Question

我得到以下代码，我从我的sql表中选择一个随机值，但我想阻止它选择重复。

private var cachedDecorationView = [UICollectionViewLayoutAttributes]()
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        //Tip: layoutAtributes with the same indexPath may can not be allowed for reusing
        guard let atributes = super.layoutAttributesForElements(in: rect) else {
            return nil
        }
        var mutatingAtributes = atributes

        //find max Y position of the cells
        var position = CGRect.zero
        position.size.width = rect.size.width
        position.size.height = shelfSize

        for atribute in mutatingAtributes {
            atribute.zIndex = 1
            if atribute.frame.maxY > position.origin.y {
                position.origin.y = atribute.frame.maxY
                if rect.intersects(position) {
                    let shelf = prerareShelves(for: position)
                    mutatingAtributes.append(shelf)
                }

            }
        }

        return mutatingAtributes
    }

    func prerareShelves(for rect: CGRect) -> UICollectionViewLayoutAttributes {
        for cache in cachedDecorationView {
            if cache.frame == rect {
                return cache
            }
        }
        let indexForNewDecoration = Int(rect.origin.y/itemSize.height + shelfSize)
        let decoratorView = layoutAttributesForDecorationView(ofKind: DecorationViewKind.shelfView.rawValue, at: IndexPath(item: indexForNewDecoration, section: 0))!
        decoratorView.frame = rect
        cachedDecorationView.append(decoratorView)
        return decoratorView
    }
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return collectionView?.bounds.size != newBounds.size
    }

    override func invalidateLayout() {
        super.invalidateLayout()
        //delete all cached decoration views before new layout process
        cachedDecorationView.removeAll()
    }

在这种情况下，目标就像是火种。你得到一张随机图片（在一个随机的人身上）并投票，但那时已经投票的图片不应该从我的表中重新选择。我的目标是将所选值与用户表中的值进行比较，其中每个id都标记为已经由他投票。有没有人知道如何实现这样的目标？

最诚挚的问候！

Answer 1

您需要为用户perviews创建一个表，该表存储之前为此用户检索的数字

用户表

+------+--------+--------+
|USERID|USERDATA|USERDATA|
+------+--------+--------+
|1     |  XXXX  |  XXXX  |
+------+--------+--------+
|2     |  AAAA  |  AAAA  |
+------+--------+--------+
|3     |  ZZZZ  |  ZZZZ  |
+------+--------+--------+

用户视图表

+------+---------+
|USERID|pictureID|
+------+---------+
|1     |     1   |
+------+---------+
|1     |     2   |
+------+---------+
|2     |     3   |
+------+---------+
|3     |     3   |
+------+---------+
|3     |     2   |
+------+---------+

图片表

+----------+----+
|PICTUIREID|DATA|
+----------+----+
|1         |WWWW| 
+----------+----+
|2         |EEEE|  
+----------+----+
|3         |RRRR|  
+----------+----+

然后你的查询将是

SELECT p.pictureID FROM Userviews uv
join picture p on p.PICTUIREID = uv.PICTUIREID 
where uv.USERID <> (userID )
 ORDER BY RAND() LIMIT 1"

如何将mysql数据库中的选定值与另一个表中的现有值进行比较？

1 个答案: