fun <T> compareValuesBy( a: T, b: T, vararg selectors: (T) -> Comparable<*>? ): Int
Compares two values using the specified functions selectors to calculate the result of the comparison. The functions are called sequentially, receive the given values a and b and return Comparable objects. As soon as the Comparable instances returned by a function for a and b values do not compare as equal, the result of that comparison is returned.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
fun compareLengthThenString(a: String, b: String): Int =
compareValuesBy(a, b, { it.length }, { it })
println("compareLengthThenString("b", "aa") < 0 is ${compareLengthThenString("b", "aa") < 0}") // true
println("compareLengthThenString("a", "b") < 0 is ${compareLengthThenString("a", "b") < 0}") // true
println("compareLengthThenString("b", "a") > 0 is ${compareLengthThenString("b", "a") > 0}") // true
println("compareLengthThenString("a", "a") == 0 is ${compareLengthThenString("a", "a") == 0}") // true
//sampleEnd
}inline fun <T> compareValuesBy( a: T, b: T, selector: (T) -> Comparable<*>? ): Int
Compares two values using the specified selector function to calculate the result of the comparison. The function is applied to the given values a and b and return Comparable objects. The result of comparison of these Comparable instances is returned.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
fun compareLength(a: String, b: String): Int =
compareValuesBy(a, b) { it.length }
println("compareLength("a", "b") == 0 is ${compareLength("a", "b") == 0}") // true
println("compareLength("bb", "a") > 0 is ${compareLength("bb", "a") > 0}") // true
println("compareLength("a", "bb") < 0 is ${compareLength("a", "bb") < 0}") // true
//sampleEnd
}inline fun <T, K> compareValuesBy( a: T, b: T, comparator: Comparator<in K>, selector: (T) -> K ): Int
Compares two values using the specified selector function to calculate the result of the comparison. The function is applied to the given values a and b and return objects of type K which are then being compared with the given comparator.
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
fun compareInsensitiveOrder(a: Char, b: Char): Int =
compareValuesBy(a, b, String.CASE_INSENSITIVE_ORDER, { c -> c.toString() })
println("compareInsensitiveOrder('a', 'a') == 0 is ${compareInsensitiveOrder('a', 'a') == 0}") // true
println("compareInsensitiveOrder('a', 'A') == 0 is ${compareInsensitiveOrder('a', 'A') == 0}") // true
println("compareInsensitiveOrder('a', 'b') < 0 is ${compareInsensitiveOrder('a', 'b') < 0}") // true
println("compareInsensitiveOrder('A', 'b') < 0 is ${compareInsensitiveOrder('A', 'b') < 0}") // true
println("compareInsensitiveOrder('b', 'a') > 0 is ${compareInsensitiveOrder('b', 'a') > 0}") // true
//sampleEnd
}
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https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.comparisons/compare-values-by.html