configurable subtype selection (#57)

Author: fdietze

formidable/src/main/scala-2/Form-Scala2.scala

@@ -1,7 +1,6 @@
 package formidable
 
 import outwatch._
-import outwatch.dsl._
 import colibri.reactive._
 
 import magnolia1._
@@ -15,7 +14,7 @@ trait FormDerivation {
   def join[T](ctx: CaseClass[Typeclass, T]): Form[T] = new Form[T] {
     override def default: T = ctx.construct(param => param.default.getOrElse(param.typeclass.default))
 
-    override def render(state: Var[T], config: FormConfig): VModifier = Owned {
+    override def render(state: Var[T], config: FormConfig): VModifier = Owned.function { implicit owner =>
       val subStates: Var[Seq[Any]] =
         state.imap[Seq[Any]](seq => ctx.rawConstruct(seq))(_.asInstanceOf[Product].productIterator.toList)
 
@@ -38,26 +37,23 @@ trait FormDerivation {
       val defaultSubtype = ctx.subtypes.find(_.annotations.exists(_.isInstanceOf[Default])).getOrElse(ctx.subtypes.head)
       defaultSubtype.typeclass.default
     }
-    override def render(state: Var[T], config: FormConfig): VModifier = Owned {
-      val labelToSubtype =
-        ctx.subtypes.view.map { sub => sub.typeName.short -> sub }.toMap
+    override def render(selectedValue: Var[T], config: FormConfig): VModifier = Owned.function { implicit owner =>
 
-      div(
-        select(
-          ctx.subtypes.map { subtype =>
-            option(
-              subtype.typeName.short,
-              selected <-- state.map(value => ctx.split(value)(_ == subtype)),
-            )
-          }.toSeq,
-          onChange.value.map(label => labelToSubtype(label).typeclass.default) --> state,
+      val selectedSubtype: Var[Subtype[Form, T]] =
+        selectedValue.imap[Subtype[Form, T]](subType => subType.typeclass.default)(value => ctx.split(value)(identity))
+
+      config.unionSubform(
+        config.selectInput[Subtype[Form, T]](
+          options = ctx.subtypes,
+          selectedValue = selectedSubtype,
+          show = subtype => subtype.typeName.short,
         ),
-        state.map { value =>
+        subForm = selectedValue.map { value =>
           ctx.split(value) { sub =>
-            VModifier.when(value.isInstanceOf[T])(sub.typeclass.asInstanceOf[Form[T]].render(state, config))
+            VModifier.when(value.isInstanceOf[T])(sub.typeclass.asInstanceOf[Form[T]].render(selectedValue, config))
           }
         },
-      ): VModifier
+      )
     }
 
   }

formidable/src/main/scala-3/Form-Scala3.scala

@@ -1,7 +1,6 @@
 package formidable
 
 import outwatch._
-import outwatch.dsl._
 import colibri.reactive._
 
 import magnolia1._
@@ -13,7 +12,7 @@ trait FormDerivation extends AutoDerivation[Form] {
   override def join[T](ctx: CaseClass[Typeclass, T]): Form[T] = new Form[T] {
     override def default: T = ctx.construct(param => param.default.getOrElse(param.typeclass.default))
 
-    override def render(state: Var[T], config: FormConfig): VModifier = Owned {
+    override def render(state: Var[T], config: FormConfig): VModifier = Owned.function { implicit owner =>
       val subStates: Var[Seq[Any]] =
         state.imap[Seq[Any]](seq => ctx.rawConstruct(seq))(_.asInstanceOf[Product].productIterator.toList)
 
@@ -35,26 +34,25 @@ trait FormDerivation extends AutoDerivation[Form] {
       val defaultSubtype = ctx.subtypes.find(_.annotations.exists(_.isInstanceOf[Default])).getOrElse(ctx.subtypes.head)
       defaultSubtype.typeclass.default
     }
-    override def render(state: Var[T], config: FormConfig): VModifier = Owned {
-      val labelToSubtype =
-        ctx.subtypes.view.map { sub => sub.typeInfo.short -> sub }.toMap
-
-      div(
-        select(
-          ctx.subtypes.map { subtype =>
-            option(
-              subtype.typeInfo.short,
-              selected <-- state.map(value => ctx.choose(value)(_.subtype == subtype)),
-            )
-          }.toSeq,
-          onChange.value.map(label => labelToSubtype(label).typeclass.default) --> state,
+    override def render(selectedValue: Var[T], config: FormConfig): VModifier = Owned.function { implicit owner =>
+
+      val selectedSubtype: Var[SealedTrait.Subtype[Form, T, _]] =
+        selectedValue.imap[SealedTrait.Subtype[Form, T, _]](subType => subType.typeclass.default)(value =>
+          ctx.choose(value)(_.subtype),
+        )
+
+      config.unionSubform(
+        config.selectInput[SealedTrait.Subtype[Form, T, _]](
+          options = ctx.subtypes,
+          selectedValue = selectedSubtype,
+          show = subtype => subtype.typeInfo.short,
         ),
-        state.map { value =>
+        selectedValue.map { value =>
           ctx.choose(value) { sub =>
-            VModifier.when(value.isInstanceOf[T])(sub.typeclass.asInstanceOf[Form[T]].render(state, config))
+            VModifier.when(value.isInstanceOf[T])(sub.typeclass.asInstanceOf[Form[T]].render(selectedValue, config))
           }
         },
-      ): VModifier
+      )
     }
 
   }

formidable/src/main/scala/FormConfig.scala

@@ -65,6 +65,22 @@ trait FormConfig {
       validationMessage.map(_.map(msg => div(msg, color.red))),
     ): VModifier
   }
+
+  def selectInput[T](options: Seq[T], selectedValue: Var[T], show: T => String): VModifier = {
+    select(
+      Owned.function { implicit owner =>
+        options.zipWithIndex.map { case (opt, ind) =>
+          option(dsl.value := ind.toString)(
+            show(opt),
+            selectedValue.map(sel => selected := opt == sel),
+          )
+        }
+      },
+      onChange.value.map(index => options(index.toInt)) --> selectedValue,
+    )
+  }
+
+  def unionSubform(selectForm: VModifier, subForm: VModifier) = div(selectForm, subForm)
 }
 object FormConfig {
   val default: FormConfig = new FormConfig {}