[英]How to use computed property in a codable struct (swift)
我創建了一個“可編碼”結構來序列化數據集並將其編碼為Json。 除了計算屬性沒有顯示在json字符串中之外,一切都工作得很好。 如何在編碼階段包含計算屬性。
例如:
struct SolidObject:Codable{
var height:Double = 0
var width:Double = 0
var length:Double = 0
var volume:Double {
get{
return height * width * length
}
}
}
var solidObject = SolidObject()
solidObject.height = 10.2
solidObject.width = 7.3
solidObject.length = 5.0
let jsonEncoder = JSONEncoder()
do {
let jsonData = try jsonEncoder.encode(solidObject)
let jsonString = String(data: jsonData, encoding: .utf8)!
print(jsonString)
} catch {
print(error)
}
打印出“{”寬度“:7.2999999999999998,”長度“:5,”高度“:10.199999999999999}”
我也很好奇有7.29999 ..而不是7.3但我的主要問題是“我怎么能包括”音量“這個json字符串呢?”?
您需要手動編碼/解碼,而不是讓自動化的東西為您完成。 這在Swift游樂場中按預期工作。
struct SolidObject: Codable {
var height:Double = 0
var width:Double = 0
var length:Double = 0
var volume:Double {
get{
return height * width * length
}
}
enum CodingKeys: String, CodingKey {
case height
case width
case length
case volume
}
init() { }
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
height = try values.decode(Double.self, forKey: .height)
width = try values.decode(Double.self, forKey: .width)
length = try values.decode(Double.self, forKey: .length)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(height, forKey: .height)
try container.encode(width, forKey: .width)
try container.encode(length, forKey: .length)
try container.encode(volume, forKey: .volume)
}
}
var solidObject = SolidObject()
solidObject.height = 10.2
solidObject.width = 7.3
solidObject.length = 5.0
let jsonEncoder = JSONEncoder()
do {
let jsonData = try jsonEncoder.encode(solidObject)
let jsonString = String(data: jsonData, encoding: .utf8)!
print(jsonString)
} catch {
print(error)
}
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