Retrofit's `enqueue()` doesn't re-assign value of object in time for the return statement? - kotlin

Question

I'm making a call to the API and the response body is assigned to an object inside Retrofit's enqueue(), the problem is that enqueue finishes too quickly for the value to be assigned before the return statement of the function body is called.
Previously, I was using MutableLiveData before and it took care of that because it's always observing the data and when it changes it assigns it with no problem but now I don't want to use any MutableLiveData or Observables because I'm trying to prepare the data before any UI is actually drawn on the screen.
fun getResponse(
weatherLocationCoordinates: WeatherLocation
): RequestResponse {
weatherApiService.getCurrentWeather(
weatherLocationCoordinates.latitude,
weatherLocationCoordinates.longitude
).enqueue(object : Callback<WeatherResponse> {
override fun onResponse(
call: Call<WeatherResponse>,
response: Response<WeatherResponse>
) {
if (response.isSuccessful) {
// This where I do the assigning
requestResponse = RequestResponse(response.body(), true)
}
}
override fun onFailure(call: Call<WeatherResponse>, t: Throwable) {
requestResponse = RequestResponse(null, false)
}
})
// When this is called, enqueue is still not finished
// therefore I get the wrong value, I get the previously set initialization value of the obj.
return requestResponse
}
Should I be using Callbacks or something else? I'm not sure on how to implement the callback.

Answer 1

Following up on the comments here's an approach with callbacks:
Let's suppose we change the method signature to:
fun getResponse(
weatherLocationCoordinates: WeatherLocation,
onSuccess: (WeatherResponse) -> Unit = {},
onError: (Throwable) -> Unit = {}
) {
weatherApiService.getCurrentWeather(
weatherLocationCoordinates.latitude,
weatherLocationCoordinates.longitude
).enqueue(object : Callback<WeatherResponse> {
override fun onResponse(
call: Call<WeatherResponse>,
response: Response<WeatherResponse>
) {
if (response.isSuccessful) {
onSuccess(response.body())
} else {
onError(CustomHttpExceptionWithErrorDescription(response))
}
}
override fun onFailure(call: Call<WeatherResponse>, t: Throwable) {
onError(t)
}
})
}
CustomHttpExceptionWithErrorDescription will have to be something you code that can simply parse the error gotten from the server. Anything that is not 2XX status code
This method accepts 2 extra parameters - one gets called upon success the other on error. The idea is to call it like:
getResponse(
weatherLocationCoordinates,
onSuccess = {
// do something with response
},
onError = {
// do something with the error
}
)
Because they have default parameters you actually don't need to specify both callbacks. Just the one you are interested in. Examples:
// react only to successes
getResponse(
weatherLocationCoordinates,
onSuccess = {
// do something with response
}
)
// react only to errors
getResponse(weatherLocationCoordinates) {
// do something with the error
}
// just call the network calls and don't care about success or error
getResponse(weatherLocationCoordinates)