var cellHeights: [CGFloat] = [CGFloat]()
if let height = self.cellHeights[index] as? CGFloat {
self.cellHeights[index] = cell.frame.size.height
} else {
self.cellHeights.append(cell.frame.size.height)
}
我需要检查指定索引处的元素是否存在。然而,上述代码不起作用,我得到了构建错误:
我也尝试过:从CGFloat到CGFloat的条件下转换总是成功
if let height = self.cellHeights[index] {}
但是这也失败了:
Bound value in a conditional binding must be of Optional type
有什么想法是错的吗?