如果没有更多的上下文，表达的类型是不明确的

Question

class func unarchiveFromFile(file : NSString) -> SKNode? {

    let path = NSBundle.mainBundle().pathForResource(file as String, ofType: "sks")

    var sceneData = NSData.dataWithContentsOfFile(path, options: .DataReadingMappedIfSafe!, error: nil)
    var archiver = NSKeyedUnarchiver(forReadingWithData: sceneData)

    archiver.setClass(self.classForKeyedUnarchiver(), forClassName: "SKScene")
    let scene = archiver.decodeObjectForKey(NSKeyedArchiveRootObjectKey) as GameScene
    archiver.finishDecoding()
    return scene

所以我在var sceneData = NSData上得到一个错误：表达的类型含糊不清，有更多的上下文。我非常困难

Answer 1

pathForResource会返回一个可选项 dataWithContentsOfFile期望非可选。

展开可选

let path = NSBundle.mainBundle().pathForResource(file as String, ofType: "sks")!

或执行可选绑定

if let path = NSBundle.mainBundle().pathForResource(file as String, ofType: "sks") {
 // path is safe
}

实际上dataWithContentsOfFile的正确语法是

let sceneData = NSData(contentsOfFile:path, options: .DataReadingMappedIfSafe, error: nil)

并且.DataReadingMappedIfSafe永远不需要打开。

编辑：

完整代码：

class func unarchiveFromFile(file : NSString) -> SKNode? {

    if let path = NSBundle.mainBundle().pathForResource(file as String, ofType: "sks") {
        // path is safe
        let sceneData = NSData(contentsOfFile:path, options: .DataReadingMappedIfSafe, error: nil)
        var archiver = NSKeyedUnarchiver(forReadingWithData: sceneData)

        archiver.setClass(self.classForKeyedUnarchiver(), forClassName: "SKScene")
        let scene = archiver.decodeObjectForKey(NSKeyedArchiveRootObjectKey) as GameScene
        archiver.finishDecoding()
        return scene
    }
    return nil
}