// 直接设置placeholder属性即可
    textView.placeholder = @"i love you";
    [self.view addSubview:textView];
    

/* 自动高度的方法，maxHeight：最大高度， textHeightDidChanged：高度改变的时候调用 */
- (void)autoHeightWithMaxHeight:(CGFloat)maxHeight textViewHeightDidChanged:(textViewHeightDidChangedBlock)textViewHeightDidChanged;

/* 添加一张图片 image:要添加的图片 */
- (void)addImage:(UIImage *)image;
/* 添加一张图片 image:要添加的图片 size:图片大小 */
- (void)addImage:(UIImage *)image size:(CGSize)size;
/* 插入一张图片 image:要添加的图片 size:图片大小 index:插入的位置 */
- (void)insertImage:(UIImage *)image size:(CGSize)size index:(NSInteger)index;

/* 添加一张图片 image:要添加的图片 multiple:放大／缩小的倍数 */
- (void)addImage:(UIImage *)image multiple:(CGFloat)multiple;
/* 插入一张图片 image:要添加的图片 multiple:放大／缩小的倍数 index:插入的位置 */
- (void)insertImage:(UIImage *)image multiple:(CGFloat)multiple index:(NSInteger)index;

// 占位文字
static const void *WZBPlaceholderViewKey = &WZBPlaceholderViewKey;
// 占位文字颜色
static const void *WZBPlaceholderColorKey = &WZBPlaceholderColorKey;
// 最大高度
static const void *WZBTextViewMaxHeightKey = &WZBTextViewMaxHeightKey;
// 高度变化的block
static const void *WZBTextViewHeightDidChangedBlockKey = &WZBTextViewHeightDidChangedBlockKey;
// 动态添加属性的本质是: 让对象的某个属性与值产生关联
objc_setAssociatedObject(self, WZBPlaceholderViewKey, placeholderView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
objc_setAssociatedObject(self, WZBTextViewMaxHeightKey, [NSString stringWithFormat:@"%lf", maxHeight], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, WZBTextViewHeightDidChangedBlockKey, textViewHeightDidChanged, OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, WZBPlaceholderColorKey, placeholderColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

    // 监听文字改变
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textViewTextChange) name:UITextViewTextDidChangeNotification object:self];
    // 这些属性改变时，都要作出一定的改变，尽管已经监听了TextDidChange的通知，也要监听text属性，因为通知监听不到setText：
    NSArray *propertys = @[@"frame", @"bounds", @"font", @"text", @"textAlignment", @"textContainerInset"];
    // 监听属性
    for (NSString *property in propertys) {
       [self addObserver:self forKeyPath:property options:NSKeyValueObservingOptionNew context:nil];
    }
    

- (void)textViewTextChange {
    self.placeholderView.hidden = (self.attributedText.length > 0 && self.attributedText);
    if (self.maxHeight >= self.bounds.size.height) {
        // 计算高度
        NSInteger currentHeight = ceil([self sizeThatFits:CGSizeMake(self.bounds.size.width, MAXFLOAT)].height);
        NSInteger lastheight = ceil(self.maxHeight + self.textContainerInset.top + self.textContainerInset.bottom);
        // 如果高度有变化，调用block
        if (currentHeight != lastheight) {
            
            self.scrollEnabled = currentHeight >= self.maxHeight;
            if (self.textViewHeightDidChanged) {
                self.textViewHeightDidChanged((currentHeight >= self.maxHeight ? self.maxHeight : currentHeight));
            }
        }
    }
}

- (void)addImage:(UIImage *)image size:(CGSize)size index:(NSInteger)index multiple:(CGFloat)multiple {
    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithAttributedString:self.attributedText];
    NSTextAttachment *textAttachment = [[NSTextAttachment alloc] init];
    textAttachment.image = image;
    CGRect bounds = textAttachment.bounds;
    if (!CGSizeEqualToSize(size, CGSizeZero)) {
        bounds.size = size;
        textAttachment.bounds = bounds;
    } else if (multiple > 0.0f) {
        textAttachment.image = [UIImage imageWithCGImage:textAttachment.image.CGImage scale:multiple orientation:UIImageOrientationUp];
    } else {
        CGFloat oldWidth = textAttachment.image.size.width;
        CGFloat scaleFactor = oldWidth / (self.frame.size.width - 10);
        textAttachment.image = [UIImage imageWithCGImage:textAttachment.image.CGImage scale:scaleFactor orientation:UIImageOrientationUp];
    }
    
    NSAttributedString *attrStringWithImage = [NSAttributedString attributedStringWithAttachment:textAttachment];
    [attributedString replaceCharactersInRange:NSMakeRange(index, 0) withAttributedString:attrStringWithImage];
    self.attributedText = attributedString;
    // 记得走下这两个方法
    [self textViewTextChange];
    [self refreshPlaceholderView];
}