Clean_Code | Clean code and specification

Firstly, you must always return the cleaned value from a field clean method. Secondly, it is not safe to access other field values in a field clean method; that is what the overall clean() method is for.

You can save a query here. The return value of .first() on the queryset has all the info you need for your validation:

Just guessing here, but it seems that when the object that gsl::finally returns is destructed, it calls the lambda which free's the memory.

In the first case this returned object is assigned to the variable _ which is destructed once main returns. In the second case the object is destructed immediately after the call to gsl::finally, leading to any access to the memory afterwards being invalid.

flatMap operator is the thing you are looking for. You can emit the href links in a stream so that in flatMap operator you convert each link into a new observable which propagates its result into the original stream. I think this is exactly the behavior you described.

EDIT: Retrofit library provides nice interface to create observables from links. To elaborate more on your example, you first need to transform the collection object into some kind of Iterable using map operator. Once you have an interable, use flatMap to create an observable of items that belong to the Iterable using Observable.from(). This will emit the links as separate emissions. You then use flatMap again to transform each link into an observable of network request which forwards the emission back to the original stream.