add centerCircleBackgroundColor property

Sources/ObjectiveChart/Charts/PieChart/Controller/PieChartController.h

@@ -15,6 +15,7 @@
 
 /*! @brief Value that controls the thickness of pieces in the pie chart*/
 @property CGFloat centerCircleRadius;
+@property UIColor* centerCircleBackgroundColor;
 
 @end
 

Sources/ObjectiveChart/Charts/PieChart/Controller/PieChartController.m

@@ -14,10 +14,20 @@ @implementation PieChartController
 @synthesize backgroundView;
 @synthesize database;
 @synthesize centerCircleRadius;
+@synthesize centerCircleBackgroundColor;
 
 //Delegate
 @synthesize radius;
 
+- (instancetype)init
+{
+    self = [super init];
+    if (self) {
+        centerCircleBackgroundColor = [UIColor blackColor];
+    }
+    return self;
+}
+
 - (void)layoutSubviews {
     [super layoutSubviews];
 
@@ -44,7 +54,7 @@ - (void)layoutSubviews {
     }
 
     UIView *centerCircleView = [[UIView alloc] init];
-    centerCircleView.backgroundColor = [UIColor blackColor];
+    centerCircleView.backgroundColor = centerCircleBackgroundColor;
     centerCircleView.layer.cornerRadius = centerCircleRadius/2;
     centerCircleView.translatesAutoresizingMaskIntoConstraints = NO;
     [self addSubview: centerCircleView];