kotlin 編譯時常量

編譯時常數 (Compile-time Constant)

• If the value of a read-only (immutable) property is known at the compile time.

  如果在編譯時已知只讀(不可變)屬性的值。

• Mark it as a compile-time constant using the const modifier.

  使用const修飾符將其標記為編譯時常量。

• Such properties must be fulfilled by the following requirements.

  這些特性必須滿足以下要求。

  • Top-level, or member of an object declaration or a companion object.
  • Initialized with a value of type String or a primitive type
  • No custom getter

• No run time assignment allowed into const variables.

  不允許將運行時分配分配給const變量。

• The val keyword also used to make property immutable but the main difference between const and val is that properties declare with val can be initialized at runtime.

  val關鍵字還用于使屬性不可變，但是const和val之間的主要區別在于，可以在運行時初始化使用val聲明的屬性。

Kotlin中的編譯時常數程序 (Program for compile-time constant in Kotlin)

package com.includehelp//declare Top Level compile time constant const val PI=3.14//Declare Class with object to make singleton object Physics{//declare compile time constantconst val GRAVITY=10 }//declare class class Greetings{//declare companion objectcompanion object{//declare compile time constantconst val GREET="Hello IncludeHelp"} }//Main Function, Entry Point of Program fun main(){//Print All Constant Valueprintln("PI Value : $PI")println("Gravity : ${Physics.GRAVITY}")println("Greetings: ${Greetings.GREET}") }

Output:

輸出：

PI Value : 3.14 Gravity : 10 Greetings: Hello IncludeHelp

翻譯自: https://www.includehelp.com/kotlin/example-of-compile-time-constant.aspx

kotlin 編譯時常量

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