How to transfer variables between classes variables without creating a object second class inside first class?

Question

I have two classes. First is MainActivity.kt, where I have a some string. Second is a ServiceBuilder.kt like this

object ServiceBuilder {

    
    private const val URL = "https://someLink.com" // <------------- In here I should transfer the string in my MainActivity.kt class

    // Create Logger
    private val logger = HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY)

    // Create a Custom Interceptor to apply Headers application wide
    val headerInterceptor = object: Interceptor {

        override fun intercept(chain: Interceptor.Chain): Response {

            var request = chain.request()

            request = request.newBuilder()
                .addHeader("x-device-type", Build.DEVICE)
                .addHeader("Accept-Language", Locale.getDefault().language)
                .build()

            val response = chain.proceed(request)
            return response
        }
    }

    // Create OkHttp Client
    private val okHttp = OkHttpClient.Builder()
                                        .callTimeout(5, TimeUnit.SECONDS)
                                        .addInterceptor(headerInterceptor)
                                        .addInterceptor(logger)

    // Create Retrofit Builder
    private val builder = Retrofit.Builder().baseUrl(URL)
                                        .addConverterFactory(GsonConverterFactory.create())
                                        .client(okHttp.build())

    // Create Retrofit Instance
    private val retrofit = builder.build()

    fun <T> buildService(serviceType: Class<T>): T {
        return retrofit.create(serviceType)
    }
}

I need rightly transfer string from MainActivity to this object. I think creating MainActivity object inside ServiceBuilder is't good idea, because it allocate a superfluous memory. Using database or SharedPreferences is't good idea too, because this calls will slow down working program and this technologies was created for solving other problems.

Please tell my right way to solving this problem P.S. I now then this question is easy, but I don't now how to design app architecture

Answer 1

Yes, you are right. Placing MainActivity object inside ServiceBuilder is not a good idea. Instead, you can add such private field and function to initiate it to ServiceBuilder as a step of service building. Then you will be able to use it in buildService function

private var stringField: String? = null

fun fieldString(stringField: String): ServiceBuilder {
    this.stringField = stringField
    return this
}

And then use it from your activity as

    ServiceBuilder
        .fieldString("string to set")
        .buildService(...)

Also, you can review different moments regarding builder pattern in Kotlin here How to implement Builder pattern in Kotlin?