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• MaybeChildSetter.scala

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com.raquo.laminar.setters.MaybeChildSetter.scala Maven / Gradle / Ivy

package com.raquo.laminar.setters

import com.raquo.airstream.core.Observable
import com.raquo.domtypes.generic.Modifier
import com.raquo.laminar.DomApi
import com.raquo.laminar.nodes.{ReactiveChildNode, ReactiveComment, ReactiveElement}
import com.raquo.laminar.setters.ChildrenSetter.Child
import org.scalajs.dom

class MaybeChildSetter(maybeNodeObservable: Observable[Option[Child]])
  extends Modifier[ReactiveElement[dom.Element]] {

  // @TODO[Elegance] Unify this logic with ChildSetter? Or not... Almost the same thing.

  override def apply(parentNode: ReactiveElement[dom.Element]): Unit = {
    val sentinelNode = new ReactiveComment("")
    var childNode: ReactiveChildNode[dom.Node] = sentinelNode

    // @TODO[Performance] In case of Signal we're doing append(comment)+replace(node), but we could do just one append(node)
    parentNode.appendChild(childNode)(DomApi.treeApi)
    parentNode.subscribe(maybeNodeObservable)(onNext)

    @inline def onNext(maybeNewChildNode: Option[Child]): Unit = {
      val newChildNode = maybeNewChildNode.getOrElse(sentinelNode)
      // @TODO[Performance] Add an "if (childNode != newChildNode)" check? Here or in replaceChild method?
      parentNode.replaceChild(childNode, newChildNode)(DomApi.treeApi)
      childNode = newChildNode
    }
  }
}