在swift中过滤API中的空值

Question

我试图在swift(UIKit)中以json格式从api中过滤出空值和null值。完整的数据返回如下所示，但有时characteristic键中可能包含空值或空值。总是有相同数量的键

//Cat
{
"breedname": "Persian",
"picture": "https://catimage.random.png",
"characteristic1": "Shy",
"characteristic2": "Hungry all the time"
"characteristic3": "Likes apples"
"characteristic4": "Grey color"
"characteristic5": "likes chin scratches"
}
{
"breedname": "Bengal",
"picture": "https://catimage.random.png",
"characteristic1": "Active",
"characteristic2": "Adventurous"
"characteristic3": ""
"characteristic4": ""
"characteristic5": ""
}
{
"breedname": "ragdoll",
"picture": "https://catimage.random.png",
"characteristic1": "Fiestey",
"characteristic2": "sharp claws"
"characteristic3": null
"characteristic4": null
"characteristic5": null
}

为了在UI中显示之前过滤空值和空值，我有一个像下面这样的可解码类和一个带有decodeifPresent方法的自定义初始化类，它将空值更改为nil。然而，对于空值，我只是创建了一个将空字符串值转换为nil的方法。我不确定是否有更好的方法来处理空和null数据并过滤掉它们?我在UI中引用了所有可解码的键，所以我不能简单地删除键本身。

struct Cat: Decodable {

let breedName: String
let picture: String
let characteristic1 : String?
let characteristic2 : String?
let characteristic3 : String?
let characteristic4 : String?
let characteristic5 : String?
enum CodingKeys: String, CodingKey {
case breedName
case picture
case characteristic1
case characteristic2
case characteristic3
case characteristic4
case characteristic5
}
func checkEmpty(s: String?) -> String? {
if s == "" {
return nil
}
return s
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.breedName= try container.decode(String.self, forKey: .breedName)
self.picture = try container.decode(String.self, forKey: .picture)
self.characteristic1 = try container.decodeIfPresent(String.self, forKey: .characteristic1)
self.characteristic2 = try container.decodeIfPresent(String.self, forKey: .characteristic2)
self.characteristic3 = try container.decodeIfPresent(String.self, forKey: .characteristic3)
self.characteristic4 = try container.decodeIfPresent(String.self, forKey: .characteristic4)
self.characteristic5 = try container.decodeIfPresent(String.self, forKey: .characteristic5)
self.characteristic1 = checkEmpty(s: self.characteristic1)
self.characteristic2 = checkEmpty(s: self.characteristic2)
self.characteristic3 = checkEmpty(s: self.characteristic3)
self.characteristic4 = checkEmpty(s: self.characteristic4)
self.characteristic5 = checkEmpty(s: self.characteristic5)

Answer 1

一个解决方案是检查在String

扩展中定义的函数是否为空

extension String {
func emptyAsNil() -> String? {
self.isEmpty ? nil : self
}
}

那么你可以在init

中一步完成所有操作

self.characteristic1 = try container.decodeIfPresent(String.self, forKey: .characteristic1)?.emptyAsNil()

但也许更好的解决方案是将所有这些属性收集到一个集合中，如数组或字典。这里我选择了一个数组

struct Cat: Decodable {
let breedName: String
let picture: String
var characteristics: [String]
}

然后在init中我们只向数组

中添加非空值

if let value = try container.decodeIfPresent(String.self, forKey: .characteristic1), !value.isEmpty {
characteristics.append(value)
}

或者另一种方法是遍历键

let keys: [CodingKeys] = [.characteristic1,
.characteristic2,
.characteristic3,
.characteristic4,
.characteristic5]
for key in keys {
if let value = try container.decodeIfPresent(String.self, forKey: key), !value.isEmpty {
characteristics.append(value)
}
}