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ViewsInitialize variables with ".()" expression in Kotlin
I'm using Ktor to make websocket requests.
The method "websocket(...)" I use takes two lambda expressions.
So as I only can call one with curly brackets I have to give the other one via a variable. So I tried this:
val request: HttpRequestBuilder.() -> Unit
val socket = ktorHttpClient.webSocket(request = request) {
}
The data types fit now but of course it still says "Variable 'request' must be initialized", so I tried to initialize it:
val request: HttpRequestBuilder.() -> Unit = HttpRequestBuilder.()
Now the error is gone but inside the last brackets it says "Expecting an expression", what am I missing here?
PS: Maybe there's even somebody who can explain in detail how initialization works when using ".()".
2 answers
Answer question0
As you said yourself, you need to pass two lambdas. You can do it either directly:
ktorHttpClient.webSocket({ /* request lambda */ }) {
/* block lambda */
}
Or split it as you did:
val request: HttpRequestBuilder.() -> Unit = { /* request lambda */ }
val socket = ktorHttpClient.webSocket(request) {
/* block lambda */
}
More info on how to initialize lambdas / function types can be found here: https://kotlinlang.org/docs/lambdas.html#instantiating-a-function-type
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Just use named parameters with lambdas:
ktorHttpClient.webSocket(request = {}, block = {})