I need to use a library in my C++ project that needs to call an extern function:
SetGameViewController(UIViewController* gameViewController)
I have zero knowledge of Objective C and iOS yet. I need to get UIViewController and pass it to that function.
So this code should get the UIViewController:
UIWindow *window = [UIApplication sharedApplication].keyWindow;
UIViewController *rootViewController = window.rootViewController;
I also added this import:
#if defined(OS_IPHONE)
#import <UIKit/UIKit.h>
#endif
I get compiler errors like:
Expected unqualified-id
Unknown type name 'NSString'
I've started learning Objective C and read a few articles but couldn't get much further than that yet.
So basically my question is how do I basically import and use Objective C code in C++ code so that I can get and use the UIViewController?
Easiest way will be to rename your source file with the extension ".mm" - it will then be compiled as objective-c++, which means you get all the wonders of c++ while still being able to interact with objective-c objects (counted pointers to things 'derived' from NSObject).
Related
I'm trying to implement biometric authentication on iOS from a C++ codebase. Here is one example.
In order to achieve this, I need to use the LAContext obj-c APIs. However, when I try to initialize the class from C++ I get a pointer/reference error:
// Cannot initialize a variable of type 'LAContext *__strong' with an rvalue of type 'LAContext'
LAContext* authContext = LAContext();
Is there any way to achieve this? Or is this struct available from Obj-c only?
Edit 1:
My file is in Obj-C++, so in theory I should be able to mix C++ and Obj-C code, however when I try to write a Obj-C function to alloc the LAContext object I get a missing symbols error:
-(bool)biometricsAvailable {
LAContext *myContext = [[LAContext alloc] init];
NSError *authError = nil;
return true;
}
On the compilation step this error is thrown:
Undefined symbol: _OBJC_CLASS_$_LAContext
XCode itself does not show any error while editing the file, only happens when I try to build/compile the app.
As it turns out, the problem was not with mixing C++ and Obj-C code, but rather with my library being linked via cocoapods and the LocalAuthentication framework being missing.
I needed to add:
s.frameworks = "LocalAuthentication"
to the podspec and creating a LAContext instance works just fine.
I'm a beginner with Xcode...
I'm trying to use openCV c++ with Scenekit=> to make an AR scene.
Well, I was too optimistic.
1/I started to use the default XCode template for game.=> works!
2/openCV without scenekit=> works
3/ mixing...
I imported some c++ headers in the gameviewController file (basically a UIViewController with scenekit inside).
If I let it so, I get compiler error (cstddef not defined). Fair enough, it's C++ so, from what I read, I just have to rename .m to .mm
But, in this case, I get a full list of linker errors such as Undefined symbols for architecture arm64:
"_OBJC_CLASS_$_SCNAction", referenced from:
=> I guess it is more tricky to mix objective C and C++ but on a simpler project, without Scenekit but with a very similar code otherwise, it worked nicely.
Any clue or guide for mixing them? Should I use swift?
Thanks a lot,
Michael
I just need to add "SceneKit.framework" to Link Binary With Libraries:
Same problem here. I had a pure Objective-C class, simply named "GameViewController.m". To turn it into an Obj-C++ class, change the ".m" to ".mm".
However, just by changing the extension, the linker spat back 13 undefined symbols....
"_OBJC_CLASS_$_SCNTransaction", referenced from: ...
"_OBJC_CLASS_$_SCNFloor", referenced from: ...
"_OBJC_CLASS_$_SCNMaterial", referenced from: ...
etc...
To get around this, just create a different (new) Obj-C++ class, with a .mm extension, and place your C++ code in that class.
Now you can instantiate that new class from the class containing SceneKit calls and call the methods in the new Obj-C++ class.
Inside the GameViewcontroller.m class:
...
scene = [SCNScene sceneNamed:#"art.scnassets/grid.dae"];
kinematics = [[KinematicScene alloc] init];
[kinematics setupCharacters];
...
And inside the new Obj-C++ class (KinematicsScene.mm)
#implementation KinematicScene
{
AI::Location *location;
}
-(id) init
{
self = [super init];
if( self )
{
AI::KinematicSeek* seek = new AI::KinematicSeek[2];
location = new AI::Location[2];
}
return self;
}
-(void) setupCharacters
{
.....
}
... etc ....
#end
This worked for me:
Disable module support [CLANG_ENABLE_MODULES, -fmodules]. This has user experience downsides. Read the online help for this setting before disabling it, and also be aware that if you disable it you will become responsible for hunting down the libraries and frameworks you need to link against, and this can be tedious if you are not an old hand.
Build and (attempt to) link. Add the frameworks and libraries you need to resolve the link errors. I recommend creating a group in your project and directing it to your SDK, then adding the frameworks and libraries relative to that SDK.
I'm trying to intercept some native library-calls via LD_PRELOAD.
This is working fine for simple libraries written in C, but now I try to go further and override some more complex class-methods from the AOSP written in C++.
Here's my example:
#include <rs/cpp/util/RefBase.h>
namespace android {
sp<MediaCodec> MediaCodec::CreateByType(const sp<ALooper> &looper, const char *mime, bool encoder) {
// TODO this will be implemented by me
return NULL;
}
}
In my Application.mk, I got the following piece of code:
APP_STL := gnustl_static
and inside the Android.mk this one:
LOCAL_STATIC_LIBRARIES += libstlport_static
Sadly, the error I get is the following:
jni/libhook/ld_preload.cpp:88:1: error: 'sp' does not name a type
Anyone an idea how to use sp<..> here? I assume it's not Android-specific but a standard C++-thing - I'm totally new at C++, just started "today" :)
I know this may be bad practice, so I'm welcome for any other idea.
sp<> is Android-specific. sp<> is Strong Pointer, wp<> is Weak Pointer; they came into being as part of the Binder IPC implementation.
The place to start looking for the implementation is the framework RefBase.h, which is a bit twisty for a C++ newcomer. None of what you're fiddling with is part of the public API defined by the NDK, which means it's subject to change between releases, so be aware that what you're trying to do may not work across devices or software updates.
So I've followed the steps mentioned here: http://zxing.googlecode.com/svn/trunk/iphone/README
And I made sure everything is alright but yet my QRCodeReader isn't being recognized in myVC.mm file.
This is what's the situation:
The project is put into my own project as described in the link.
I've imported the #import "ZXingWidgetController.h" in the header file and it is being recognized.
I've imported the #import "QRCodeReader.h" in the implementation file (.mm)
Then I alloced them both in a targetmethod of some button like this:
ZXingWidgetController *widController = [[ZXingWidgetController alloc] initWithDelegate:self showCancel:YES OneDMode:NO];
widController.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:#"qr_code_initialising_bg.png"]];
QRCodeReader* qrcodeReader = [[QRCodeReader alloc] init];
NSSet *readers = [[NSSet alloc ] initWithObjects:qrcodeReader,nil];
[qrcodeReader release];
widController.readers = readers;
[readers release];
[self presentModalViewController:widController animated:YES];
Now it tells me that this is the problem:
QRCodeReader* qrcodeReader = [[QRCodeReader alloc] init];
NSSet *readers = [[NSSet alloc ] initWithObjects:qrcodeReader,nil];
[qrcodeReader release];
It says: Use of undeclared identifier 'QRCodeReader'
Why does it not see my import of the QRCodeReader in the seem .mm
file?
What did I forget that is not in the description that I used?
And most important, how do I fix this to recognize the QRCodeReader?
The straight C++ code (not Objective C++) uses C++ namespaces.
You need to either say zxing::qrcode::QRCodeReader or use using statements like
using namespace zxing;
using namespace zxing::qrcode;
Update:
The code above does bring in the C++ class but there's actually a widget class of the same name which I forgot about. It is an Objective C class that wraps the C++ class and is what you want. Instead of the code above, just #import "QRCodeReader.h" ... which you said you did. I expect the two files of the same name are colliding. Did you set the "recursive" option when including the cpp files? The README says "don't need to" but should probably say "must not". That could cause the cpp file to be included and not the widget version.
I had this exact same problem at the end the solution was kind of easy.
I put the .mm file with "Location" -> "Relative to Project".
Hope this help
To cut a long story short, my project (an iPhone app) was all working fine until I started using a C++ sdk (openfeint). Everything was working fine, including the C+++ Openfeint stuff, until I switched from tesitng on the device to testing in the simulator.
Now it won't compile for anything and I'm getting just under 200 errors. It's all just spiralled out of control and wont compile on any device. As I said, everything was working perfectly, I didn't change a single line of code, I simply switched Active SDK's.
So I'll start at the beginning. The first error is...
Error 1: ISO C++ forbids of declaration 'BrickControlLayer' with no type
Clicking on this error takes me to the header file for another class...
// GameScene.h
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#import "brickSprite.h"
#import "BrickControlLayer.h"
#import "GameState.h"
#import "ScoreController.h"
#import "FeedbackLayer.h"
#import "TimeBar.h"
#interface GameScene : Layer {
GameState *gameState;
ScoreController *scoreController;
CocosNode *spriteHolder;
brickSprite *targetBrick;
// Heres the line it takes me too <<<<<<<<<<<<<<<<<
BrickControlLayer *controls;
NSInteger difficulty;
NSMutableArray *pointsLookupArray;
BitmapFontAtlas *scoreLabel;
FeedbackLayer *feedback;
NSDate *startTime;
TimeBar *timeProgress;
int rowScanCount, foundRows;
}
// methods here....
#end
I'm new to this, so bear with me. I was confused as I'm clearly stating that *controls is of the type 'BrickControlLayer'. So I'm thinking there's something wrong inside 'BrickControlLayer' itself.
Here's the header...
// BrickControlLayer.h
#import <Foundation/Foundation.h>
#import "cocos2d.h"
#import "brickSprite.h"
#import "HighScores.h"
#interface BrickControlLayer : Layer{
CocosNode *spriteHolder;
CGPoint touchedStartPoint, moveFromPoint;
brickSprite *touchedBrick;
BOOL editorMode;
int movecount;
// Control buttons
AtlasSpriteManager *buttonManager;
AtlasSprite *rotLeft, *rotRight, *newBrick, *deleteBrick, *makeTarget, *save, *run;
BOOL tapToContinue;
}
#property (retain, readwrite) CocosNode *spriteHolder;
#property (retain, readwrite) brickSprite *touchedBrick;
-(void)showEditorControls;
-(void)selectBrickAtLocation:(CGPoint)location;
-(void)hideEditorControls;
-(void)deactivate;
#end
I've been over it and over it. It was all working fine before and I simply can't figure it out. I've been googling it and the only thing that crops up is the term "Forward Declaration", but that doesn't mean anything to me and all the info I've found talks about structs.
I suspect the errors are more of an indication that I'm doing lot's of other things wrong, rather than committing a simple one line typo or something. Can anyone explain in laymans terms what's going on here?
Jason here from OpenFeint. If you'd like to send over a code sample to devsupport at openfeint dot com that demonstrates the problem we'll take a look at it for you. It sounds like you may be including the header file from a .CPP instead of a .MM file.
If all you did was change the iPhone Target SDK, double check that when you setup compiler options you did it for all SDKs and build configurations (release, debug).
The error you're getting sounds like the compiler doesn't recognize that you're in an Objective-C declaration OR it can't find the header declaration for BrickControlLayer. Could be a circular include? (do you use include guards or #pragma once?)
Hope that helps,
- Jason Citron
- Founder & CEO, Aurora Feint
Your error is about BrickController not BrickControlLayer so I don't think that you've posted the line that the compiler is actually complaining about.
Having said that, I think that your fundamental problem is that you are trying to compile files that look to be Objective C with something that, from it's error messages, thinks that it is an ISO C++ compiler.
Have you followed all of the steps listed on the Integrating the OpenFeint SDK page?
Alternatively, you could create one single class that is Objective-C++ that interfaces with OpenFeint. Then all your Objective-C classes can remain the same but make calls to the OpenFeint handler class.
Have you renamed all files that include or import OpenFeint to .mm ? Also have you tried turning off (or on) 'compile for thumb' in your build settings?