map和flatMap

 

scala> val a  = Seq(1,2,3,6,4)a: Seq[Int] = List(1, 2, 3, 6, 4)scala>     val b = a.flatMap(f=>{     |       try{     |         Some(f/(f-1))     |       }catch{     |         case e:Exception=>None     |       }     |     })b: Seq[Int] = List(2, 1, 1, 1)scala>     val b = a.map(f=>{     |       try{     |         Some(f/(f-1))     |       }catch{     |         case e:Exception=>None     |       }     |     })b: Seq[Option[Int]] = List(None, Some(2), Some(1), Some(1), Some(1))

 

 

flatMap类型需要一致

scala>     val d = a.flatMap(f=>{     |       try{     |         f/(f-1)     |       }catch{     |         case e:Exception=>None     |       }     |     })
     
      :33: error: type mismatch; found   : Int required: scala.collection.GenTraversableOnce[?]               f/(f-1)                ^scala>     val d = a.map(f=>{     |       try{     |         f/(f-1)     |       }catch{     |         case e:Exception=>None     |       }     |     })d: Seq[Any] = List(None, 2, 1, 1, 1)