新 Swift 更新后出现“下标使用不明确”错误

Question

My project was running fine before and still runs fine if using the simulator. But when I connect an iPhone and try and run the project I get this error: "Ambiguous use of subscript" when retrieving JSON info on this line:

 let channels = jsonResult["channels"]?[0] as? [String: AnyObject]

Any help to remedy this is appreciated!

Answer 1

The compiler seems to be more type restrictive.

The result type of jsonResult["channels"] is AnyObject you have to help the compiler by checking the value for being an array.

if let channels = jsonResult["channels"] as? [AnyObject], channel = channels[0] as? [String: AnyObject] {
  // do something with channel
}

Or still safer to check also whether the array is not empty

if let channels = jsonResult["channels"] as? [[String:AnyObject]] where !channels.isEmpty {
   let channel = channels[0] // now the compiler knows it's [String:AnyObject]
   // do something with channel
}