改为使用sizeWithAttributes:，现在需要一个NSDictionary. 传入带有 key
的对UITextAttributeFont和你的字体对象，如下所示：

CGRect rawRect = {};
rawRect.size = [string sizeWithAttributes: @{
    NSFontAttributeName: [UIFont systemFontOfSize:17.0f],
}];

// Values are fractional -- you should take the ceil to get equivalent values
CGSize adjustedSize = CGRectIntegral(rawRect).size;