Adding new functionality with Kotlin's extension functions

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Currently, she's the lead Android developer at Off Grid Electric, where she works on implementing a next-generation Android mobile user interface, and reengineering the app to be resilient to spotty data coverage. We're going to use a property. And when you click on one of the planets, it takes you to this detailed view, where you get a description and other information about the planet, which includes its composition.

The default value is used when the corresponding argument is omitted from the function call. Creating an extension function You can define extension functions anywhere in your project, although to help keep everything organized you may want to place them inside a dedicated file. You will learn about arguments later in this article. Example of companion object In this example, we call a create function declared inside companion object using class name MyClass as qualifier.

Create an extension function

I started using Kotlin this week. Just as I can take something good like exercise and use it to justify a bad habit, we can take good Kotlin language features and use them to continue and exacerbate our bad Java coding habits into our Kotlin code. Collections belongs to the same breed. And the unpleasant part about these Utils-classes is that…class names are always getting in the kotlin extension function. The example they have for this is brilliant: list. And that, boys and girls, is where extension functions come from. An Example Extension Function Abuse In some cases, this seems like a great addition to the language. Where could we go wrong here. Its 484 lines long and has 33 methods. I still that that would be a mistake. Extension functions, as their name implies, are good for extending existing abstractions. SharedPreference is just an implementation detail. SharedPreferences can be a bit annoying to get a hold of, so to make matters worse, this bag of methods lives in an utility class. This has two consequences: First, SettingsUtil and AttendingFragment are harder to understand because they have low cohesion. Second, SettingsUtil and AttendingFragment are overly coupled, which will make testing and maintenance more difficult. Because the purpose of SettingsUtil is hard to understand, the purpose of AttendingFragment, a class that relies on it is also obscured, albeit to a lesser degree. This means that code that depends on extension methods are tightly coupled to a single implementation of an extension method. So, on both counts, using extension functions in this case merely helps us put lipstick on a pig. As I said at the outset of this section, extension functions are better used when we want to extend an already existing abstraction. Conference attendees accept a code of conduct that is presented in the ConductFragment. } Conclusion With these changes, the SettingsUtils class loses 5 kotlin extension function, thereby getting a little more digestible. The SharedPrefsAttendee implementation, as you can imagine, is short 24 kotlin lines and easily grokked. Classes that use the Attendee abstraction are a little clearer and a little simpler.

} The equivalent Java code would be: package foo. Mail us on hr javatpoint. How to create a user-defined function in Kotlin? Similarly, the type of second actual argument must match the type of second formal argument and so on. Conference attendees accept a code of conduct that is presented in the ConductFragment. This value is assigned to the variable result. A class which contains companion object can also be defined as extension function and property for the companion object. This is cool still printing from inside. I want to create an extension function and call it from Kotlin source only. What am I doing wrong?