CODEWITHSUNDEEP
c++iosobjective-cxcodeopencv
mm24
mm24

Reputation: 9596

Xcode 7 and openCV (no Swift): Core.hpp header must be compiled as C++

I have followed the instructions on how to install OpenCV on an iOS project. However when using Xcode 7 I had to add manually a prefix header. Doing this unfortunately did not help and I was still getting compile errors. I then read another post suggesting that is best to add manually the imports and not use prefix headers in Xcode 7, so I did.

Here is my code:

#import "ViewController.h"

#import <opencv2/opencv.hpp>
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import <opencv2/highgui/cap_ios.h>
//using namespace cv;

@interface ViewController ()
{
    IBOutlet UIImageView* imageView;
    IBOutlet UIButton* button;
}

- (IBAction)actionStart:(id)sender;

@end

However I still get the following errors.

enter image description here enter image description here

When I uncomment the using namespace cv; I get the following:

enter image description here

I found some complex solutions talking about exposing headers to Swift etc.. I just want my project to work on Objective-C with Xcode 7 ...

Upvotes: 20

Views: 13063

Answers (4)

Ostoura
Ostoura

Reputation: 2543

The solution is almost the same as we do bridging ObjectiveC and swift but we do it between Objective C and C++ so we put the C++ codes in a separate file with (.mm) extension and then import it to your Objective C File (.m)

For example if you have ViewController.h and ViewController.m you add two more files which include your C++ codes lets name it OpenCV.mm and OpenCV.h then import the OpenCV.h inside ViewController.m even before you import anything else. May be this image will help understand it: enter image description here

Tested on Xcode 11.6 OpenCV Ver 3.4.3

Upvotes: 3

Jimmy
Jimmy

Reputation: 56

Try placing #import < opencv2/opencv.hpp > before #import "ViewController.h".Source

Upvotes: 1

bRo
bRo

Reputation: 446

I just had the exact same problem. I'm working in a Swift project with OpenCV.

Regarding Swift, its entry point to OpenCV is a file I called OpenCVWrapper. So I got OpenCVWrapper.h and OpenCVWrapper.mm. In the bridging header of my project, I got #import "OpenCVWrapper.h".

Thing is I wanted to write a class called MatUtils in Objective-C++ that I could call from OpenCVWrapper.mm. For them to be seeable in there, I had to put them in MatUtils.h.

Long story short, the mistake is that in OpenCVWrapper.h, I did #import "MatUtils.h". MISTAKE!!!! As OpenCVWrapper is in the bridging header, C++ is now reachable from Swift!

Quick fix : #import "MatUtils.h" in OpenCVWrapper.mm!

Cheers! bRo

Upvotes: 16

Anya Shenanigans
Anya Shenanigans

Reputation: 94654

OpenCV is a C++ framework, which means that any code that makes use of OpenCV has to be compiled with C++ interpretation, rather than C interpretation.

The errors you see, e.g. with the using namespace cv; indicate that the code is compiled using the objective-C compiler, rather than the objective-C++ compiler.

As I mentioned in my comment the easiest way to get this to happen is to ensure that any file that #includes an opencv header must be named e.g. ViewController.mm, i.e. it must be an Objective-C++ file.

Alternatively, you can select and override the Type of the file, by explicitly selecting the Objective-C++ Source option for the file type in the utilities pane. utilities pane drop-down selection

Upvotes: 31

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