因为添加空白占位符，导致高度计算不对，尤其是在10个汉字的时候

[Coder-Miao]

不知道基于什么考虑，添加了这些代码
unichar spacingChar = 0xFFFC;
NSString *spacingCharString = [NSString stringWithCharacters:&spacingChar length:1];
//空白占位符
NSAttributedString *placeholderStr = [[NSAttributedString alloc]initWithString:spacingCharString];
[str appendAttributedString:placeholderStr];