Is it possible to change Singleton (or any parameter) values after the initial Kodein instantiation?

I’d really like to be able to change the value of my HTTP clients baseUrl value, because it can be set dynamically while using the application. I’m having trouble finding a way to change parameter values dynamically.

I’ve looked into Multiton binding as it seemed like a type of Singleton-Factory that would allow the arguments to be changed. But I had no luck with that.

Here is my Api singleton:

interface LoginApi {

    @POST("Account/Login")
    @FormUrlEncoded
    fun login(
        @Field("username") username: String,
        @Field("password") password: String,
        @Field("sessionType") sessionType: String
    ): Call<BaseApiResponse<Login>>

    @GET("Account/Logout")
    fun logout(
        @Query("token") token: String
    ): Call<BaseApiResponse<Any>>

    companion object {
        operator fun invoke(
            baseUrl: String,
            cache: Cache
        ): LoginApi {

            val okHttpClient = OkHttpClient.Builder()
                .cache(cache)
                .readTimeout(60, TimeUnit.SECONDS)
                .connectTimeout(60, TimeUnit.SECONDS)
                .build()

            return Retrofit.Builder()
                .client(okHttpClient)
                .baseUrl(baseUrl)
                .addConverterFactory(JacksonConverterFactory.create())
                .build()
                .create(LoginApi::class.java)
        }
    }
}

Dependency Declaration with muliton (doesn’t work):

     import(androidXModule(this@MyApplication))

        bind<Any>() with multiton { baseUrl: String, applicationContext: Context ->
            createLoginApi(baseUrl, applicationContext)
            LoginApi(
                BuildConfig.BASE_URL,
                Cache(applicationContext.cacheDir, 10 * 1024 * 102)
            )
        }

        bind<LoginDataSource>() with singleton { LoginService(instance()) }
        bind<LoginRepository>() with singleton { LoginRepositoryImpl(instance()) }
        bind() from singleton { LoginViewModelFactory(instance()) }
        bind() from singleton { LoginViewModel(instance()) }
    }

Dependency Declaration with no multiton (works):

    import(androidXModule(this@MyApplication))

        bind() from singleton {
            LoginApi(
                BuildConfig.BASE_URL,
                Cache(applicationContext.cacheDir, 10 * 1024 * 102)
            )
        }

        bind<LoginDataSource>() with singleton { LoginService(instance()) }
        bind<LoginRepository>() with singleton { LoginRepositoryImpl(instance()) }
        bind() from singleton { LoginViewModelFactory(instance()) }
        bind() from singleton { LoginViewModel(instance()) }
    }

Version

    implementation 'org.kodein.di:kodein-di-generic-jvm:6.3.2'
    implementation "org.kodein.di:kodein-di-framework-android-x:6.3.2”

Let me know if you need any other information. This is pretty very simple example – I’d just like to be able to change parameter values dynamically. If that isn’t possible, then is there any way that would allow me to do such a thing

Thank you in advance!

[romainbsl]

that should work, but you’re code is not entirely decoupled.

bind<LoginApi>() with multiton { args: LoginArguments ->
    createLoginApi(args.baseUrl, applicationContext)
    LoginApi(
        args.baseUrl,
        Cache(applicationContext.cacheDir, 10 * 1024 * 102)
    )
}

bind<LoginDataSource>() with multiton { args: LoginArguments -> LoginService(instance(arg = args)) }

bind<LoginRepository>() with singleton { 
    LoginRepositoryImpl(instance(arg = LoginArguments(BuildConfig.BASE_URL)))
}

When retrieving the instance of LoginRepository Kodein will:

1. Look for a binding for LoginRepository
   • that’s the singleton with LoginRepositoryImpl waiting for a LoginDataSource
2. Look for LoginDataSource binding that need a parameter args: LoginArguments
   • that’s the multiton returning a LoginService with args: LoginArgumentsas parameter
     • this is the job of instance(arg = LoginArguments(BuildConfig.BASE_URL))

Hope this is clear enough.

[romainbsl]

Well, I get what you’re trying to do. There is no magic in Kodein, if you bind a multiton with some arguments, like:

bind<LoginApi>() with multiton { args: LoginArguments -> ... }

You can’t expect from Kodein to retrieve it with some dynamic values by applying the instance function, as you can have multiple instances to inject.

What you could do is to use another multiton, like:

bind<LoginDataSource>() with multiton { args: LoginArguments -> LoginService(instance(arg = args)) }

thus, the usage of LoginDataSource could be something like:

val dataSource: LoginDataSource by kodein.instance(arg = LoginArguments("/path", context))