Question

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        if collectionView == thisSeasonCollectionView {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as UICollectionViewCell

            let imageView = cell.viewWithTag(1) as! UIImageView

            let url = NSURL(string: URLArrayStringThisSeason[indexPath.row])

            let placeholderImage = UIImage(named: "Rectangle")!

            let filter = AspectScaledToFillSizeWithRoundedCornersFilter(
                size: imageView.frame.size,
                radius: 0
            )

            imageView.af_setImage(withURL: url as! URL, placeholderImage: placeholderImage, filter: filter, imageTransition: .crossDissolve(0.2)
            )
            cell.layer.cornerRadius = 3.0

            return cell
        }
        else if collectionView == whatsNewCollectionView {

            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as UICollectionViewCell

            let imageView = cell.viewWithTag(1) as! UIImageView

            let url = NSURL(string: URLArrayStringRecents[indexPath.row])

            let placeholderImage = UIImage(named: "Rectangle")!

            let filter = AspectScaledToFillSizeWithRoundedCornersFilter(
                size: imageView.frame.size,
                radius: 0
            )

            imageView.af_setImage(withURL: url as! URL, placeholderImage: placeholderImage, filter: filter, imageTransition: .crossDissolve(0.2)
            )

            cell.layer.cornerRadius = 3.0

            return cell
        }
    }

为什么这不起作用？我想尝试将3个集合视图从不同的tableView Cell链接到这个swift文件，但似乎只有两个。如果我因为某些原因将'else if'替换为'else'，代码工作正常。

修改：

如何编辑细胞计数的返回值：

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

        if collectionView == thisSeasonCollectionView {
            return URLArrayStringThisSeason.count
        }else if collectionView == whatsNewCollectionView {
            return URLArrayStringRecents.count
        }else if collectionView == labelCollectionView {
            return URLArrayStringLabel.count
        }

    }

Answer 1

将您的代码更改为以下内容：

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as UICollectionViewCell

    if collectionView == thisSeasonCollectionView {
        let imageView = cell.viewWithTag(1) as! UIImageView

        let url = NSURL(string: URLArrayStringThisSeason[indexPath.row])

        let placeholderImage = UIImage(named: "Rectangle")!

        let filter = AspectScaledToFillSizeWithRoundedCornersFilter(
            size: imageView.frame.size,
            radius: 0
        )

        imageView.af_setImage(withURL: url as! URL, placeholderImage: placeholderImage, filter: filter, imageTransition: .crossDissolve(0.2)
        )
        cell.layer.cornerRadius = 3.0
    }
    else if collectionView == whatsNewCollectionView {
        let imageView = cell.viewWithTag(1) as! UIImageView

        let url = NSURL(string: URLArrayStringRecents[indexPath.row])

        let placeholderImage = UIImage(named: "Rectangle")!

        let filter = AspectScaledToFillSizeWithRoundedCornersFilter(
            size: imageView.frame.size,
            radius: 0
        )

        imageView.af_setImage(withURL: url as! URL, placeholderImage: placeholderImage, filter: filter, imageTransition: .crossDissolve(0.2)
        )

        cell.layer.cornerRadius = 3.0
    }

    return cell
 }

在最后创建返回单元格，因为您只会点击一个语句，并且所有语句都需要返回一个单元格，因此不需要在三个不同的位置返回单元格，这足以将它放在最后。并且没有必要两次添加let cell = collectionView.dequeu...，一次就足够了。

Answer 2

并非上述代码中的所有控制路径都返回一个单元格。在'else if'body

之后添加另一个回报

Answer 3

您的代码归结为

function doSomething(a : Int) -> String {
    if a == 1 {
        return "something";
    } else if a == 2 {
        return "somethingElse";
    }
}

编译器会抱怨，因为如果a为3会发生什么？该方法不会返回任何内容。你可能知道a永远不会是3，但编译器不知道。

因此，要么将else if ...更改为简单的else，要使函数始终返回OR，或者在else if之后返回一些内容。

Answer 4

根据您在其他答案中发布的评论，您有三个（可能更多）集合视图，并希望拥有这样的代码结构：

array([[-3449.15531305,  4097.1707738 ,  1142.52971904,  1566.51333847],
       [ 4097.1707738 , -4863.70533241, -1356.66524959, -1860.15980716],
       [ 1142.52971904, -1356.66524959,  -378.32586814,  -518.71965102],
       [ 1566.51333847, -1860.15980716,  -518.71965102,  -711.21062988]])

您使用if collectionView == collectionView1 { // code that returns some cell } else if collectionView == collectionView2 { // code that returns some other cell } else if collectionView == collectionView3 { // code that returns yet another cell }而不是else if的原因是因为您希望稍后添加更多else。

然后我想，调用else if对你来说是最好的解决方案。

fatalError

这不仅会删除“没有所有代码路径返回值”错误，它还会提醒您是否忘记添加其他if！

此解决方案也可以应用于其他数据源方法！

Answer 5

谢谢大家，接下来我会尝试切换方法但是现在我找到了一个非常好的方法：

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        let cellCount = 0

        if collectionView == thisSeasonCollectionView {
            let cellCount = URLArrayStringThisSeason.count
            return cellCount
        }else if collectionView == whatsNewCollectionView {
            let cellCount = URLArrayStringRecents.count
            return cellCount
        }else if collectionView == labelCollectionView {
            let cellCount = URLArrayStringLabel.count
            return cellCount
        }
        return cellCount
    }

如何在任何viewController中添加三个或更多collectionViews

5 个答案: