The flatMap function is similar to map, but used a little differently.<\/p>\n
First, lets make a couple arrays:<\/p>\n
\nval x = List(1,2,3)\nval y = List(4,5,6)\n\nscala> List(x, y)\nres38: List[List[Int]] = List(List(1, 2, 3), List(4, 5, 6))\n\nscala> List(x, y).map( x => x )\nres40: List[List[Int]] = List(List(1, 2, 3), List(4, 5, 6))\n<\/pre>\nSometimes it’s preferable to get a flattened list, that looks like this:<\/p>\n
\nval z = List(1,2,3,4,5,6)\n<\/pre>\nWhich is what you do with flatMap:<\/p>\n
\nscala> List(x, y).flatMap( x => x )\nres41: List[Int] = List(1, 2, 3, 4, 5, 6)\n<\/pre>\nAn important thing to understand about flatMap is that anything that looks like an empty array will disappear, like so:<\/p>\n
\nList(None, Some(1), None, Some(2)).flatMap(x => x)\nres48: List[Int] = List(1, 2)\n<\/pre>\nNote that this does not recurse, so you may want to call it twice:<\/p>\n
\nList(\n List(None, Some(1)), \n List(None, Some(2))\n).flatMap(x => x)\n\nList[Option[Int]] = \n List(None, Some(1), None, Some(2))\n<\/pre>\n","protected":false},"excerpt":{"rendered":"The flatMap function is similar to map, but used a little differently. First, lets make a couple arrays: val x = List(1,2,3) val y = List(4,5,6) scala> List(x, y) res38: List[List[Int]] = List(List(1, 2, 3), List(4, 5, 6)) scala> List(x, y).map( x => x ) res40: List[List[Int]] = List(List(1, 2, 3), List(4, 5, 6)) Sometimes … <\/p>\n