CODEWITHSUNDEEP
kotlin
nicholas.hauschild
nicholas.hauschild

Reputation: 42849

Using receiver's infix function in lambda (for a DSL)

I'm working on creating a DSL using Kotlin, and I was hoping to utilize a receiver object with an infix function to get that groovy DSL feeling. I will start with an example of the syntax I am after:

myDslFunction { myReceiversInfixFunc "some string" }

My plan for achieving this was this code:

fun myDslFunction(builderFunction: MyReceiverObject.() -> Unit) {
    val receiver = MyReceiverObject()
    builderFunction(receiver)
    // do something with receiver
}

class MyReceiverObject {
    infix fun myReceiversInfixFunc(someString: String) {
        // do something with someString
    }
}

The function and class snippets above compiles fine, but the DSL syntax listed above doesn't. Here are some test functions I wrote to test the compilation:

fun test() {
    // desired syntax
    myDslFunction {
        myReceiversInfixFunc "some string" // doesn't compile
    }

    // not-desired syntax that compiles and works...
    myDslFunction { 
        this myReceiversInfixFunc "some string" // does compile
    }
}

The key difference here is the addition of the this keyword to setup the infix notation, but I would suggest that is undesired, and defeats the purpose of using the receiver object.

Is there something obvious I am missing here? Can I achieve my desired syntax? I wouldn't be surprised if I am overlooking a Kotlin convention to assist with doing this...

Upvotes: 3

Views: 802

Answers (1)

hotkey
hotkey

Reputation: 147981

You cannot achieve this syntax, because Kotlin only supports infix function calls where the receiver is explicitly specified: this myReceiversInfixFunc "someString".

There's a (quite old) language feature request for this syntax: KT-1292.

Upvotes: 2

Related Questions