implemented method getFOV for ios

ios/RCTCameraManager.m

@@ -232,16 +232,48 @@ RCT_EXPORT_METHOD(stopCapture) {
   }
 }
 
+RCT_EXPORT_METHOD(getFOV: (RCTResponseSenderBlock)callback) {
+  NSArray *devices = [AVCaptureDevice devices];
+  AVCaptureDevice *frontCamera;
+  AVCaptureDevice *backCamera;
+  double frontFov;
+  double backFov;
+
+  for (AVCaptureDevice *device in devices) {
+
+      NSLog(@"Device name: %@", [device localizedName]);
+
+      if ([device hasMediaType:AVMediaTypeVideo]) {
+
+          if ([device position] == AVCaptureDevicePositionBack) {
+              NSLog(@"Device position : back");
+              backCamera = device;
+              backFov = backCamera.activeFormat.videoFieldOfView;
+          }
+          else {
+              NSLog(@"Device position : front");
+              frontCamera = device;
+              frontFov = frontCamera.activeFormat.videoFieldOfView;
+          }
+      }
+  }
+
+  callback(@[[NSNull null], @{
+    @"backCamera": [NSNumber numberWithDouble: backFov],
+    @"frontCamera": [NSNumber numberWithDouble: frontFov]
+  }]);
+}
+
 - (void)startSession {
 #if TARGET_IPHONE_SIMULATOR
   return;
 #endif
-	
+
   dispatch_async(self.sessionQueue, ^{
     if (self.presetCamera == AVCaptureDevicePositionUnspecified) {
       self.presetCamera = AVCaptureDevicePositionBack;
     }
-    
+
     AVCaptureStillImageOutput *stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
     if ([self.session canAddOutput:stillImageOutput])
     {
@@ -249,14 +281,14 @@ RCT_EXPORT_METHOD(stopCapture) {
       [self.session addOutput:stillImageOutput];
       self.stillImageOutput = stillImageOutput;
     }
-    
+
     AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
     if ([self.session canAddOutput:movieFileOutput])
     {
       [self.session addOutput:movieFileOutput];
       self.movieFileOutput = movieFileOutput;
     }
-    
+
     AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
     if ([self.session canAddOutput:metadataOutput]) {
       [metadataOutput setMetadataObjectsDelegate:self queue:self.sessionQueue];
@@ -264,7 +296,7 @@ RCT_EXPORT_METHOD(stopCapture) {
       [metadataOutput setMetadataObjectTypes:metadataOutput.availableMetadataObjectTypes];
       self.metadataOutput = metadataOutput;
     }
-    
+
     __weak RCTCameraManager *weakSelf = self;
     [self setRuntimeErrorHandlingObserver:[NSNotificationCenter.defaultCenter addObserverForName:AVCaptureSessionRuntimeErrorNotification object:self.session queue:nil usingBlock:^(NSNotification *note) {
       RCTCameraManager *strongSelf = weakSelf;
@@ -273,7 +305,7 @@ RCT_EXPORT_METHOD(stopCapture) {
         [strongSelf.session startRunning];
       });
     }]];
-    
+
     [self.session startRunning];
   });
 }
@@ -282,7 +314,7 @@ RCT_EXPORT_METHOD(stopCapture) {
 #if TARGET_IPHONE_SIMULATOR
   return;
 #endif
-	
+
   dispatch_async(self.sessionQueue, ^{
     self.camera = nil;
     [self.previewLayer removeFromSuperlayer];
@@ -290,7 +322,7 @@ RCT_EXPORT_METHOD(stopCapture) {
     for(AVCaptureInput *input in self.session.inputs) {
       [self.session removeInput:input];
     }
-    
+
     for(AVCaptureOutput *output in self.session.outputs) {
       [self.session removeOutput:output];
     }
@@ -299,19 +331,19 @@ RCT_EXPORT_METHOD(stopCapture) {
 
 - (void)initializeCaptureSessionInput:(NSString *)type {
   dispatch_async(self.sessionQueue, ^{
-    
+
     [self.session beginConfiguration];
-    
+
     NSError *error = nil;
     AVCaptureDevice *captureDevice;
-    
+
     if (type == AVMediaTypeAudio) {
       captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
     }
     else if (type == AVMediaTypeVideo) {
       captureDevice = [self deviceWithMediaType:AVMediaTypeVideo preferringPosition:self.presetCamera];
     }
-    
+
     if (captureDevice == nil) {
       return;
     }