一、Masonry实现自适应高度

/// 关键代码
CGFloat MIN_HEIGHT = 28.0f;
CGFloat MAX_HEIGHT = 60.0f;    

__block UIView *textContainerView = nil;   

[self.textView.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    if ([obj isKindOfClass:NSClassFromString(@"_UITextContainerView")]) {
            textContainerView = obj;
            *stop = YES;
        }
    }];

[self.textView mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.offset(TOP_HEIGHT+50);
    make.left.offset(50);
    make.right.offset(-50);
    make.height.mas_equalTo(textContainerView).priorityLow();
    make.height.mas_greaterThanOrEqualTo(MIN_HEIGHT);
    make.height.mas_lessThanOrEqualTo(MAX_HEIGHT);
}];

二、子类化实现自适应高度

/// 继承UITextView后重写下面方法
/// 关键代码
- (void)setContentSize:(CGSize)contentSize {
    [self invalidateIntrinsicContentSize];
    super.contentSize = contentSize;
}

- (CGSize)intrinsicContentSize {
    CGFloat MIN_HEIGHT = 28.0f;
    CGFloat MAX_HEIGHT = 60.0f;
    if (self.contentSize.height <= MIN_HEIGHT) {
        return CGSizeMake(self.contentSize.width, MIN_HEIGHT);
    }
    if (self.contentSize.height >= MAX_HEIGHT) {
        return CGSizeMake(self.contentSize.width, MAX_HEIGHT);
    }
    return self.contentSize;
}

/// 使用如下，设置相应约束即可
[self.view addSubview:self.textView];
[self.textView mas_makeConstraints:^(MASConstraintMaker *make) {
        make.top.offset(TOP_HEIGHT+50);
        make.left.offset(50);
        make.right.offset(-50);
    }];