在可编码类中声明空字典

Question

我想这样发送空字典

“visitor_attrs”: {
}

我尝试在一个类中实现空字典。在解码器中，我收到了一些警告，因为没有“解码”候选者会产生预期的上下文结果类型“字典” 。我该怎么办？

var data: String
var event: String
var visitorAttrs: Dictionary<String, Any>

init(data: String, event: String) {
    self.data = data
    self.event = event
    self.visitorAttrs = [:]
}

private enum CodingKeys: String, CodingKey {
    case data
    case event
    case visitorAttrs = "visitor_attrs"
}

required public init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    self.data = try container.decode(String.self, forKey: .data)
    self.event = try container.decode(String.self, forKey: .event)
    self.visitorAttrs = try container.decode(Dictionary<String:Any>.self, forKey: .visitorAttrs)
}

public func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(self.data, forKey: .data)
    try container.encode(self.event, forKey: .event)
    try container.encode(self.visitorAttrs, forKey: .visitorAttrs)
}