В Scala фильтровать и обрабатывать коллекции легко и элегантно. Существует много доступных методов фильтрации, но наиболее часто используемым будет, вероятно, основной метод фильтрации.
Вот пример кода для фильтрации моей (бывшей) коллекции камер.
Метод filter будет работать не только со списками, но и с любой коллекцией Scala.
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object MyCameraCollection02 { class Camera(_brand: String, _model: String, _sensorType: String, _yearBought: Int) { val brand: String = _brand val model: String = _model val yearBought = _yearBought val sensorType = _sensorType override def toString(): String = { return "%s %s \t\t %s \t(%d)" format(brand, model, sensorType, 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(x => x.brand == "Canon") // Every Canon camera I ever owned val sonyCameras = myCameras.filter(x => x.brand == "Sony") // Every Sony camera I ever owned val pansonicCameras = myCameras.filter(x => x.brand == "Panasonic") // Every Panasonic camera I ever owned // apscCamera's only val apscCameras = myCameras.filter(cam => cam.sensorType == "APS-C") println("==APS-C camera's owned==") apscCameras foreach (cam => println(cam)) println // Canon camera's which are not full frame. You can filter, filtered lists. val canonNonFF = myCameras.filter(x => x.brand == "Canon").filter(x => x.sensorType != "FF") println("==Non-FF camera's owned==") canonNonFF foreach (cam => println(cam)) println // Filter by boolean expressions on class properties val apsBefore2012 = apscCameras.filter(cam => cam.yearBought < 2012) println("==APS-C camera's bought before 2012 owned==") apsBefore2012.foreach(cam => println(cam)) 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(cam => println(cam)) println }} |
Запуск этого примера даст вам следующий результат:
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==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) |
| Ссылка: | Scala Snippet: Как отфильтровать список в Scala от нашего партнера JCG Артура Артса в блоге JDriven . |