I have a Seq of objects (protobuf objects). I would like to iterate through the list, where a specific field value is filtered, and update these specific objects in the original list.

For example:

val serversProto = Seq(...)

serversProto = serversProto
  .filter(server => server.registrationStatus == "REGISTERED")
  .map(server => 
    ... update server object
  )

The problem with the above is that serverProtos is now a filtered list ONLY containing items that matched the filter. What I want to do is update the items in serversProto where the filter is true, but keep all the other original items.

Is this possible?

I have a Seq of objects (protobuf objects). I would like to iterate through the list, where a specific field value is filtered, and update these specific objects in the original list.

For example:

val serversProto = Seq(...)

serversProto = serversProto
  .filter(server => server.registrationStatus == "REGISTERED")
  .map(server => 
    ... update server object
  )

The problem with the above is that serverProtos is now a filtered list ONLY containing items that matched the filter. What I want to do is update the items in serversProto where the filter is true, but keep all the other original items.

Is this possible?

• scala

• 2 Why not map with if-else and modify only items that match the predicate? – Mateusz Kubuszok Commented Jan 18 at 23:41
• @MateuszKubuszok did not think of that, thanks, that worked – Kris Rice Commented Jan 18 at 23:45
• @MateuszKubuszok please post as an answer with an example – Kris Rice Commented Jan 18 at 23:45
• Why will a filter pipeline keep things which do not map filter. Your question should be "How do I update only items which match a filter" ? – sarveshseri Commented Jan 19 at 7:01

1 Answer 1

There is a few option, one of the option is more easy to understand, like Mateusz Kubuszok told above.

1. Using map with IF - ELSE,

    val withMap = serversProto.map(server => 
      if (server.registrationStatus == "REGISTERED") {
        server.copy(name = s"${server.name}-updated")
      } else {
        server
      }
    )

2. Using map with Pattern Matching

    val withPatternMatch = serversProto.map {
      case server if server.registrationStatus == "REGISTERED" =>
        server.copy(name = s"${server.name}-updated")
      case server => server
    }

3. Using collect

    val withCollect = serversProto.collect {
      case server if server.registrationStatus == "REGISTERED" =>
        server.copy(name = s"${server.name}-updated")
      case server => server
    }

But I recommend using no. 3, because its more clean and simple and more idiomatic in scala