JSONDecorderは、プロパティdateDecodingStrategyをsetすると、dateのパース方法を色々カスタマイズできるみたい #CodePiece

CodePiece.swift

import Foundation

struct S1: Codable {
    let dateFromTimeInterval: Date
}

struct S2: Codable {
    let dateFromISO8601: Date
}

struct S3: Codable {
    let dateFromCustomFormat: Date
}

let data = """
{
    "dateFromTimeInterval": 540000000,
    "dateFromISO8601": "2017-01-01T12:34:56Z",
    "dateFromCustomFormat": "2034ねん03がつ04にち05じ06ふん07びょう",
}
""".data(using: .utf8)!

do {
    do {
        let decoder = JSONDecoder()
        let t = try decoder.decode(S1.self, from: data)
        print(t)
    }
    do {
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .iso8601
        let t = try decoder.decode(S2.self, from: data)
        print(t)
    }
    do {
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .formatted({
            let f = DateFormatter()
            f.calendar = Calendar(identifier: .gregorian)
            f.locale = .current
            f.dateFormat = "yyyyねんMMがつddにちHHじmmふんssびょう"
            return f
        }())

        let t = try decoder.decode(S3.self, from: data)
        print(t)
    }
    do {
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .custom {
            let container = try $0.singleValueContainer()
            let str = try container.decode(String.self)
            let f = DateFormatter()
            f.calendar = Calendar(identifier: .gregorian)
            f.locale = .current
            f.dateFormat = "yyyyねんMMがつddにちHHじmmふんssびょう"
            return f.date(from: str)!
        }
        let t = try decoder.decode(S3.self, from: data)
        print(t)
    }
} catch {
    print(error)
}

/* 結果
S1(dateFromTimeInterval: 2018-02-11 00:00:00 +0000)
S2(dateFromISO8601: 2017-01-01 12:34:56 +0000)
S3(dateFromCustomFormat: 2034-03-04 13:06:07 +0000)
S3(dateFromCustomFormat: 2034-03-04 13:06:07 +0000)
*/