Can't put PartialFunction in scala class constructor -


there appears restriction can't use partialfunction literals in class constructors:

scala> case class x(a: partialfunction[any, any]) { def this() = this({case x => x}) } <console>:7: error: implementation restriction: <$anon: => any> requires premature access class x.    case class x(a: partialfunction[any, any]) { def this() = this({ case x => x}) }

my first question why partial function literal need access "this". second question/observation in scala repl, running same code again crashes repl:

scala> case class x(a: partialfunction[any, any]) { def this() = this({ case x => x}) } java.lang.nullpointerexception     @ scala.tools.nsc.global$run.compilelate(global.scala:1595)     @ scala.tools.nsc.globalsymbolloaders.compilelate(globalsymbolloaders.scala:29)     @ scala.tools.nsc.symtab.symbolloaders$sourcefileloader.docomplete(symbolloaders.scala:369)     ...

and lastly, there workaround issue?

your first question answered in comment section of question

quoting imm:

anonymous classes have access enclosing class. compiler doesn't know anonymous partial function doesn't access (and hard check in full generality); disallows creating anonymous classes until you're class proper.

why crashes repl question, should submit ticket typesafe code example.

a workaround quite simple, define anonymous function outside of class compiler knows exact state closing over:

object x {   val default: partialfunction[any, any] = { case x => x } }  case class x(a: partialfunction[any, any]) {   def this() = this(x.default) }

Comments

Post a Comment

Popular posts from this blog

c# - Validate object ID from GET to POST -

i have method allows user access comment have made on site. have post method lets them update comment. my normal solution send entire comment model through, let them update it, update on database when post back. involve sending commentid through in hiddenfor , can manipulated. how can verify commentid sent in get method same i'm getting in post , not able alter comment wish? how can verify commentid sent in method same i'm getting in post? basically have validate following things in post - user logged-in user. authenticated users post comments. commentid in post , should valid commentid , should present in database. userid associated logged-in user should same userid associated comment . comment should contain userid column, can check @ time of update. to make sure update happens comment has been sent in get - hold commentid in session , in post action compare commentid value in session .
Read more

node.js - Custom Model Validator SailsJS -

when using custom model validator checks record within model. return within spread doesn't seem end control flow. //post.js model /** * custom validator **/ types: { isuservalid: function(user_id) { var promise = require('bluebird'); promise.all([ user.findone({id: user_id}) ]) .spread(function(user) { console.log(user); if (user === null || user === undefined) { console.log('failed'); return false; }else{ console.log('passed'); return true; } }); } }, my response standard validation failed response. { "error": "e_validation", "status": 400, "summary": "1 attribute invalid", "model": "post", "invalidattributes": { "owner": [ { "rule": "isuservalid", ...
Read more

php - Find a regex to take part of Email -

i have following emails need extract part from: bestellnummer xxx: 1 von xxx, 1er pack ------------- anfang der nachricht ------------- foo bar baz foo bar baz // <<<<< need text here ------------- ende der nachricht ------------- ------------- anfang der nachricht ------------- foo bar baz foo bar baz ------------- ende der nachricht ------------- there 0 unlimited occurences of ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- and i'm able extract first part regex: $re = "/------------- .*? -------------.?(.*?).?------------- .*? -------------/s"; but, i'm quite new on learning regex, i'm pretty sure there must better regex extract part (foo bar baz foo bar baz) of text between ------------- anfang der nachricht ------------- ------------- ende der nachricht ------------- as can in different languages, i'm using .? to match between hyphens. i...
Read more