sortedBy (original) (raw)

Returns a sequence that yields elements of this sequence sorted according to natural sort order of the value returned by specified selector function.

The sort is stable. It means that elements for which selector returned equal values preserve their order relative to each other after sorting.

The operation is intermediate and stateful.

Since Kotlin

1.0

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   class Dish(val name: String, val calories: Int, val tasteRate: Float) {
    override fun toString(): String = "Dish($name: <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>a</mi><mi>l</mi><mi>o</mi><mi>r</mi><mi>i</mi><mi>e</mi><mi>s</mi><mi>c</mi><mi>a</mi><mi>l</mi><mo separator="true">,</mo><mi>t</mi><mi>a</mi><mi>s</mi><mi>t</mi><mi>e</mi></mrow><annotation encoding="application/x-tex">calories cal, taste </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">c</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal" style="margin-right:0.02778em;">or</span><span class="mord mathnormal">i</span><span class="mord mathnormal">esc</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">a</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span></span></span></span>tasteRate/5)"
}

val fridgeContent = sequenceOf(Dish("🍨", 207, 4.7f), Dish("🥦", 34, 2.3f), Dish("🧃", 34, 4.9f))

val dullDishes = fridgeContent.sortedBy { it.tasteRate }
println(dullDishes.toList()) // [Dish(🥦: 34 cal, taste 2.3/5), Dish(🍨: 207 cal, taste 4.7/5), Dish(🧃: 34 cal, taste 4.9/5)]

val lightDishes = fridgeContent.sortedBy { it.calories }
// note that the sorting is stable, so the 🥦 is before the 🧃
println(lightDishes.toList()) // [Dish(🥦: 34 cal, taste 2.3/5), Dish(🧃: 34 cal, taste 4.9/5), Dish(🍨: 207 cal, taste 4.7/5)]

// the original sequence's state remains unchanged
println(fridgeContent.toList()) // [Dish(🍨: 207 cal, taste 4.7/5), Dish(🥦: 34 cal, taste 2.3/5), Dish(🧃: 34 cal, taste 4.9/5)] 
   //sampleEnd
}