult) >>> S.runSignal)
+  let setupInner = innerUI >>> flareWith innerHostId (map (send innerResult) >>> S.runSignal)
   S.runSignal $ setupInner <$> signal
   pure $ Flare (components <> [innerHost]) (subscribe innerResult)
 
+-- | Get the current value of a signal. Should be in purescript-signal, pending
+-- https://github.com/bodil/purescript-signal/pull/60
+foreign import get :: forall e a. S.Signal a -> Eff e a
+
 -- | Renders a Flare UI to the DOM and sets up all event handlers. The ID
 -- | specifies the HTML element to which the controls are attached. The
 -- | function argument will be mapped over the `Signal` inside the `Flare`.

test/Main.purs

@@ -181,7 +181,7 @@ uiColor RGB = rgb <$> is "Red"   200
                   <*> is "Blue"  100
 
 ui14 :: forall e m. UI e (H.Markup m)
-ui14 = traverse_ toHTML <$>
+ui14 = toHTML <$>
        select "Color domain" (HSL :| [RGB]) showDomain `innerFlare` uiColor
 
 -- Example 15