iOS开发中经常需要在富文本（NSAttributedString）中添加图片（NSTextAttachment）。那么如何添加图片呢？代码如下
UIFont *font = [UIFont systemFontOfSize:12];
NSDictionary<NSAttributedStringKey,id> *attributes = @{
NSFontAttributeName: font,
};
//生成富文本
NSMutableAttributedString *attributedText = [[NSMutableAttributedString alloc] initWithString:@"我忘记了" attributes:attributes];
//添加图片
[attributedText appendAttributedString:({
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
UIImage *image = [UIImage imageNamed:@"icon"];
attachment.image = image;
attachment.bounds = CGRectMake(0, 0, image.size.width, image.size.height);
[NSAttributedString attributedStringWithAttachment:attachment];
})];
代码写好了，编译运行，看看效果:
运行效果1
这肯定不是设计师需要的效果，如何让文字和图片在竖直方向上居中对齐呢？其实很简单，修改
attachment.bounds.origin.y即可：
UIFont *font = [UIFont systemFontOfSize:12];
NSDictionary<NSAttributedStringKey,id> *attributes = @{
NSFontAttributeName: font,
};
//生成富文本
NSMutableAttributedString *attributedText = [[NSMutableAttributedString alloc] initWithString:@"我忘记了" attributes:attributes];
//添加图片
[attributedText appendAttributedString:({
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
UIImage *image = [UIImage imageNamed:@"icon"];
attachment.image = image;
attachment.bounds = CGRectMake(0, -4.5, image.size.width, image.size.height);
[NSAttributedString attributedStringWithAttachment:attachment];
})];
设置好attachment.bounds.origin.y了，再重新编译运行看看效果：
运行效果2
效果不错，达到了设计师需要的效果。那么问题来了，为何要设置
attachment.bounds.origin.y = -4.5呢？我试了十遍试出来的
每次新添加或者切换字体都试上十遍，肯定不是我们想要的，那有没有更好的方式呢？答案肯定是有的，设置
attachment.bounds.origin.y = round(font.capHeight - image.size.height)/2.0即可：
UIFont *font = [UIFont systemFontOfSize:12];
NSDictionary<NSAttributedStringKey,id> *attributes = @{
NSFontAttributeName: font,
};
//生成富文本
NSMutableAttributedString *attributedText = [[NSMutableAttributedString alloc] initWithString:@"我忘记了" attributes:attributes];
//添加图片
[attributedText appendAttributedString:({
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
UIImage *image = [UIImage imageNamed:@"icon"];
attachment.image = image;
attachment.bounds = CGRectMake(0, round(font.capHeight - image.size.height)/2.0, image.size.width, image.size.height);
[NSAttributedString attributedStringWithAttachment:attachment];
})];
再次编译运行得到我们想要的效果：
最终效果
参考：https://stackoverflow.com/questions/26105803/center-nstextattachment-image-next-to-single-line-uilabel
关于bound的设置可参考：https://www.jianshu.com/p/964313cfbdaa
