Question

我试图使用swift .prefix

将[String]数组限制为仅五个值

首先，我采用原始数组items并使用.prefix进行拼接

let testSlice = Array(items.prefix(5))
let newArray = Array(testSlice)

然后我验证了数组仅包含五个带有打印行的值。

print("DEV: newArray value: \(newArray)")

if newArray != [] {
    cell.profilePicture.playPortalProfilePic(forImageId: newArray[indexPath.item], { error in
        if let error = error {
            print("Error requesting profile pic: \(String(describing: error))")
        }
    })
} else {
    print("items array was empty, value: \(items)")
}

然后，将

newArray传递给我用来向profilePictures请求的SDK提供的方法。 newArray拥有这些值，因此[indexPath.item]在这里是合适的。当此功能正常运行时，它会根据数组中有多少个值在集合视图中创建单元格。

此行尝试运行Fatal error: Index out of range时，我目前看到cell.profilePicture.playPortalProfilePic(forImageId: newArray[indexPath.item]

编辑：注释请求的代码

 func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.items.count
    }

cell.profilePicture.playPortalProfilePic(forImageId: newArray[indexPath.item]行的完整方法

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

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! MyCollectionViewCell

        cell.profilePicture.layer.masksToBounds = true

        let testSlice = Array(items.prefix(5))
        let newArray = Array(testSlice)

        print("DEV: newArray value: \(newArray)")

        if newArray != [] {
            cell.profilePicture.playPortalProfilePic(forImageId: newArray[indexPath.item], { error in
                if let error = error {
                    print("Error requesting profile pic: \(String(describing: error))")
                }
            }
            )
        } else {
            print("items array was empty, value: \(items)")
        }


        cell.backgroundColor = UIColor.cyan
        cell.layer.borderColor = UIColor.black.cgColor
        cell.layer.borderWidth = 1
        cell.layer.cornerRadius = 8

        return cell
    }

Answer 1

您将items用作numberOfItemsInSection中的数据源，而在cellForItemAt内使用另一个newArray较小的prefix(5) 因此会导致崩溃，因此您应该在newArrray.count内返回numberOfItemsInSection的计数或单独使用testSlice

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