1. How to use timer with RxSwift
    • Problems with NSTimer
      • NSTimer will retain target which often cause retain cycle.
    • How to use timer with RxSwift 
         let o = Observable<Int>.timer(#dueTime, period: #lap?, scheduler: scheduler).subscribe()

   //DueTime is the the first time you will timer to fire
   //Lap is the inter-period between after fires, if nil is provided, the timer will only fire once. In this way you can create repeat timer and unrepeat timers
   //Scheduler: Scheduler where you will your timer to fire

   //Warning:The following timer will never fire unless you subscribe it.
   let o = Observable<Int>.timer(#dueTime, period: #lap?, scheduler: scheduler)

   //How to stop a timer? Just dipose the subscription
   let disposebal = Observable<Int>.timer(#dueTime, period: #lap?, scheduler: scheduler).sbuscribe()
   disposebal.dispose()
  2. When will subscription release in RxSwift?
    • Disposebal.dispose(by: disposeBag)
      • Subscription blocks(nextBlock, errorBlock) and the values retained by them will be released when disposeBag is released
      • Normally we create a disposeBag as a property of current object, when current object deinit, its disposeBag will also deinit, which cause all subscription blocks and value they retained to reduce reference count.
      • So if you retain Self in the blocks, onNext block for example, subscription and self retain each other, which will cause memory leak.
    • Observer.onError(error), onComplete()
      • If the observer calles its onError() or onComplete(), the subscription will also release
      • A common scene for this is the UI actions, when UI element deinit, their observables, button.rx.tap or collectionView.rx.modelSelected will also dispose
    • Edited: 2018-05-27
      • Another way to control dispose of your Subscription
    • Using takeUntil 
      //before you subscribe your observable, use takeUntil operator to make your observable dispose at a specific time
let o.takeUntil(self.rx.willDealloc).subscribe{#subscribeCode}
  3. How to use ssh key to communicate with remote repository
    • Create ssh keys pair
    • ssh-keygen
    • Default private key and public key is stored in ~/.ssh/ * Add to ssh agent
    • ssh-add ~/.ssh/private_key_file * Add ssh public key to repository holder
    • Github account preference * Test
    • ssh -T git@address_to_repository