Scala Snippet: How to filter a list in Scala

In Scala, filtering and processing collections is easy and elegant. There are many filtermethods available, but the most used will probably the basic filter method.

Here’s a code example of some filtering on my (ex)camera collection.
The filter method will not only work on Lists, but on any Scala collection.

 
object MyCameraCollection02 {
case class Camera(brand: String, model: String, sensorType: String, yearBought: Int) {
override def toString: String =
s"$brand $model \t\t $sensorType \t($yearBought)"
}
def main(args: Array[String]) {
val canon5dmarkIII = new Camera("Canon", "5D MkIII", "FF", 2013)
val canon5dmarkII = new Camera("Canon", "5D MkII", "FF", 2009)
val canon6d = new Camera("Canon", "6D", "FF", 2014)
val canon550d = new Camera("Canon", "550D", "APS-C", 2010)
val canon40d = new Camera("Canon", "40D", "APS-C", 2008)
val canonIXUS330 = new Camera("Canon", "IXUS 330", "1/2.7", 2001)
val canonIXUSZ90 = new Camera("Canon", "IXUS Z90", "APS-C", 1999)
val panasonicGM1 = new Camera("Panasonic", "GM1", "M43", 2014)
val panasonicFZ20 = new Camera("Panasonic", "FZ20", "1/2.5", 2005)
val sonyrx100 = new Camera("Sony", "DSC-RX100", "1\"", 2013)
val sonynex5 = new Camera("Sony", "NEX-5", "APS-C", 2011)
val sonyr1 = new Camera("Sony", "DSC-R1", "APS-C", 2005)
val myCameras = List(canon5dmarkIII, canon5dmarkII, canon6d, canon550d, canon40d, canonIXUS330, canonIXUSZ90, panasonicGM1, panasonicFZ20, sonyrx100, sonynex5, sonyr1)
val canonCameras = myCameras filter (_.brand == "Canon") // Every Canon camera I ever owned
val sonyCameras = myCameras filter (_.brand == "Sony") // Every Sony camera I ever owned
val pansonicCameras = myCameras filter (_.brand == "Panasonic") // Every Panasonic camera I ever owned
// apscCamera's only
val apscCameras = myCameras filter (_.sensorType == "APS-C")
println("==APS-C camera's owned==")
apscCameras foreach println
println()
// Canon camera's which are not full frame. You can filter, filtered lists.
val canonNonFF = myCameras filter (_.brand == "Canon") filter (_.sensorType != "FF")
println("==Non-FF camera's owned==")
canonNonFF foreach println
println()
// Filter by boolean expressions on class properties
val apsBefore2012 = apscCameras filter (_.yearBought < 2012)
println("==APS-C camera's bought before 2012 owned==")
apsBefore2012 foreach println
println()
// Filter by combining boolean expressions.
val ffcamerasBefore2012 = myCameras filter (cam => cam.yearBought < 2012 && cam.sensorType == "FF")
println("==Every FF Camera I ever owned before 2012==")
ffcamerasBefore2012 foreach println
println()
}
}

Running this example will give you the following result:

==APS-C camera's owned==
Canon 550D 		 APS-C 	(2010)
Canon 40D 		 APS-C 	(2008)
Canon IXUS Z90 		 APS-C 	(1999)
Sony NEX-5 		 APS-C 	(2011)
Sony DSC-R1 		 APS-C 	(2005)
==Non-FF camera's owned==
Canon 550D 		 APS-C 	(2010)
Canon 40D 		 APS-C 	(2008)
Canon IXUS 330 		 1/2.7 	(2001)
Canon IXUS Z90 		 APS-C 	(1999)
==APS-C camera's bought before 2012 owned==
Canon 550D 		 APS-C 	(2010)
Canon 40D 		 APS-C 	(2008)
Canon IXUS Z90 		 APS-C 	(1999)
Sony NEX-5 		 APS-C 	(2011)
Sony DSC-R1 		 APS-C 	(2005)
==Every FF Camera I ever owned before 2012==
Canon 5D MkII 		 FF 	(2009)

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