我需要解析其中一个字段值是数组的JSON:
"list" :
[
{
"value" : 1
}
]
或一个空字符串,以防没有数据:
"list" : ""
不好,但是我不能更改格式。
我正在考虑将我的手动解析(这很容易)转换为
JSONDecoder
和Codable
struct
。我该如何处理这种令人讨厌的不一致?
最佳答案
您需要尝试以一种方式对其进行解码,如果失败,则以另一种方式进行解码。这意味着您不能使用编译器生成的解码支持。你必须手工做。如果要进行全面的错误检查,请执行以下操作:
import Foundation
struct ListItem: Decodable {
var value: Int
}
struct MyResponse: Decodable {
var list: [ListItem] = []
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
do {
list = try container.decode([ListItem].self, forKey: .list)
} catch {
switch error {
// In Swift 4, the expected type is [Any].self, but I think it will be [ListItem].self in a newer Swift with conditional conformance support.
case DecodingError.typeMismatch(let expectedType, _) where expectedType == [Any].self || expectedType == [ListItem].self:
let dummyString = try container.decode(String.self, forKey: .list)
if dummyString != "" {
throw DecodingError.dataCorruptedError(forKey: .list, in: container, debugDescription: "Expected empty string but got \"\(dummyString)\"")
}
list = []
default: throw error
}
}
}
enum CodingKeys: String, CodingKey {
case list
}
}
如果您不希望进行错误检查,则可以将
init(from:)
缩短为: init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
list = (try? container.decode([ListItem].self, forKey: .list)) ?? []
}
测试1:
let jsonString1 = """
{
"list" : [ { "value" : 1 } ]
}
"""
print(try! JSONDecoder().decode(MyResponse.self, from: jsonString1.data(using: .utf8)!))
输出1:
MyResponse(list: [__lldb_expr_82.ListItem(value: 1)])
测试2:
let jsonString2 = """
{
"list" : ""
}
"""
print(try! JSONDecoder().decode(MyResponse.self, from: jsonString2.data(using: .utf8)!))
输出2:
MyResponse(list: [])