xcode 编译opencv ios容易出现的错误

（1）出现 "std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush()"之类的错误

Undefined symbols for architecture i386:
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::flush()", referenced from:
      cv::gpu::error(char const*, char const*, int, char const*) in opencv2(gpumat.o)
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::sentry(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<< <std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*) in opencv2(gpumat.o)
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::sentry::~sentry()", referenced from:
      std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::operator<< <std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*) in opencv2(gpumat.o)
  "std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(int)", referenced from:
      cv::gpu::error(char const*, char const*, int, char const*) in opencv2(gpumat.o)
  "std::__1::cerr", referenced from:

解决办法是加入c++库 ，想项目中加入libc++.dylib

1. Select your project (the blue file) in your project navigator (Command 1 if it's hidden)
2. Select your target
3. Go to Build Phases
4. Expand "Link Binary With Libraries"
5. Click the "+"
6. Type libc++.dylib in the search bar.
7. Select the libc++.dylib file and press "Add"

(2)出现下面错误

"_CVPixelBufferGetBaseAddress", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_CVPixelBufferUnlockBaseAddress", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_CVPixelBufferLockBaseAddress", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_CMSampleBufferGetImageBuffer", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_CVPixelBufferGetHeight", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_kCVPixelBufferPixelFormatTypeKey", referenced from:
      _kCVPixelBufferPixelFormatTypeKey$non_lazy_ptr in MainViewController.o
     (maybe you meant: _kCVPixelBufferPixelFormatTypeKey$non_lazy_ptr)
  "_CVPixelBufferGetWidth", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_CVPixelBufferGetBytesPerRow", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o
  "_CMTimeMake", referenced from:
      -[MainViewController setupCaptureSession] in MainViewController.o
  "_CVPixelBufferGetDataSize", referenced from:
      -[MainViewController imageFromSampleBuffer:] in MainViewController.o

解决方法是添加 AVFoundation , CoreVideo 和 CoreMedia frameworks 

(3)出现下面错误assert错误时，需要添加AssetsLibrary.framework