Scala动态列表排序 [英] Scala dynamic list sorting

问题描述

我正在寻找一种符合以下要求的动态排序列表的干净方法.

I'm looking for a clean way of dynamically sorting a list with the following requirements.

case class Person(name: String, middleName:Option[String], age:Integer) 

现在排序非常简单，但是，如果将这种排序从UI驱除，则用户将在其中进行列排序，而传递回服务器的参数将仅仅是列名.有什么建议可以动态创建此排序功能?

Now sorting that is pretty straight forward however if this sort is driven off a UI where a user would do column sorting and the parameters passed back to the server would simply be the column name. Any suggestions to dynamically create this sorting capability?

预先感谢

**已更新:

val sortByName = (p :Person) => p.name
val sortByMiddleName = (p: Person) => p.middleName

val mySortMap = Map("name" -> sortByName, "middleName" -> sortByMiddleName)

val sorted = persons.sortBy(mySortMap("name"))

**更新#2

import scala.math.Ordering.Implicits._

type PersonSorter = (Person, Person) => Boolean
val sortByName: PersonSorter = (x:Person, y:Person) => x.name < y.name
// Implicits import takes care of the Option here...
val sortByMiddleName: PersonSorter = (x:Person, y:Person) => x.middleName < y.middleName

val sortingMap: PersonSorter = Map[String, PersonSorter]("name" -> sortByName, "middleName" -> sortByMiddleName)

(排除年龄，但完全一样)

(Excluded age, but it's the exact same thing)

现在，当我有清单时，我可以轻松地做到这一点.

Now when I have my list, I can easily just do this.

persons.sortWith(sortingMap("name"))

其中名称"是从用户界面传入的参数字符串.

Where "name" is a parameter string passed in from the UI.

推荐答案

应该执行以下操作:

scala> val alice = Person("Alice", None, 20)
alice: Person = Person(Alice,None,20)

scala> val bob = Person("Bob", None, 21)
bob: Person = Person(Bob,None,21)

scala> val charlie = Person("Charlie", None, 18)
charlie: Person = Person(Charlie,None,18)

scala> val persons = List(alice, bob, charlie)
persons: List[Person] = List(Person(Alice,None,20), Person(Bob,None,21), Person(Charlie,None,18))

scala> persons.sortBy(p => (p.age, p.name))
res5: List[Person] = List(Person(Charlie,None,18), Person(Alice,None,20), Person(Bob,None,21))

scala> persons.sortBy(p => (p.name, p.age))
res6: List[Person] = List(Person(Alice,None,20), Person(Bob,None,21), Person(Charlie,None,18))

要按参数动态排序，您可以基于作为输入传递的参数定义自己的排序函数.因此，您可以编写一个函数，该函数返回传递给persons.sortBy的函数.传入的函数是排序函数，例如，可以通过sortByAge进行排序.如果您需要按两个或多个参数进行排序，这是相同的想法.

To dynamically sort by parameters you can define you own sort functions based on the parameters passed as input. So you could write a function that returns a function that is passed into persons.sortBy. That function passed in is the sorting function which could by sortByAge for example. It's the same idea if you need to sort by two or more parameters.

scala> val sortByAge = (p :Person) => p.age
sortByAge: Person => Integer = <function1>

scala> persons.sortBy(sortByAge)
res9: List[Person] = List(Person(Charlie,None,18), Person(Alice,None,20), Person(Bob,None,21))

这篇关于Scala动态列表排序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！