Kotlin in Action teaches you to use the Kotlin language for production-quality applications. = null) fun main(args: Array) { val persons = listOf(Person("Alice"), Person("Bob", age = 29)) val oldest = persons.maxBy { it.age ? Submit Close. 8 Higher-Order Functions: Lambdas as Parameters and Return Values. Kotlin in Action teaches you to use the Kotlin language for production-quality applications. Kotlin in Action guides experienced Java developers from the language basics of Kotlin all the way through building applications to run on the JVM and Android devices. .. Kotlin is fun and easy to learn when you have this book to guide you! () -> Unit) fun negativeButton(text: String, callback: DialogInterface. First, conciseness Functional code can be more elegant and succinct compared to its imperative counterpart, because working with functions as values gives you much more power of abstraction, which lets you avoid duplication in your code Imagine that you have two similar code fragments that implement a similar task (for example, looking for a matching element in a collection) but differ in the details (how the matching element is detected) You can easily extract the common part of the logic into a function and pass the differing parts as parameters Those parameters are themselves functions, but you can express them using a concise syntax for anonymous functions called lambda expressions: fun findAlice() = findPerson { it.name == "Alice" } fun findBob() = findPerson { it.name == "Bob" } findPerson() contains the general logic of finding a person The block in curly braces identifies the specific person you need to find The second benefit of functional code is safe multithreading One of the biggest sources of errors in multithreaded programs is modification of the same data from multiple threads without proper synchronization If you use immutable data structures and pure functions, you can be sure that such unsafe modifications won’t happen, and you don’t need to come up with complicated synchronization schemes Finally, functional programming means easier testing Code without side effects is usually easier to test Functions can be tested in isolation without requiring a lot of setup code to construct the entire environment that they depend on Generally speaking, the functional style can be used with any programming language, including Java, and many parts of it are advocated as good programming style But not all languages provide the syntactic and library support required to use it effortlessly; for example, this support was mostly missing from versions of Java before Java Kotlin has a rich set of features to support functional programming from the get-go These include the following: Functional types, allowing functions to receive other functions as parameters or return other functions Lambda expressions, letting you pass around blocks of code with minimum boilerplate Data classes, providing a concise syntax for creating immutable value objects A rich set of APIs in the standard library for working with objects and collections in the functional style Kotlin lets you program in the functional style but doesn’t enforce it When you need it, you can work with mutable data and write functions that have side effects without jumping through any extra hoops And, of course, working with frameworks that are based on interfaces and class hierarchies is just as easy as with Java When writing code in Kotlin, you can combine both the object-oriented and functional approaches and use the tools that are most appropriate for the problem you’re solving taking "USA" as an argument, and you can correctly guess that it’s another member extension Here we again come across an extension method on Column that is also a member and thus can be used only in the appropriate context, for instance when specifying the condition of the select method The simplified declarations of the select and eq methods are below: fun Table.select(where: SqlExpressionBuilder. Thorough, well written, and easily accessible. Kotlin in Action MEAP V11 - … : returns zero if age is null Because Alice’s age isn’t specified, the Elvis operator replaces it with zero, so Bob wins the prize of being the oldest person Do you like what you’ve seen? : } } println("The oldest is: $oldest") // The oldest is: Person(name=Bob, age=29) 'data' class nullable type (Int? Reason. Contribute to abel533/Kotlin-in-action development by creating an account on GitHub. ); default value for argument top-level function named argument lambda expression; "elvis" operator string template autogenerated 'toString' You declare a simple data class with two properties: name and age The age property is null by default (if it isn’t specified) When creating the list of people, you omit Alice’s age, so the default value null is used Then you use the function maxBy to find the oldest person in the list The lambda expression passed to the function takes one parameter, and you use it as the default name of that parameter The Elvis operator ? Description. Report "Kotlin in Action v12 MEAP" Please fill this form, we will try to respond as soon as possible. Slideshare: Is there a more productive and concise alternative to Java? pBook + eBook With Kotlin, you can implement your projectswithlesscode,ahigherlevelofabstraction,andfewer annoyances. Design by 123DOC, - MEAP Edition Manning Early Access Program Kotlin in Action Version 11 Copyright 2016 Manning Publications For more information on this and other Manning titles go to www.manning.com Welcome Thanks for purchasing the MEAP for Kotlin in Action! ", message = "Are you really sure?") It’s a new programming language targeting the Java platform Kotlin is concise, safe, pragmatic, and focused on interoperability with Java code It can be used almost everywhere Java is used today - for server-side development, Android apps, and much more Kotlin works great with all existing Java libraries and frameworks and runs with the same level of performance as Java Let’s start with a small example to demonstrate what Kotlin looks like This example defines a Person class, creates a collection of people, finds the oldest one, and prints the result Even in this small piece of code, you can see many interesting features of Kotlin; we’ve highlighted some of them so you can easily find them later in the book The code is explained briefly, but please don’t worry if something isn’t clear right away We’ll discuss everything in detail later If you’d like to try running this example, the easiest option is to use the online playground at https://try.kotl.in/ Type in the example and click the Run button, and the code will be executed Here’s the code: data class Person(val name: String, val age: Int?

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