Swift 映射数组意外参数类型

Question

我有以下带有地图的代码，为什么 log 也是一个数组而不只是一个 CKRecord 对象？

sharedDatabase.perform(query, inZoneWith: nil) { (records, error) in
  if let error = error {
    reject("there is error", "no logs", error)
  }else{
    NSLog("found results")
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
    let resultLogs = records.map { log in
      // Log is also an array: [CKRecorder] so I'll get error:
      // Value of type '[CKRecord]' has no member 'object'
      return [
        "log": log.object(forKey: "log") ?? "N/A" as __CKRecordObjCValue,
        "createdAt": formatter.string(from: log.creationDate ?? Date.init())
      ]
    }
    resolve(resultLogs)
  }

Answer 1

Because the map function also exists on Optional。请注意 records 后缺少 ?。您可能想先将它解包在 guard 中，或者添加 ? 以在整个表达式上使用可选链接。

Answer 2

当您使用 return 一个可选值和一个可选错误的完成处理程序时，您应该始终可选地绑定该值，同时检查错误是否为 nil。这将解决您尝试调用 Optional 的 map 而不是 Array.

的问题。

sharedDatabase.perform(query, inZoneWith: nil) { (records, error) in
    guard let records = records, error == nil else {
        return reject("there is error", "no logs", error!)
    }
    NSLog("found results")
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
    let resultLogs = records.map { log in
      return [
        "log": log.object(forKey: "log") ?? "N/A" as __CKRecordObjCValue,
        "createdAt": formatter.string(from: log.creationDate ?? Date())
      ]
    }
    resolve(resultLogs)
}

Swift 映射数组意外参数类型

Swift map array unexpected argument type

arrays

swift

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