title: When to use RACReplaySubject vs. RACMulticastConnection?
body: <p>Using <a href="https://github.com/ReactiveCocoa/ReactiveCocoa" rel="noreferrer">ReactiveCocoa</a>, there seem to be two ways to have subscribers receive the same values from a signal, rather than re-triggering whatever operation generates those values: Via RACReplaySubject or RACMulticastConnection.</p>
  
  <p>Here are the header docs for RACReplaySubject:</p>
  
  <blockquote>
    <p>A replay subject saves the values it is sent (up to its defined capacity)
        and resends those to new subscribers. It will also replay an error or
        completion.</p>
  </blockquote>
  
  <p>And for RACMulticastConnection:</p>
  
  <blockquote>
    <p>A multicast connection encapsulates the idea of sharing one subscription to a
     signal to many subscribers. This is most often needed if the subscription to
     the underlying signal involves side-effects or shouldn't be called more than
     once.</p>
    
    <p>The multicasted signal is only subscribed to when
     <code>-[RACMulticastConnection connect]</code> is called. Until that happens, no values
     will be sent on <code>signal</code>. See <code>-[RACMulticastConnection autoconnect]</code> for how
     <code>-[RACMulticastConnection connect]</code> can be called automatically.</p>
    
    <p>Note that you shouldn't create RACMulticastConnection manually. Instead use
     <code>-[RACSignal publish]</code> or <code>-[RACSignal multicast:]</code>.</p>
  </blockquote>
  
  <p>Can someone provide simple <strong>guidelines as to when you would use RACReplaySubject or RACMulticastConnection</strong>?</p>