ViewController transition bottleneck in UITabBarController

问题

When I tap on a specific UITabBarItem to switch ViewControllers, the transition takes about 4 - 5s.

There is no heavy processing being done, so this leads me to believe that the code is simply inefficient.

After having taken a look inside Instruments as suggested in the comments, I have pinpointed the following process to be taking ~> 2500 ms

Running Time    Self (ms)       Symbol Name
2485.0ms   44.3%    0.0     
TDescriptorSource::CopyDescriptorsForRequestFromArray(__CFArray const*, __CFDictionary const*, CFComparisonResult (*)(void const*, void const*, void*), void*, unsigned long, bool) const

and

Running Time    Self (ms)       Symbol Name
3070.0ms   54.7%    0.0      -[UIStackView initWithCoder:]

What does this mean?

来源：https://stackoverflow.com/questions/33963768/viewcontroller-transition-bottleneck-in-uitabbarcontroller