title: ReactiveCocoa example with NSMutableArray push/pop?
body: <p>Could someone provide a one-line example of using ReactiveCocoa abstractions to achieve something like this:</p>
  
  <pre><code>// pseudo-code
  NSMutableArray *array = @[[] mutableCopy];
  RACSignal *newValue = RACAbleWithStart(array); // get whole array or maybe just added/removed element on push/pop
  
  [newValue subscribeNext:^(NSArray *x) {
    // x is whole array
  }]
  
  [newValue subscribeNext:^(id x) {
    // x is new value
  }]
  
  [newValue subscribeNext:^(id x) {
    // x is removed value
  }]
  </code></pre>
  
  <p>I see that some extensions for NSArray were removed in favor of Mantle <a href="https://github.com/ReactiveCocoa/ReactiveCocoa/pull/130">https://github.com/ReactiveCocoa/ReactiveCocoa/pull/130</a> But still can't find simple example of NSArray manipulation.</p>