作者:靠谱同学轻松1988 | 来源:互联网 | 2023-02-01 07:57
我如何使用Codable
解码JSON并在创建对象(而不是结构)时交叉引用它们?在这个例子中,我希望Painting
该类具有Color
在JSON中定义的对象数组.(我也希望能够将它们编码回JSON.)
额外奖励:在这种情况下,我宁愿选择Painting.colors
非可选let
属性而不是 var
.我不希望它在创作后改变,我不希望它永远是零.(我宁愿使用空数组的默认值而不是nil.)
class Art: Codable {
var colors: [Color]?
var Paintings: [Painting]?
}
class Color: Codable {
var id: String?
var hex: String?
}
class Painting: Codable {
var name: String?
var colors: [Color]?
}
let json = """
{
"colors": [
{"id": "black","hex": "000000"
},
{"id": "red", "hex": "FF0000"},
{"id": "blue", "hex": "0000FF"},
{"id": "green", "hex": "00FF00"},
{"id": "yellow", "hex": "FFFB00"},
{"id": "orange", "hex": "FF9300"},
{"id": "purple", "hex": "FF00FF"}
],
"paintings": [
{
"name": "Starry Night",
"colorIds": ["blue", "black", "purple", "yellow"]
},
{
"name": "The Scream",
"colorIds": ["orange", "black", "blue"]
},
{
"name": "Nighthawks",
"colorIds": ["green", "orange", "blue", "yellow"]
}
]
}
"""
let data = json.data(using: .utf8)
let art = try JSONDecoder().decode(Art.self, from: data!)
我考虑过的一些方法:
手动编码/解码 json.看起来像很多额外的工作但也许它给了我需要的控制权?
将JSON解码分解为多个步骤.将JSON反序列化为字典,首先拉出并解码颜色,然后绘制(可以访问上下文中的颜色).这感觉就像打架Codable
,希望你一次解码所有Data
,而不是Dictionary
.
有Painting
动态发现Color
通过动态属性在运行时秒.但在开始真正的工作之前,我宁愿让所有的对象关系建立和验证,然后永远不会改变.但也许这会是最简单的?
不使用Codable
其他一些不好的想法
Code Differe..
7
我投票重新打开你的问题,因为虽然JSON不方便Codable
,但它可以完成.您将不得不手动解码JSON,以便问题变成:最难以实现的方法是什么?
我的经验法则是:不要与JSON作斗争.将其原样导入Swift值,然后您可以对其进行各种操作.为此,让我们定义一个RawArt
紧跟JSON 的结构:
fileprivate struct RawArt: Decodable {
struct RawPainting: Codable {
var name: String
var colorIds: [String]
}
var colors: [Color] // the Color class matches the JSON so no need to define a new struct
var paintings: [RawPainting] // the Painting class does not so we need a substitute struct
}
现在将原始JSON对象转换为您的类:
class Art: Codable {
var colors: [Color]
var paintings: [Painting]
required init(from decoder: Decoder) throws {
let rawArt = try RawArt(from: decoder)
self.colors = rawArt.colors
self.paintings = rawArt.paintings.map { rawPainting in
let name = rawPainting.name
let colors = rawPainting.colorIds.flatMap { colorId in
rawArt.colors.first(where: { $0.id == colorId })
}
return Painting(name: name, colors: colors)
}
}
}
class Color: Codable {
var id: String
var hex: String
init(id: String, hex: String) {
self.id = id
self.hex = hex
}
}
// It does not transform into the JSON you want so you may as well remove Codable conformance
class Painting: Codable {
var name: String
var colors: [Color]
init(name: String, colors: [Color]) {
self.name = name
self.colors = colors
}
}
要测试它实际引用一个Color
对象:
let data = json.data(using: .utf8)
let art = try JSONDecoder().decode(Art.self, from: data!)
art.colors[0].id = "new_black"
print(art.paintings[0].colors[1].id) // the second color in Starry Night: new_black
一切都是非可选的,从JSON中取消归档对象只需不到20行代码.
1> Code Differe..:
我投票重新打开你的问题,因为虽然JSON不方便Codable
,但它可以完成.您将不得不手动解码JSON,以便问题变成:最难以实现的方法是什么?
我的经验法则是:不要与JSON作斗争.将其原样导入Swift值,然后您可以对其进行各种操作.为此,让我们定义一个RawArt
紧跟JSON 的结构:
fileprivate struct RawArt: Decodable {
struct RawPainting: Codable {
var name: String
var colorIds: [String]
}
var colors: [Color] // the Color class matches the JSON so no need to define a new struct
var paintings: [RawPainting] // the Painting class does not so we need a substitute struct
}
现在将原始JSON对象转换为您的类:
class Art: Codable {
var colors: [Color]
var paintings: [Painting]
required init(from decoder: Decoder) throws {
let rawArt = try RawArt(from: decoder)
self.colors = rawArt.colors
self.paintings = rawArt.paintings.map { rawPainting in
let name = rawPainting.name
let colors = rawPainting.colorIds.flatMap { colorId in
rawArt.colors.first(where: { $0.id == colorId })
}
return Painting(name: name, colors: colors)
}
}
}
class Color: Codable {
var id: String
var hex: String
init(id: String, hex: String) {
self.id = id
self.hex = hex
}
}
// It does not transform into the JSON you want so you may as well remove Codable conformance
class Painting: Codable {
var name: String
var colors: [Color]
init(name: String, colors: [Color]) {
self.name = name
self.colors = colors
}
}
要测试它实际引用一个Color
对象:
let data = json.data(using: .utf8)
let art = try JSONDecoder().decode(Art.self, from: data!)
art.colors[0].id = "new_black"
print(art.paintings[0].colors[1].id) // the second color in Starry Night: new_black
一切都是非可选的,从JSON中取消归档对象只需不到20行代码.