# Revision history [back]

1. first follow this to create prefix file (YourPrefixFileName.pch)

#ifdef __cplusplus
#import <opencv2/opencv.hpp>
#endif

#ifndef YourProjectName_YourPrefixFileName_pch
#define YourProjectName_YourPrefixFileName_pch

// Include any system framework and library headers here that should be included in all compilation units.
// You will also need to set the Prefix Header build setting of one or more of your targets to reference this file.

#endif

3. rename your ViewController's extension from .m (ViewController.m) to .mm (ViewController.mm)