Null cache exception in FlatMap

I’m currently updating a project that was written under Binding.scala 10.0.3 (and compiled/ran fine) to 11.8.1. Updating the library caused a null error to surface that previously wasn’t there.

Specifically, in line 408 of Binding.scala, oldCache is null.

Looking through the changes to the relevant code since 10.0.03, I can see that this commit added a cache which is initialised to null.

Either there was some invariant that meant that oldCache should never be null (in which I need to fix my code) or a null check needs to be made.

[Atry]

Recursive code layout does not matter. What matters here is to avoid recursive Var changes.

Yang, Bo [e-mail]于2019年7月20日 周六下午1:54写道：

The oninput handler and the Future block are functions other than the @dom function. You know, their return types are not Binding, and they will be not triggered by Var or Vars changes.

Basim Khajwal [e-mail]于2019年7月20日 周六下午12:52写道：

Right, I understand.

One thing I’m still unsure about is the typical pattern for input elements which goes like:

import org.scalajs.dom.html

@dom def inputElement(data: Var[String]): Binding[html.Input] = { <input oninput={e:Event => data.value = e.target.asInstanceOf[html.Input].value} value={data.bind} /> }

This is still a recursive binding that works however it still invalidates the principle that value_= should never be called within a @dom expression.

Moving the oninput to an external function kind of resolves it but it still effectively does the same thing (recursive) so I’m still unsure as to how to properly handle this situation (if there is an alternative).

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[Atry]

The oninput handler and the Future block are functions other than the @dom function. You know, their return types are not Binding, and they will be not triggered by Var or Vars changes.

Basim Khajwal [e-mail]于2019年7月20日 周六下午12:52写道：

Right, I understand.

One thing I’m still unsure about is the typical pattern for input elements which goes like:

import org.scalajs.dom.html

@dom def inputElement(data: Var[String]): Binding[html.Input] = { <input oninput={e:Event => data.value = e.target.asInstanceOf[html.Input].value} value={data.bind} /> }

This is still a recursive binding that works however it still invalidates the principle that value_= should never be called within a @dom expression.

Moving the oninput to an external function kind of resolves it but it still effectively does the same thing (recursive) so I’m still unsure as to how to properly handle this situation (if there is an alternative).

— You are receiving this because you commented.

Reply to this email directly, view it on GitHub https://github.com/ThoughtWorksInc/Binding.scala/issues/188?email_source=notifications&email_token=AAES3OVAJZ5OVAKNDPTVZN3QANUG7A5CNFSM4IFM5H52YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD2NU4DA#issuecomment-513494540, or mute the thread https://github.com/notifications/unsubscribe-auth/AAES3OU4GZSQYPHEIYTGY2DQANUG7ANCNFSM4IFM5H5Q .

– 杨博 (Yang, Bo)