I have Koin in my project, and I instantiate retrofit like this in the appmodule: ```single<ApiSe...

# koin

[Pablo]

I have Koin in my project, and I instantiate retrofit like this in the appmodule:

single<ApiService> {
    Retrofit.Builder()
        .baseUrl("<https://myurl.es>")
        .addConverterFactory(JacksonConverterFactory.create())
        .addConverterFactory(ScalarsConverterFactory.create())
        .build()
        .create(ApiService::class.java)
}

The issue is that I need to parametrize the baseUrl to retrofit, because the user can change it with a textfield. How can I tell Koin that must initialize this singleton for retrofit with a dinamically passed variable? I only found very complex samples for doing this using factory instead of singleton, and doing it with field injection instead of constructor injection, so I hope there is a simpler way.

[withoutclass]

The concept of singleton and also a parameterized dependency are not compatible.

You want a factory

[Pablo]

But I need that ApiService to be a singleton, to be a single instance injected in all the project

[Pablo]

and also, to be able to inject it on constructors

[Pablo]

not just in fields

[withoutclass]

I suggest using factory and the retrofit.newBuilder() api. Keep your retrofit as a singleton, then in your Api definition use a factory where you can pass the base url

[Pablo]

what do you mean with keep your retrofit as a singleton? also, I'm not sure I understand your last sentence, maybe a sample whould help

[withoutclass]

Investigate the Retrofit API, look for ways to solve “How do I change the URL of a Retrofit instance?”

Think about how you could utilize the same retrofit instance over and over while changing it’s URL

[CXwudi]

Why don't you just use interceptor in okhttp to dynamically set URL, this way you can still keep everything as Singleton
https://bbasoglu.medium.com/part-1-how-to-change-base-url-on-runtime-in-an-android-project-1d7607bbfa48

[Pablo]

are you sure that trick works? seems to be a little hack, also, not sure about the efficiency of that, seems to be building the connection each time? and how can I rebuilt it only if the interceptor has changed? even more, how can It detects has changed to rebuilt it?

[withoutclass]

Probably the better option here is to rethink your flow/UX. Alternatively you can load/unload your api koin module whenever the user changes the URL

[withoutclass]

Or just accept that you’re not going to have Singleton instances of your Api class. You can have singletons for your OkHttpClient and your Retrofit instance, and then a factory for your Api

[CXwudi]

Another way I could think of is using StateFlow, but that is too complicated.

About the interceptor way, I have one implemented at https://github.com/CXwudi/realworld-compose-http4k-example-app/blob/master/conduit-frontend/frontend-decompose-logic/src/commonMain/kotlin/mikufan/cx/conduit/frontend/logic/repo/api/setup.kt. I was using ktorfit and ktor. Ktor registered a plugin that does the URL setup, as well as token setup. I am not sure if this implementation makes sense to you, but at least it works well for me