scala - Avro Serialization from generics -


this simple example based on github page of avro4s, , works fine.

object main extends app {    case class ingredient(name: string, sugar: double, fat: double)   case class pizza(name: string, ingredients: seq[ingredient], vegetarian: boolean, vegan: boolean, calories: int)    val pepperoni = pizza("pepperoni", seq(ingredient("pepperoni", 12, 4.4), ingredient("onions", 1, 0.4)), false, false, 98)   val hawaiian = pizza("hawaiian", seq(ingredient("ham", 1.5, 5.6), ingredient("pineapple", 5.2, 0.2)), false, false, 91)    val format = recordformat[pizza]   val recordinavro = format.to(pepperoni)   printf(s"avro of pepperoni: $recordinavro\n") }

but this:

object main extends app {    case class ingredient(name: string, sugar: double, fat: double)   case class pizza(name: string, ingredients: seq[ingredient], vegetarian: boolean, vegan: boolean, calories: int)    val pepperoni = pizza("pepperoni", seq(ingredient("pepperoni", 12, 4.4), ingredient("onions", 1, 0.4)), false, false, 98)   val hawaiian = pizza("hawaiian", seq(ingredient("ham", 1.5, 5.6), ingredient("pineapple", 5.2, 0.2)), false, false, 91)    def toavro[t](obj: t): genericrecord = recordformat[t].to(obj)    val recordinavro = toavro[pizza](pepperoni)   printf(s"avro of pepperoni: $recordinavro\n") }

however, though last piece of code seems fine, following error during compilation time:

error:(14, 54) not find implicit value parameter torecord: com.sksamuel.avro4s.torecord[t]   def toavro[t](obj: t): genericrecord = recordformat[t].to(obj) error:(14, 54) not enough arguments method apply: (implicit torecord: com.sksamuel.avro4s.torecord[t], implicit fromrecord: com.sksamuel.avro4s.fromrecord[t])com.sksamuel.avro4s.recordformat[t] in object recordformat. unspecified value parameters torecord, fromrecord.   def toavro[t](obj: t): genericrecord = recordformat[t].to(obj)

any tips on how make avro serialisation work generics? thank you.

try change definition to

def toavro[t: torecord: fromrecord](obj: t): genericrecord = recordformat[t].to(obj)

more info here , here

in nutshell: when using concrete type compiler automatically find required torecord implicit value. in parameterized code should promise compiler supply implicit value somehow.


Comments

Post a Comment

Popular posts from this blog

What is happening when Matlab is starting a "parallel pool"? -

running parallel cpu processes in matlab starts command parpool() according documentation , function: [creates] special job on pool of workers, , [connects] matlab client parallel pool. this function takes bit of time execute, on order of 30 seconds. in other multi-cpu paradigms openmp, parallel execution seems totally transparent -- i've never noticed behavior analogous matlab (granted i'm not experienced parallel programming). so, happening between time parpool() called , when finishes executing? takes long? parallel computing toolbox enables run matlab code in parallel using several different paradigms (e.g. jobs , tasks, parfor , spmd , parfeval , batch processing), , run either locally (parallelised across cores in local machine) or remotely (parallelised across machines in cluster - either 1 own, or 1 in cloud). in of these cases, code run on matlab workers , copies of matlab without interactive desktop. if you're intending run on remo...
Read more

php - Cannot override Laravel Spark authentication with own implementation -

during login process of laravel spark need request token of remote api. api stores exact same users , passwords laravel spark application. therefore need username , non hashed password of user during authentication process. i thought overriding authenticated method solution problem. in routes/web.php override post /login endpoint , pointing endpoint own logincontroller: <?php namespace app\http\controllers\auth; use illuminate\support\facades\log; use illuminate\http\request; use laravel\spark\http\controllers\auth\logincontroller sparklogincontroller; class logincontroller extends sparklogincontroller { /** * create new login controller instance. * * @return void */ public function __construct() { parent::__construct(); } /** * handle successful authentication attempt. * * @param request $request * @param \illuminate\contracts\auth\authenticatable $user * @return response */ public fu...
Read more

Qt QGraphicsScene is not accessable from QGraphicsView (on Qt 5.6.1) -

i new qt. trying catch mouse press , release in qgraphicsview area , draw line. this, extended qgraphicsview , called myqgraphicsview . seems scene not attached since added " hello world " , never appears in view. here code extended class: class myqgraphicsview : public qgraphicsview { q_object public: myqgraphicsview(qgraphicsscene *scene, qwidget *parent = q_nullptr) : qgraphicsview(scene,parent){ // qgraphicsview::qgraphicsview(scene,parent); } qpoint *pointptr, *startpos,*endpos; qgraphicsview *cv;//maa qgraphicsscene *c; qgraphicsscene *sceneptr; // maa protected: void paintevent(qpaintevent *event) { show(); } void mousepressevent(qmouseevent *event) { // pos wrt widget. global wer global screen qdebug()<<" mouse pressed @ "<<qwidget::mapfromglobal(event->globalpos()); //globalx(); startpos = new qpoint; startpos->setx(qwidget::mapfromglobal(event->globalpos()).x()); startpos->sety(qw...
Read more