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Questions tagged [kotlin]

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Is splitting Android activities/classes into many Kotlin extension functions a good or bad practise?

I have been working on an Android application for some time, and ever since the beginning I've developed a practice of splitting my class's (mostly activity/fragment) code up into multiple files. This ...
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-1 votes
1 answer
79 views

What is the relationship between Java Library and Kotlin?

I wanted to learn Kotlin but after reading online most experts seem to agree that learning Java first would be a first step in the roadmap of learning Kotlin. Their argument based on the fact that ...
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2 answers
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Which is the best approach I should follow use private fields in data class primary constructor or use Interfaces Inheritance?

I want to perform some operations on data class fields before accessing them and I am confused about which approach I should follow. I want to write code so that it makes sense to everyone and follows ...
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1 vote
1 answer
122 views

How to test functionality that requires a certain internal state?

I'm struggling to test functionality in a class where the class has to be in a certain state for the functionality to work, but the class cannot be put directly into a given state by design, to ...
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Android Compose, create an object wrapper for composable functions

I'm trying to create a kind of "form-bulder" with Compose, I've already done something similar with the old xml view system, and it was inspired by Django Forms. The things involved were a ...
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1 vote
2 answers
137 views

Is using KDoc/Javadoc comments inside of a function considered bad practice?

I often find it helpful to use KDoc/Javadoc comments inside of a class or function instead of normal comments. IntelliJ colorizes them more obviously by default and, more importantly, allows ...
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What's the proper way to avoid long parameter lists? [duplicate]

If I architect to utilize use-cases then I soon arrive at long param lists. As an example: class MainViewModel @Inject constructor( private val getUsers: GetUsers, private val deleteUser: ...
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2 answers
58 views

Approach for using multiple implementation of one interface for a single class, optional to use all or most of them

Consider an interface: interface Auth { fun doAuth() } this can be implemented for multiple APIs: class GoogleAuth : Auth { override fun doAuth(){ throw NoGoogleAuthImpl(); } } class ...
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-1 votes
3 answers
133 views

Interface or Object with Type?

I have a calculation program which uses a number of different vertex types. Currently I have euclidean and geo, and I have decided to create an interface. Now I am wondering if that is a good idea. ...
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4 votes
1 answer
136 views

Do kotlin libraries with inline APIs encourage high coupling and discourage unit testing?

As an example, let's assume our application needs some way to communicate with other systems using HTTP. interface HttpClient { fun <T> get(url: String, returnType: Class<T>): T fun ...
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18 votes
7 answers
7k views

Should one prefer a generic version of a function, even if it's not re-used (yet)?

YAGNI might tell us, that in the below implementation the generic version is not needed, as long as the function is only used once. But to me personally, it seems, the generic version is more readable ...
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1 vote
1 answer
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What is the reasoning behind Kotlin using non-nullable types for Java interop methods?

Considering Kotlin Java Interop: Null Safety and Platform Types Why is code like this legal in Kotlin? fun envString(key: EnvVars): String { return System.getenv(key.toString()) } getenv() can ...
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-2 votes
2 answers
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How to pass data between multiple project modules

I'm working on a Gradle project that has several modules. The project is implemented in Kotlin. One of these modules is the main entry point to the project, which is the main module. Another module ...
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0 answers
201 views

Common patterns for Observable data layer on iOS

I am working on learning native iOS development in Swift, and I am trying to find something that is similar to what I've learned in Android development with Kotlin. In particular I am referring to ...
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4 votes
2 answers
2k views

Why Kotlin doesn't allow assignments as expressions?

Coming from Java, I was surprised to find out that Kotlin doesn't allow assignments as expressions. Is there a reason for that? Java (Works) @Test public void test_x() { List<...
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1 vote
1 answer
207 views

Kotlin delegation, what should I test?

In Kotlin the powerful construct of delegation can be used to extend functionality of existing interfaces by reusing existing implementations. class Demo : Map by HashMap {} Questions: What should I ...
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12 votes
4 answers
8k views

When to write extension methods for your own classes?

I recently saw a code base which had a data class Address defined somewhere and then in a different place: fun Address.toAnschrift() = let { address -> Anschrift().apply { // mapping ...
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34 votes
3 answers
6k views

Why is there no static keyword in Kotlin?

Kotlin is known primarily as a drop-in replacement for Java, but it gets rid of a well-known Java construct: the static keyword. Instead, that class-level functionality is offered mainly by companion ...
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