http://iosdevlog.com/wwdc/2015/11/16/195196-wwdc2015-226-advanced-nsoperations/SummaryOperations abstract logicDependencies clarify intentDescribe complex behaviorsEnables powerful patternsOperationNSOperation subclass Adds “conditions” Adds “observers”Example operations* Groups* URLSessionTask* Location* DelayOperationConditionGenerates dependenciesDefines mutual exclusivityChecks for satisfied conditionsExample conditions* MutuallyExclusive* Reachability* PermissionsOperationObserverNotified about significant events* Operation start* Operation end* Operation generationExample observers* Timeouts* Background tasks* Network activity indicator
