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UIView+MGBadgeView.h

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+//
+//  UIView+MGBadgeView.h
+//  purl
+//
+//  Created by Matteo Gobbi on 28/05/2014.
+//  Copyright (c) 2014 Matteo Gobbi (Voxygen). All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+
+
+typedef NS_ENUM(NSUInteger, MGBadgePosition) {
+    MGBadgePositionTopLeft,
+    MGBadgePositionTopRight,
+    MGBadgePositionBottomLeft,
+    MGBadgePositionBottomRight,
+    MGBadgePositionBest
+};
+
+
+@interface MGBadgeView : UIView
+
+@property (nonatomic) MGBadgePosition position;
+
+@property (nonatomic) NSInteger badgeValue;
+
+@property(strong, nonatomic) UIFont *font;
+
+@property(strong, nonatomic) UIColor *badgeColor;
+
+@property(strong, nonatomic) UIColor *textColor;
+
+@property(strong, nonatomic) UIColor *outlineColor;
+
+@property (nonatomic) float outlineWidth;
+
+@property (nonatomic) float minDiameter;
+
+@property (nonatomic) BOOL displayIfZero;
+
+@end
+
+
+@interface UIView (MGBadgeView)
+
+@property(nonatomic, readonly) MGBadgeView *badgeView;
+
+@end

UIView+MGBadgeView.m

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+//
+//  UIView+MGBadgeView.m
+//  purl
+//
+//  Created by Matteo Gobbi on 28/05/2014.
+//  Copyright (c) 2014 Matteo Gobbi (Voxygen). All rights reserved.
+//
+
+#import "UIView+MGBadgeView.h"
+#import <objc/runtime.h>
+
+@implementation MGBadgeView
+
+static float const kMGBadgeViewInnerSpaceFromBorder = 7.0;
+static int const kMGBadgeViewTag = 9876;
+
+#define BADGE_SIDE_OFFSET kMGBadgeViewInnerSpaceFromBorder + _outlineWidth
+#define BADGE_TOTAL_OFFSET BADGE_SIDE_OFFSET * 2.0
+
+- (instancetype)initWithFrame:(CGRect)frame {
+
+    if(self = [super initWithFrame:frame]) {
+
+        _font = [UIFont boldSystemFontOfSize:13.0];
+        _badgeColor = [UIColor blueColor];
+        _textColor = [UIColor whiteColor];
+        _outlineColor = [UIColor whiteColor];
+        _outlineWidth = 2.0;
+        _minDiameter = 25.0;
+        _position = MGBadgePositionBest;
+        _displayIfZero = NO;
+
+        self.backgroundColor = [UIColor clearColor];
+        self.opaque = YES;
+        self.tag = kMGBadgeViewTag;
+
+    }
+
+    return self;
+}
+
+- (void)drawRect:(CGRect)rect {
+
+    if(_badgeValue != 0 || _displayIfZero) {
+
+        NSString *stringToDraw = [NSString stringWithFormat:@"%ld", (long)_badgeValue];
+
+        CGContextRef context = UIGraphicsGetCurrentContext();
+
+        [_outlineColor set];
+        CGContextFillEllipseInRect(context, CGRectInset(rect, 1.0, 1.0));
+
+        [_badgeColor set];
+        CGContextFillEllipseInRect(context, CGRectInset(rect, _outlineWidth + 1.0, _outlineWidth + 1.0));
+
+        CGSize numberSize = [stringToDraw sizeWithAttributes:@{NSFontAttributeName: _font}];
+
+        [_textColor set];
+        NSMutableParagraphStyle *paragrapStyle = [NSMutableParagraphStyle new];
+        paragrapStyle.lineBreakMode = NSLineBreakByClipping;
+        paragrapStyle.alignment = NSTextAlignmentCenter;
+
+        CGRect lblRect = CGRectMake(rect.origin.x, (rect.size.height / 2.0) - (numberSize.height / 2.0), rect.size.width, numberSize.height);
+
+        [stringToDraw drawInRect:lblRect withAttributes:@{
+                                                          NSFontAttributeName : _font,
+                                                          NSParagraphStyleAttributeName : paragrapStyle,
+                                                          NSForegroundColorAttributeName : _textColor
+                                                          }];
+
+    }
+}
+
+#pragma mark - Properties accessor methods
+
+- (void)setBadgeValue:(NSInteger)badgeValue {
+
+    if(_badgeValue != badgeValue) {
+
+        _badgeValue = badgeValue;
+
+        if(badgeValue != 0 || _displayIfZero) {
+            [self mg_updateBadgeViewSize];
+
+            if(_position == MGBadgePositionBest)
+                [self mg_updateBadgeViewPosition];
+
+        } else {
+            self.frame = CGRectZero;
+        }
+
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setPosition:(MGBadgePosition)position {
+    if(_position != position) {
+        _position = position;
+        [self mg_updateBadgeViewPosition];
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setMinDiameter:(float)minDiameter {
+    if (_minDiameter != minDiameter) {
+        _minDiameter = minDiameter;
+
+        if(_position == MGBadgePositionBest)
+            [self mg_updateBadgeViewPosition];
+
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setBadgeColor:(UIColor *)badgeColor {
+    if(_badgeColor != badgeColor) {
+        _badgeColor = badgeColor;
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setTextColor:(UIColor *)textColor {
+    if(_textColor != textColor) {
+        _textColor = textColor;
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setOutlineColor:(UIColor *)outlineColor {
+    if(_outlineColor != outlineColor) {
+        _outlineColor = outlineColor;
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setOutlineWidth:(float)outlineWidth {
+    if(_outlineWidth != outlineWidth) {
+        _outlineWidth = outlineWidth;
+
+        if(_position == MGBadgePositionBest)
+            [self mg_updateBadgeViewPosition];
+
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setFont:(UIFont *)font {
+    if(_font != font) {
+        _font = font;
+
+        [self mg_updateBadgeViewSize];
+
+        if(_position == MGBadgePositionBest)
+            [self mg_updateBadgeViewPosition];
+
+
+        [self setNeedsDisplay];
+    }
+}
+
+- (void)setDisplayIfZero:(BOOL)displayIfZero {
+    if(_displayIfZero != displayIfZero) {
+        _displayIfZero = displayIfZero;
+
+        if(_badgeValue == 0) {
+            if(_displayIfZero) {
+                [self mg_updateBadgeViewSize];
+
+                if(_position == MGBadgePositionBest)
+                    [self mg_updateBadgeViewPosition];
+            } else {
+                self.frame = CGRectZero;
+            }
+        }
+    }
+}
+
+#pragma mark - Private methods
+
+- (void)mg_updateBadgeViewSize {
+    //Calculate badge bounds
+    CGSize numberSize = [[NSString stringWithFormat:@"%ld", (long)_badgeValue] sizeWithAttributes:@{NSFontAttributeName: _font}];
+
+    float badgeHeight = MAX(BADGE_TOTAL_OFFSET + numberSize.height, _minDiameter);
+    float badgeWidth = MAX(badgeHeight, BADGE_TOTAL_OFFSET + numberSize.width);
+
+    [self setBounds:CGRectMake(0, 0, badgeWidth, badgeHeight)];
+}
+
+
+- (void)mg_updateBadgeViewPosition {
+    CGRect superviewFrame = self.superview.frame;
+    CGSize badgeSize = self.bounds.size;
+
+    MGBadgePosition position = _position;
+
+    //Set the best position before
+    if(position == MGBadgePositionBest) {
+        CGPoint topRightInWindow = [self.superview convertPoint:CGPointMake(superviewFrame.origin.x + superviewFrame.size.width + (badgeSize.width / 2.0), -(badgeSize.height / 2.0)) fromView:nil];
+
+        CGSize appFrameSize = [[UIScreen mainScreen] applicationFrame].size;
+
+        if(topRightInWindow.x > appFrameSize.width) {
+            position = (topRightInWindow.y < appFrameSize.height) ? MGBadgePositionBottomLeft : MGBadgePositionTopLeft;
+        } else {
+            position = (topRightInWindow.y < appFrameSize.height) ? MGBadgePositionBottomRight : MGBadgePositionTopRight;
+        }
+    }
+
+    switch (position) {
+        case MGBadgePositionTopRight: {
+            self.center = CGPointMake(superviewFrame.size.width, 0);
+            break;
+        }
+        case MGBadgePositionTopLeft: {
+            self.center = CGPointMake(0, 0);
+            break;
+        }
+        case MGBadgePositionBottomRight: {
+            self.center = CGPointMake(superviewFrame.size.width, superviewFrame.size.height);
+            break;
+        }
+        case MGBadgePositionBottomLeft: {
+            self.center = CGPointMake(0, superviewFrame.size.height);
+            break;
+        }
+        default:
+            break;
+    }
+}
+
+@end
+
+
+
+static const char *kMGBadgeViewPropertyKey = "kMGBadgeViewPropertyKey";
+
+@implementation UIView (MGBadgeView)
+
+- (void)setBadgeView:(MGBadgeView *)badgeView {
+    objc_setAssociatedObject(self, kMGBadgeViewPropertyKey, badgeView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+}
+
+- (MGBadgeView *)badgeView {
+
+    MGBadgeView *badgeView = objc_getAssociatedObject(self, kMGBadgeViewPropertyKey);
+
+    if (!badgeView) {
+        self.badgeView = [[MGBadgeView alloc] initWithFrame:CGRectZero];
+        badgeView = objc_getAssociatedObject(self, kMGBadgeViewPropertyKey);
+        [self addSubview:badgeView];
+    }
+
+    return badgeView;
+}
+
+@end
+
+