tulkdan.dev
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Kotlin/Classes.org
+51
Kotlin/Classes.org
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* Data classes
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Kotlin has *data classes* which have the same functionality as classes,
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but they come automatically with addtional member functions.
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These members functions allow you to easily print the instance to readable output,
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compare instances of a class, copy instances and more.
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To declare a data class, use the keyword =data=:
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#+begin_src kotlin
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data class User(val name: String, val id: Int)
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#+end_src
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The most useful predefined member functions of data classes are:
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| Function | Description |
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|---------------+-----------------------------------------------------------------------------------------|
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| =.toString()= | Prints a readable string of the class instance and its properties |
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| =.equals()= | Compares instances of a class |
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| =.copy()= | Creates a class instance by copying another, potentially with some different properties |
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#+begin_src kotlin
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import kotlin.random.Random
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data class Employee(val name: String, var salary: Int)
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class RandomEmployeeGenerator(var minSalary: Int, var maxSalary: Int) {
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val names = listOf("John", "Mary", "Ann", "Paul", "Jack", "Elizabeth")
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fun generateEmployee(): Employee {
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val name = names.random()
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val salary = Random.nextInt(from = minSalary, until = maxSalary)
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return Employee(name, salary)
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}
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}
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val empGen = RandomEmployeeGenerator(10, 30)
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println(empGen.generateEmployee())
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println(empGen.generateEmployee())
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println(empGen.generateEmployee())
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empGen.minSalary = 50
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empGen.maxSalary = 100
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println(empGen.generateEmployee())
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#+end_src
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#+RESULTS:
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: Employee(name=Paul, salary=12)
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: Employee(name=John, salary=22)
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: Employee(name=Ann, salary=13)
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: Employee(name=Jack, salary=74)