Solution: Blog Post Properties

data class BlogPost( val title: String, val content: String, val author: Author, ) { // Since this property is needed on average more than // once per blog post, and it is not expensive to // calculate, it is best to define it as a value. val authorName: String = "${author.name} ${author.surname}" // Since this property is needed on average more than // once per blog post, and it is expensive to // calculate, it is best to define it as a lazy val wordCount: Int by lazy { calculateWordCount() } // Since this property is needed on average less than // once per blog post, and it is not expensive to // calculate, it is best to define it as a getter. val isLongRead: Boolean get() = calculateIsLongRead() // Since this property is very expensive to calculate, // it is best to define it as a lazy val summary: String by lazy { generateSummary(content) } private fun calculateWordCount(): Int { Thread.sleep(1) return content.split("\\s+".toRegex()).size } private fun calculateIsLongRead(): Boolean { Thread.sleep(1) return content.length > 1000 } private fun generateSummary(content: String): String { Thread.sleep(10) return content.take(100) + "..." } }

import kotlin.system.measureTimeMillis data class BlogPost( val title: String, val content: String, val author: Author, ) { // Since this property is needed on average more than // once per blog post, and it is not expensive to // calculate, it is best to define it as a value. val authorName: String = "${author.name} ${author.surname}" // Since this property is needed on average more than // once per blog post, and it is expensive to // calculate, it is best to define it as a lazy val wordCount: Int by lazy { calculateWordCount() } // Since this property is needed on average less than // once per blog post, and it is not expensive to // calculate, it is best to define it as a getter. val isLongRead: Boolean get() = calculateIsLongRead() // Since this property is very expensive to calculate, // it is best to define it as a lazy val summary: String by lazy { generateSummary(content) } private fun calculateWordCount(): Int { Thread.sleep(1) return content.split("\\s+".toRegex()).size } private fun calculateIsLongRead(): Boolean { Thread.sleep(1) return content.length > 1000 } private fun generateSummary(content: String): String { Thread.sleep(10) return content.take(100) + "..." } } data class Author( val key: String, val name: String, val surname: String, ) fun main() { val post = BlogPost( title = "Hello, World!", content = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. " + "Sed non risus. Suspendisse lectus tortor, dignissim sit amet, " + "adipiscing nec, ultricies sed, dolor. Cras elementum ultrices diam. " + "Maecenas ligula massa, varius a, semper congue, euismod non, mi. " + "Proin porttitor, orci nec nonummy molestie, enim est eleifend mi, " + "non fermentum diam nisl sit amet erat. Duis semper. Duis arcu massa, " + "scelerisque vitae, consequat in, pretium a, enim. Pellentesque congue. " + "Ut in risus volutpat libero pharetra tempor. Cras vestibulum bibendum " + "augue. Praesent egestas leo in pede. Praesent blandit odio eu enim. " + "Pellentesque sed dui ut augue blandit sodales. Vestibulum ante ipsum " + "primis in faucibus orci luctus et ultrices posuere cubilia Curae; " + "Aliquam nibh. Mauris ac mauris sed pede pellentesque fermentum. " + "Maecenas adipiscing ante non diam sodales hendrerit.", author = Author( key = "alex", name = "Alex", surname = "Smith", ), ) // println(post.authorName) // // Alex Smith // println(post.wordCount) // // 153 // println(post.isLongRead) // // true // println(post.summary) // // Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed non risus. Suspendisse lectus tortor, dignissim sit amet, adipiscing nec, ultricies sed, dolor. Cras elementum ultrices diam. Maecenas ligula massa, varius a, semper congue, euismod non, mi. Proin portt... // Stress tests // val author = Author( // key = "alex", // name = "Alex", // surname = "Smith", // ) // val longText = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed non risus. Suspendisse lectus tortor, " + // "dignissim sit amet, adipiscing nec, ultricies sed, dolor. Cras elementum ultrices diam. Maecenas ligula massa, " + // "varius a, semper congue, euismod non, mi. Proin porttitor, orci nec nonummy molestie, enim est eleifend mi, non " + // "fermentum diam nisl sit amet erat. Duis semper. Duis arcu massa, scelerisque vitae, consequat in, pretium a, enim. " + // "Pellentesque congue. Ut in risus volutpat libero pharetra tempor. Cras vestibulum bibendum augue. Praesent egestas " + // "leo in pede. Praesent blandit odio eu enim. Pellentesque sed dui ut augue blandit sodales. Vestibulum ante ipsum " + // "primis in faucibus orci luctus et ultrices posuere cubilia Curae; Aliquam nibh. Mauris ac mauris sed pede pellentesque " + // "fermentum. Maecenas adipiscing ante non diam sodales hendrerit." // // measureTimeMillis { // val post = BlogPost( // title = "Hello, World!", // content = longText, // author = author, // ) // repeat(1_000_000) { post.authorName } // }.let { println("Reading authorName 1 000 000 times from the same object took $it") } // // measureTimeMillis { // repeat(1_000) { // val post = BlogPost( // title = "Hello, World!", // content = longText, // author = author, // ) // repeat(it % 11) { post.wordCount } // } // }.let { println("Reading wordCount from 1 000 objects from 0 to 10 times took $it") } // // measureTimeMillis { // repeat(10_000) { // val post = BlogPost( // title = "Hello, World!", // content = longText, // author = author, // ) // repeat(if (it % 4 == 0) 1 else 0) { post.wordCount } // } // }.let { println("Reading isLongRead from 10 000 objects 0, 0, 0, or 1 times took $it") } // // measureTimeMillis { // repeat(100) { // val post = BlogPost( // title = "Hello, World!", // content = longText, // author = author, // ) // repeat(it % 11) { post.summary } // } // }.let { println("Reading summary from 100 objects from 0 to 10 times took $it") } }