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added more DRY compareBy function and helper class

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This commit is contained in:
James Strachan
2012-09-14 12:44:09 +01:00
parent 51122a288d
commit 9c3d1071cd
3 changed files with 18 additions and 26 deletions
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libraries/stdlib/src/kotlin/OrderingJVM.kt
+6 -6
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@@ -6,14 +6,14 @@ import java.util.Comparator
* Helper method for implementing [[Comparable]] methods using a list of functions
* to calculate the values to compare
*/
inline fun <T> compareBy(a: T?, b: T?, vararg functions: Function1<T, Any?>): Int {
inline fun <T> compareBy(a: T?, b: T?, vararg functions: T.() -> Any?): Int {
require(functions.size > 0)
if (a === b) return 0
if (a == null) return - 1
if (b == null) return 1
for (fn in functions) {
val v1 = fn(a)
val v2 = fn(b)
val v1 = a.fn()
val v2 = b.fn()
val diff = compareValues(v1, v2)
if (diff != 0) return diff
}
@@ -47,12 +47,12 @@ public inline fun <T> compareValues(a: T?, b: T?): Int {
/**
* Creates a comparator using the sequence of functions used to calculate a value to compare on
*/
public inline fun <T> comparator(vararg functions: Function1<T,Any?>): Comparator<T> {
return FunctionComparator<T>(functions)
public inline fun <T> comparator(vararg val functions: T.() -> Any?): Comparator<T> {
return FunctionComparator<T>(*functions)
}
private class FunctionComparator<T>(val functions: Array<Function1<T,Any?>>): Comparator<T> {
private class FunctionComparator<T>(vararg val functions: T.() -> Any?): Comparator<T> {
public override fun toString(): String {
return "FunctionComparator${functions.toList()}"