I have a List of Map, each containing three key/value pairs:
List(
Map("id" -> 1, "key" -> 11, "value" -> 111),
Map("id" -> 2, "key" -> 22, "value" -> 222),
Map("id" -> 3, "key" -> 33, "value" -> 333),
Map("id" -> 4, "key" -> 44, "value" -> 444))
I would like to transform this to JSON but before that I need to remove the key and its value from every map and rename the value key to title. How can this be done in Scala in a elegant way?
You can do this:
val m1 = Map("id" -> 1, "key" -> 2, "value" -> 3)
val m2 = m1 - "key" // Map(id -> 1, value -> 3)
val m3 = m2 + ("title" -> m2("value")) - "value"
// Map(id -> 1, title -> 3)
So, for an entire list:
list.map(m => m + ("title" -> m("value")) - "value" - "key")
A similar approach to redefining the given list of maps, which fetches values of interest (an omits the rest),
mapsList.map { m => Map( "id" -> m("id"), "title" -> m("value") )}
Assuming you keys are String:
listOfMap map { m => (m - "key") + ("title" -> m("value")) - "value" }
That's to say for each element of the list (each m: Map), 1 create a copy without entry with key "key" (m - "key"), 2 create a second copy based on first one by appending a new entry with key "title" and value from entry with key "value" from original map m (+ ("title" -> m)), 3 and finally create finally map that will takes place in new list by removing entry for key "value" (finalizing the 'renaming': - "value").
I'd go with this
val list = ... // your definition
list map {
_ collect {
case ("value", v) => "title" -> v
case tpl @ (k, v) if k != "key" => tpl
}
}
