xcode - Swift 错误解析 Facebook Graph API 对象 : EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP)

Question

我在尝试获取 Facebook 群组信息时遇到错误，我不知道如何修复。

当我尝试访问群组提要的单个项目时，我将提要从 AnyObject 转换为 FBGraphObject，这就是错误发生的地方。

错误显示为“Thread 1 : EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP, subcode=0x0)”

我尝试进行 nil 检查，并检查对象的类型以防止错误，但并没有解决问题。

任何建议可能是什么问题？

func fetchFacebookGroup() {
    FBRequestConnection.startWithGraphPath("/\(groupId)/?fields=feed", completionHandler: {(connection: FBRequestConnection!, result: AnyObject!, error: NSError!) -> Void in
        if result? {
            NSLog("error = \(error)")

            var jsonFeeds = result as FBGraphObject
            self.feeds = self.buildFeeds((jsonFeeds["feed"] as FBGraphObject)["data"] as NSMutableArray)
            self.tableView.reloadData()
        }
        } as FBRequestHandler)

}

func buildFeeds(data: NSMutableArray) -> Array<GroupFeed> {
    var result : Array<GroupFeed> = []
    for rawFeed : AnyObject in data {
        if rawFeed is FBGraphObject { // This is where error pops up.
            if let jsonFeed = rawFeed as? FBGraphObject {
                var feed = GroupFeed(id: jsonFeed["id"] as String, name: (jsonFeed["from"] as FBGraphObject)["name"] as String, message: jsonFeed["message"] as String, updatedTime: jsonFeed["updated_time"] as String)
                result.append(feed)
            }
        }
    }

    return result
}

Answer 1

我在解析 API 调用返回的 FBGraphObject 时更加小心，从而解决了这个问题。事实证明，我错误地假设此 API 返回的所有群组订阅源都包含“消息”作为键。

因此我的代码的固定版本工作如下:

TableViewController.swift

func fetchFacebookGroup() {
    FBRequestConnection.startWithGraphPath("\(groupId)/?fields=feed.limit=(1)", completionHandler: {(connection: FBRequestConnection!, result: AnyObject!, error: NSError!) -> Void in
        if result? {
            NSLog("error = \(error)")

            var jsonFeeds = result as FBGraphObject
            self.feeds = self.buildFeeds((jsonFeeds["feed"] as FBGraphObject)["data"] as NSMutableArray)
            self.tableView.reloadData()
        }
        } as FBRequestHandler)

}

func buildFeeds(data: NSMutableArray) -> Array<GroupFeed> {
    var result : Array<GroupFeed> = []
    for rawFeed : AnyObject in data {
        if rawFeed is FBGraphObject {
            if let jsonFeed = rawFeed as? FBGraphObject {
                var feed = GroupFeed(jsonFeed: jsonFeed)
                result += feed
            }
        }
    }
    return result
}

GroupFeed.swift

class GroupFeed: NSObject {
    var id : String!
    var name : String!
    var message : String?
    var updatedTime : String!

    init(jsonFeed: FBGraphObject) {
        self.id = jsonFeed["id"] as String
        self.name = (jsonFeed["from"] as FBGraphObject)["name"] as String
        if let message = jsonFeed.objectForKey("message") as? String {
            self.message = message
        }
        self.updatedTime = jsonFeed["updated_time"] as String
    }
}

所以我在这里的教训是，我不应该过分依赖 XCode 调试器的能力来查明错误的确切来源。

我不知道这是因为 XCode6 仍处于测试阶段，还是它就是这样，但是在测试版 IDE 上使用一种全新的语言时，应该注意不要盲目信任该工具.