Swift 2.0：没有更多上下文，表达式类型不明确？

Question

以下用于 Swift 1.2：

var recordSettings = [
    AVFormatIDKey: kAudioFormatMPEG4AAC,
    AVEncoderAudioQualityKey : AVAudioQuality.Max.rawValue,
    AVEncoderBitRateKey : 320000,
    AVNumberOfChannelsKey: 2,
    AVSampleRateKey : 44100.0]

现在，它给出错误：

"Type expression is ambiguous without more context".

Answer 1

你可以给编译器更多的信息：

let recordSettings : [String : Any] =
[
    AVFormatIDKey: kAudioFormatMPEG4AAC,
    AVEncoderAudioQualityKey : AVAudioQuality.Max.rawValue,
    AVEncoderBitRateKey : 320000,
    AVNumberOfChannelsKey: 2,
    AVSampleRateKey : 44100.0
]

Answer 2

遵守recordSettings参数要求的[String : AnyObject]格式；除了@Unheilig 的回答之外，您还需要将 ints 和 floats 转换为 NSNumber:

let recordSettings : [String : AnyObject] =
[
    AVFormatIDKey: NSNumber(unsignedInt: kAudioFormatMPEG4AAC),
    AVEncoderAudioQualityKey : AVAudioQuality.Max.rawValue as NSNumber,
    AVEncoderBitRateKey : 320000 as NSNumber,
    AVNumberOfChannelsKey: 2 as NSNumber,
    AVSampleRateKey : 44100.0 as NSNumber
]

Answer 3

我还收到此错误消息，试图用 nil 初始化可选数组：

var eggs : [Egg] = Array<Egg>(count: 10, repeatedValue: nil)

Expression Type 'Array<Egg>' is ambiguous without more context.

将 [Egg] 更改为 [Egg?] 修复了错误。