scrutinee is incompatible with pattern type; found : Option[String] required: String

[miki haiat]

I have issue with the return type from a for yield loop ,

i have this method and for some reason , i'm still new to scala...   im getting this error and a warning .

this is the method ,

def getPostMD(userID: String,url:String):Future[(Option[String],List[PostMD])]={
 
  val chunk: Future[JsValue] = Methods.getJsonValue(url)


    chunk.flatMap(ch => {
     val   postMd: Option[List[PostMD]] = (ch \ "data").asOpt[List[PostMD]]
      for{
         relatedPostMd:List[PostMD] <- postMd.get.filter(_.fromID == userID)        
         nextUrl: Option [String] <-(ch \ "paging" \ "next").asOpt[String]
        }yield(nextUrl,relatedPostMd)    
      }
}

the warning is ,

fruitless type test: a value of type PostMetaData.this.PostMD cannot also be a List[PostMetaData.this.PostMD] (the underlying of List[PostMetaData.this.PostMD])

and the error is ,

scrutinee is incompatible with pattern type; found : Option[String] required: String

What is wrong with my method  and what is  fruitless type ??

thanks,

miki

     

  

[Som Snytt]

Probably just remove the type annotations from the for comprehension.

for (i <- List(1,2,3)) ...

instead of

for (i: Int <- List(1,2,3))...

This is wrong:

for (i: List[Int] <- List(1,2,3))...

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[Som Snytt]

And, http://stackoverflow.com/q/27789412/1296806 shows more.