IOS Auto Layout 二 -UIStackView

#pragma mark - 减少点击
-(void)btnReduceClick{
    [UIView animateWithDuration:0.5f
                          delay:0.0f
         usingSpringWithDamping:0.7f
          initialSpringVelocity:5.0f
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^{
                            NSArray *subviewArrays = self.stackStars.arrangedSubviews;
                            if(subviewArrays.count != 0){
                                UIView* view = self.stackStars.arrangedSubviews.lastObject;
                                [self.stackStars removeArrangedSubview:view];
                                [view removeFromSuperview];
                            }
                     } completion:^(BOOL finished) {
                         
                     }];
}

#pragma mark - 增加点击
-(void)btnAddClick{
    [UIView animateWithDuration:0.5f
                          delay:0.0f
         usingSpringWithDamping:0.7f
          initialSpringVelocity:5.0f
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^{
                            UIImageView *imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"icon_star"]];
                            imageView.contentMode = UIViewContentModeCenter;
                            [self.stackStars addArrangedSubview:imageView];
                     } completion:^(BOOL finished) {
                         
                     }];
}

参考文献：
iOS9之UIStackView体验,无需任何约束，这才是真正的自动布局，快到不能呼吸
 An Introduction to Stack Views in iOS 9 and Xcode 7
iOS 9: UIStackView入门