设置button 文字居左，图片居右

//设置图片居右
-(void)setImageToRight
{
    NSDictionary *attribute = @{NSFontAttributeName:btn.titleLabel.font};
    //获取文本的宽度
    CGFloat btnWidth = [btn.titleLabel.text boundingRectWithSize:CGSizeMake(0, 24)
                                                         options:\
                        NSStringDrawingTruncatesLastVisibleLine |
                        NSStringDrawingUsesLineFragmentOrigin |
                        NSStringDrawingUsesFontLeading
                                                      attributes:attribute
                                                         context:nil].size.width;
    
    
    //通过调节文本和图片的内边距到达目的
    btn.imageEdgeInsets = UIEdgeInsetsMake(0, btnWidth, 0, -btnWidth);
    [btn setTitleEdgeInsets:UIEdgeInsetsMake(0, -btn.imageView.image.size.width, 0, btn.imageView.image.size.width)];
}