kotlin-extension

来源： https://stackoverflow.com/questions/64185390/kotlin-tostring-not-available-in-android-databinding

问题 I have multi module kotlin gradle project in github here. One of my sub project introducing-coroutines with build file build.gradle.kts file is here The contents of build.gradle.kts is - import org.jetbrains.kotlin.gradle.dsl.Coroutines import org.jetbrains.kotlin.gradle.tasks.KotlinCompile plugins { java kotlin("jvm") version "1.3.11" } group = "chapter2" version = "1.0-SNAPSHOT" repositories { mavenCentral() } dependencies { compile(kotlin("stdlib-jdk8")) compile("org.jetbrains.kotlinx

问题 I have multi module kotlin gradle project in github here. One of my sub project introducing-coroutines with build file build.gradle.kts file is here The contents of build.gradle.kts is - import org.jetbrains.kotlin.gradle.dsl.Coroutines import org.jetbrains.kotlin.gradle.tasks.KotlinCompile plugins { java kotlin("jvm") version "1.3.11" } group = "chapter2" version = "1.0-SNAPSHOT" repositories { mavenCentral() } dependencies { compile(kotlin("stdlib-jdk8")) compile("org.jetbrains.kotlinx

问题 I would like to restrict on which constant value extension function can be called. For example function like: @IdRes fun <T : View> Int.find() = findViewById<T>(this) If this was called on real id, it's fine: R.id.someView.find<TextView>() // ok But this should make compilation error: 42.find<TextView>() // should be compile error Is annotating extension receiver supported in Kotlin? 回答1: As described in the documentation, you can use the following syntax: fun @receiver:IdRes <T : View> Int

问题 I am working in Kotlin using a Kotlin-native library object containing a method whose .nameIsMuchTooLongAndIsStillNotClear . In a manner similar to typealias , I want to create an alias to the method, so I can refer to it as something .shortAndClear . To complicate matters slightly, these functions have several parameters, many of which have defaults that I'd prefer not to pre-process in a wrapper. After further research, it still seems like an extension function is the way to go. To use an

问题 I've just looked at Kotlin standard library and found some strange extension-functions called componentN where N is index from 1 to 5. There are functions for all types of primitives. For example: /** * Returns 1st *element* from the collection. */ @kotlin.internal.InlineOnly public inline operator fun IntArray.component1(): Int { return get(0) } It looks curiously for me. I'm interested in developers motives. Is it better to call array.component1() instead of array[0] ? 回答1: Kotlin has many

问题 Is it possible to create extension of final classes like String? Like in swift it is possible to add additional methods inside a extension of final class . For an example - I would like to create a method in String extension which will tell me String have valid length for password. val password : String = mEdtPassword!!.getText().toString() // how to define haveValidLength method in extension val isValid : Boolean = password.haveValidLength() Note - That example is just for a sake to

问题 I am trying to find a tail function in List<T> but I couldn't find any. I ended up doing this. fun <T> List<T>.tail() = this.takeLast(this.size -1) Is there a better way to do this? 回答1: Kotlin doesn't have a built-in List<T>.tail() function, so implementing your own extension function is the only way. Although your implementation is perfectly fine, it can be simplified a bit: fun <T> List<T>.tail() = drop(1) Or, instead of extension function, you can define an extension property: val <T>

问题 I have the following kotlin code: val urlPath = "https://10.0.2.2:8080" var data: String try { data = URL(urlPath).readText() } catch (e: Exception) { Log.e("doInBackground", "Exception caught: ${e.localizedMessage}") error = when (e) { is MalformedURLException -> "Invalid URL" is IOException -> "Network Error" else -> { "Network error: ${e.localizedMessage}" } } } If I use the above code to connect to a http server, the above code works. However when I try to connect to a https server with a

问题 I have the following kotlin code: val urlPath = "https://10.0.2.2:8080" var data: String try { data = URL(urlPath).readText() } catch (e: Exception) { Log.e("doInBackground", "Exception caught: ${e.localizedMessage}") error = when (e) { is MalformedURLException -> "Invalid URL" is IOException -> "Network Error" else -> { "Network error: ${e.localizedMessage}" } } } If I use the above code to connect to a http server, the above code works. However when I try to connect to a https server with a