[IMP] hooks: implement useRef hook

closes #194

src/qweb/context.ts

@@ -20,6 +20,7 @@ export class Context {
   shouldDefineParent: boolean = false;
   shouldDefineQWeb: boolean = false;
   shouldDefineUtils: boolean = false;
+  shouldDefineRefs: boolean = false;
   shouldDefineResult: boolean = true;
   shouldProtectContext: boolean = false;
   shouldTrackScope: boolean = false;
@@ -62,6 +63,9 @@ export class Context {
     if (this.shouldDefineResult) {
       this.code.unshift("    let result;");
     }
+    if (this.shouldDefineRefs) {
+      this.code.unshift("    context.__owl__.refs = context.__owl__.refs || {};");
+    }
     if (this.shouldDefineOwner) {
       // this is necessary to prevent some directives (t-forach for ex) to
       // pollute the rendering context by adding some keys in it.

src/qweb/extensions.ts

@@ -79,9 +79,10 @@ QWeb.addDirective({
   name: "ref",
   priority: 95,
   atNodeCreation({ ctx, value, addNodeHook }) {
+    ctx.rootContext.shouldDefineRefs = true;
     const refKey = `ref${ctx.generateID()}`;
     ctx.addLine(`const ${refKey} = ${ctx.interpolate(value)};`);
-    addNodeHook("create", `context.refs[${refKey}] = n.elm;`);
+    addNodeHook("create", `context.__owl__.refs[${refKey}] = n.elm;`);
   }
 });