Retrofit2 에서 Rx사용시 Single 이 더 나을까?

출처 : https://stackoverflow.com/a/42005735

I'd suggest using a Single as it is more accurate representation of the data flow: you make a request to the server and the you get either one emission of data OR an error:

Single:     onSubscribe (onSuccess | onError)?

For an Observable you could theoretically get several emissions of data AND an error

Observable: onSubscribe onNext? (onCompleted | onError)?

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However, if you are using rx-java2, I'd suggest using a Maybe instead of Single. The difference between those two is that Maybe handles also the case when you get the response from server but it contains no body.

Maybe:      onSubscribe (onSuccess | onCompleted | onError)?