app内部角标的需求可以说是随处可见，今天就写了一个Button的角标类，方便以后调用，此处做记录使用，有需要的旁友，可以直接copy后食用。
废话不多说，直接上代码。

//
//  UIButton+Badge.h
//  buttonBadge
//
//  Created by wuwj on 16/6/20.
//  Copyright © 2016年 wuwj. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIButton (Badge)

@property (strong, nonatomic) UILabel *badge;

/**
 *  角标显示的信息，可以为数字和文字
 */
@property (nonatomic) NSString *badgeValue;
/**
 *  角标背景颜色，默认为红色
 */
@property (nonatomic) UIColor *badgeBGColor;
/**
 *  角标文字的颜色
 */
@property (nonatomic) UIColor *badgeTextColor;
/**
 *  角标字号
 */
@property (nonatomic) UIFont *badgeFont;
/**
 *  角标的气泡边界
 */
@property (nonatomic) CGFloat badgePadding;
/**
 *  角标的最小尺寸
 */
@property (nonatomic) CGFloat badgeMinSize;
/**
 *  角标的x值
 */
@property (nonatomic) CGFloat badgeOriginX;
/**
 *  角标的y值
 */
@property (nonatomic) CGFloat badgeOriginY;
/**
 *  当角标为0时，自动去除角标
 */
@property BOOL shouldHideBadgeAtZero;
/**
 *  当角标的值发生变化，角标的动画是否显示
 */
@property BOOL shouldAnimateBadge;

@end

//
//  UIButton+Badge.m
//  buttonBadge
//
//  Created by wuwj on 16/6/20.
//  Copyright © 2016年 wuwj. All rights reserved.
//

#import "UIButton+Badge.h"
#import <objc/runtime.h>

NSString const *badgeKey                 = @"badgeKey";

NSString const *badgeBGColorKey          = @"badgeBGColorKey";
NSString const *badgeTextColorKey        = @"badgeTextColorKey";
NSString const *badgeFontKey             = @"badgeFontKey";
NSString const *badgePaddingKey          = @"badgePaddingKey";
NSString const *badgeMinSizeKey          = @"badgeMinSizeKey";
NSString const *badgeOriginXKey          = @"badgeOriginXKey";
NSString const *badgeOriginYKey          = @"badgeOriginYKey";
NSString const *shouldHideBadgeAtZeroKey = @"shouldHideBadgeAtZeroKey";
NSString const *shouldAnimateBadgeKey    = @"shouldAnimateBadgeKey";
NSString const *badgeValueKey            = @"badgeValueKey";

@implementation UIButton (Badge)

- (void)badgeInit
{
    // 初始化，设定默认值
    self.badgeBGColor   = [UIColor redColor];
    self.badgeTextColor = [UIColor whiteColor];
    self.badgeFont      = [UIFont systemFontOfSize:12.0];
    self.badgePadding   = 6;
    self.badgeMinSize   = 8;
    self.badgeOriginX   = self.frame.size.width - self.badge.frame.size.width/2;
    self.badgeOriginY   = -4;
    self.shouldHideBadgeAtZero = YES;
    self.shouldAnimateBadge = YES;
    // 避免角标被裁剪
    self.clipsToBounds = NO;
}

#pragma mark - Utility methods

// 当角标的属性改变时，调用此方法
- (void)refreshBadge
{
    // 更新属性
    self.badge.textColor        = self.badgeTextColor;
    self.badge.backgroundColor  = self.badgeBGColor;
    self.badge.font             = self.badgeFont;
}

- (CGSize) badgeExpectedSize
{
    // 自适应角标
    UILabel *frameLabel = [self duplicateLabel:self.badge];
    [frameLabel sizeToFit];
    
    CGSize expectedLabelSize = frameLabel.frame.size;
    return expectedLabelSize;
}
/**
 *  更新角标的frame
 */
- (void)updateBadgeFrame
{
    
    CGSize expectedLabelSize = [self badgeExpectedSize];
    
    CGFloat minHeight = expectedLabelSize.height;
    
    // 判断如果小于最小size，则为最小size
    minHeight = (minHeight < self.badgeMinSize) ? self.badgeMinSize : expectedLabelSize.height;
    CGFloat minWidth = expectedLabelSize.width;
    CGFloat padding = self.badgePadding;
    
    // 填充边界
    minWidth = (minWidth < minHeight) ? minHeight : expectedLabelSize.width;
    self.badge.frame = CGRectMake(self.badgeOriginX, self.badgeOriginY, minWidth + padding, minHeight + padding);
    self.badge.layer.cornerRadius = (minHeight + padding) / 2;
    self.badge.layer.masksToBounds = YES;
}

// 角标值变化
- (void)updateBadgeValueAnimated:(BOOL)animated
{
    // 动画效果
    if (animated && self.shouldAnimateBadge && ![self.badge.text isEqualToString:self.badgeValue]) {
        CABasicAnimation * animation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
        [animation setFromValue:[NSNumber numberWithFloat:1.5]];
        [animation setToValue:[NSNumber numberWithFloat:1]];
        [animation setDuration:0.2];
        [animation setTimingFunction:[CAMediaTimingFunction functionWithControlPoints:.4f :1.3f :1.f :1.f]];
        [self.badge.layer addAnimation:animation forKey:@"bounceAnimation"];
    }
    self.badge.text = self.badgeValue;
    
    // 动画时间
    NSTimeInterval duration = animated ? 0.2 : 0;
    [UIView animateWithDuration:duration animations:^{
        [self updateBadgeFrame];
    }];
}

- (UILabel *)duplicateLabel:(UILabel *)labelToCopy
{
    UILabel *duplicateLabel = [[UILabel alloc] initWithFrame:labelToCopy.frame];
    duplicateLabel.text = labelToCopy.text;
    duplicateLabel.font = labelToCopy.font;
    
    return duplicateLabel;
}

- (void)removeBadge
{
    // 移除角标
    [UIView animateWithDuration:0.2 animations:^{
        self.badge.transform = CGAffineTransformMakeScale(0, 0);
    } completion:^(BOOL finished) {
        [self.badge removeFromSuperview];
        self.badge = nil;
    }];
}

#pragma mark - getters/setters
-(UILabel*) badge {
    return objc_getAssociatedObject(self, &badgeKey);
}
-(void)setBadge:(UILabel *)badgeLabel
{
    objc_setAssociatedObject(self, &badgeKey, badgeLabel, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

// 显示角标
-(NSString *)badgeValue {
    return objc_getAssociatedObject(self, &badgeValueKey);
}

-(void) setBadgeValue:(NSString *)badgeValue
{
    objc_setAssociatedObject(self, &badgeValueKey, badgeValue, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    
    // 当角标信息不存在，或者为空，则移除
    if (!badgeValue || [badgeValue isEqualToString:@""] || ([badgeValue isEqualToString:@"0"] && self.shouldHideBadgeAtZero)) {
        [self removeBadge];
    } else if (!self.badge) {
        //当又有值时，重新设置角标
        self.badge                      = [[UILabel alloc] initWithFrame:CGRectMake(self.badgeOriginX, self.badgeOriginY, 20, 20)];
        self.badge.textColor            = self.badgeTextColor;
        self.badge.backgroundColor      = self.badgeBGColor;
        self.badge.font                 = self.badgeFont;
        self.badge.textAlignment        = NSTextAlignmentCenter;
        [self badgeInit];
        [self addSubview:self.badge];
        [self updateBadgeValueAnimated:NO];
    } else {
        [self updateBadgeValueAnimated:YES];
    }
}

//进行关联
-(UIColor *)badgeBGColor {
    return objc_getAssociatedObject(self, &badgeBGColorKey);
}
//获取关联
-(void)setBadgeBGColor:(UIColor *)badgeBGColor
{
    objc_setAssociatedObject(self, &badgeBGColorKey, badgeBGColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self refreshBadge];
    }
}

-(UIColor *)badgeTextColor {
    return objc_getAssociatedObject(self, &badgeTextColorKey);
}
-(void)setBadgeTextColor:(UIColor *)badgeTextColor
{
    objc_setAssociatedObject(self, &badgeTextColorKey, badgeTextColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self refreshBadge];
    }
}

-(UIFont *)badgeFont {
    return objc_getAssociatedObject(self, &badgeFontKey);
}
-(void)setBadgeFont:(UIFont *)badgeFont
{
    objc_setAssociatedObject(self, &badgeFontKey, badgeFont, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self refreshBadge];
    }
}

-(CGFloat) badgePadding {
    NSNumber *number = objc_getAssociatedObject(self, &badgePaddingKey);
    return number.floatValue;
}
-(void) setBadgePadding:(CGFloat)badgePadding
{
    NSNumber *number = [NSNumber numberWithDouble:badgePadding];
    objc_setAssociatedObject(self, &badgePaddingKey, number, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self updateBadgeFrame];
    }
}

-(CGFloat) badgeMinSize {
    NSNumber *number = objc_getAssociatedObject(self, &badgeMinSizeKey);
    return number.floatValue;
}
-(void) setBadgeMinSize:(CGFloat)badgeMinSize
{
    NSNumber *number = [NSNumber numberWithDouble:badgeMinSize];
    objc_setAssociatedObject(self, &badgeMinSizeKey, number, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self updateBadgeFrame];
    }
}

-(CGFloat) badgeOriginX {
    NSNumber *number = objc_getAssociatedObject(self, &badgeOriginXKey);
    return number.floatValue;
}
-(void) setBadgeOriginX:(CGFloat)badgeOriginX
{
    NSNumber *number = [NSNumber numberWithDouble:badgeOriginX];
    objc_setAssociatedObject(self, &badgeOriginXKey, number, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self updateBadgeFrame];
    }
}

-(CGFloat) badgeOriginY {
    NSNumber *number = objc_getAssociatedObject(self, &badgeOriginYKey);
    return number.floatValue;
}
-(void) setBadgeOriginY:(CGFloat)badgeOriginY
{
    NSNumber *number = [NSNumber numberWithDouble:badgeOriginY];
    objc_setAssociatedObject(self, &badgeOriginYKey, number, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    if (self.badge) {
        [self updateBadgeFrame];
    }
}

-(BOOL) shouldHideBadgeAtZero {
    NSNumber *number = objc_getAssociatedObject(self, &shouldHideBadgeAtZeroKey);
    return number.boolValue;
}
- (void)setShouldHideBadgeAtZero:(BOOL)shouldHideBadgeAtZero
{
    NSNumber *number = [NSNumber numberWithBool:shouldHideBadgeAtZero];
    objc_setAssociatedObject(self, &shouldHideBadgeAtZeroKey, number, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

-(BOOL) shouldAnimateBadge {
    NSNumber *number = objc_getAssociatedObject(self, &shouldAnimateBadgeKey);
    return number.boolValue;
}
- (void)setShouldAnimateBadge:(BOOL)shouldAnimateBadge
{
    NSNumber *number = [NSNumber numberWithBool:shouldAnimateBadge];
    objc_setAssociatedObject(self, &shouldAnimateBadgeKey, number, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

@end

之后调用就十分简单

//
//  ViewController.m
//  buttonBadge
//
//  Created by wuwj on 16/6/20.
//  Copyright © 2016年 wuwj. All rights reserved.
//

#import "ViewController.h"
#import "UIButton+Badge.h"
@interface ViewController (){
    UIButton *button;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIImage *image = [UIImage imageNamed:@"mail"];
    button = [UIButton buttonWithType:(UIButtonTypeCustom)];
    button.frame = CGRectMake(0, 0, 28, 18);
    [button setImage:image forState:(UIControlStateNormal)];
    button.badgeValue = @"一个信息";
    button.badgeBGColor = [UIColor cyanColor];
    button.badgeTextColor = [UIColor blackColor];
    [button addTarget:self action:@selector(change) forControlEvents:(UIControlEventTouchUpInside)];
    UIBarButtonItem *navButton = [[UIBarButtonItem alloc] initWithCustomView:button];
    self.navigationItem.leftBarButtonItem = navButton;
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)change{
    button.badgeValue = @"两个信息";
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

最后附上效果图片，哇咔咔，跑路。

badge.gif