Why I can't access a method whose receiver is Test...

# getting-started

[Ayfri]

Why I can't access a method whose receiver is Test inside the class Test2 when inside a builder with Test ? But I can adding with of my instance of Test2.

class Test(var name: String = "test")

class Test2 {
    fun Test.method() = name
}

fun builder(block: Test.() -> Unit) = Test().apply(block)

fun main() {
    val a = Test2()
    
    builder {
        with(a) {
            println(method()) // can access method()
        }
        println(a.method()) // cannot access a.method() for some reason ?
    }
}

[Cody Mikol]

I think its because with is making the context of its lambda the this of a / Test2 which has an extension function with the ability to alter the context of the outer builder's this of class Test

[Cody Mikol]

you can do the same with apply

[Cody Mikol]

where in the builder's context you only have scope of the this of Test which has no definition of method

[Loney Chou]

Your definition of method implies that it's only callable (or to say "dottable") on Test but not Test2. a.method means you're calling method on Test2. This is where context receiver differs from common receiver. If you have context(Test) fun method() instead then you can a.method because Test is already in the context (from builder lambda). If you don't know what context receiver is, check this video:

https://www.youtube.com/watch?v=GISPalIVdQY▾

[Ayfri]

Thanks, I didn't think about using context receivers 🙂