Question

我正在尝试解析JSON文档并将其信息输入到UICollectionView中。我在处理UICollectionViewDelegate / Flowlayout / DataSource等之前测试了解析。它返回了正确的信息，但是现在我收到了这个错误。知道我在这里做错了吗？

class ViewModel {

let urlString = "https://s3.amazonaws.com/nxtapnxtap/clubsinfo.json"

var clubNames = [String]()
var smImg  = [UIImage]()
var lgImg = [String]()

func fetchItems(success: () -> ()) {
    let url = NSURL(string: urlString)
    let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
    let task = session.dataTaskWithURL(url!) { (data, response, error) in
        var jsonError: NSError?
    let json = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonError) as NSDictionary // Error here --> fatal error: unexpectedly found nil while unwrapping an Optional value

        if let unwrappedError = jsonError {
            println("jsonError: \(unwrappedError)")
        } else {
            self.clubNames = json.valueForKeyPath("entry.name.label") as [String]
            self.smImg = json.valueForKeyPath("entry.smimg.label") as [UIImage]
            self.lgImg = json.valueForKeyPath("entry.lgimg.label") as [String]
            success()
        }
    }
    task.resume()
}

Answer 1

从JSONObjectWithData返回的对象是nil。您正试图将其强制转换为NSDictionary。在对其进行操作之前，您需要检查它是否可以转换为NSDictionary：

func fetchItems(success: () -> ()) {
    let url = NSURL(string: urlString)
    let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
    let task = session.dataTaskWithURL(url!) { (data, response, error) in
        var jsonError: NSError?
        if let json = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonError) as? NSDictionary {
            self.clubNames = json.valueForKeyPath("entry.name.label") as [String]
            self.smImg = json.valueForKeyPath("entry.smimg.label") as [UIImage]
            self.lgImg = json.valueForKeyPath("entry.lgimg.label") as [String]
            success()
        } else if let unwrappedError = jsonError {
            println("jsonError: \(unwrappedError)")
        }
    }

    task.resume()
}

致命错误：在展开Optional值时意外发现nil

1 个答案: