Swift 使用JSONDecoder 将data转为model

如下 json 数据

{
    "movie_detail":
        {
            "movie_thumbnail_image":"https://bkimg.cdn.bcebos.com/pic/aa18972bd40735fae6cd4657120318b30f2443a7a299?x-bce-process=image/resize,m_lfit,w_440,limit_1/format,f_auto",
            "title":"长津湖",
            "synopsis":"《长津湖》是由陈凯歌、徐克、林超贤联合执导，吴京、易烊千玺领衔主演，段奕宏、欧豪特别出演，朱亚文、李晨、胡军、韩东君等主演的抗美援朝电影 ，该片于2021年9月30日在中国大陆上映。该片以抗美援朝战争第二次战役中的长津湖战役为背景，讲述了一段波澜壮阔的历史，在极寒严酷环境下，中国人民志愿军东线作战部队凭着钢铁意志和英勇无畏的战斗精神，扭转战场态势，为长津湖战役胜利作出重要贡献的故事。",
            "theater":["A影院","B影院","C影院"],
            "comments":
                [
                    {"user_name":"user001","rating":"5","comment":"评论1！"},
                    {"user_name":"user002","rating":"5","comment":"评论2！"},
                    {"user_name":"user003","rating":"4","comment":"评论3！"}
                ]
        }
}

可以将此 json 数据分为三个模型 MovieDetailDic，MovieDetail，Comment

首先建立一个 struct 类型的 model -> MovieDetailDic 遵循 Decodable 协议，通过 CodingKey 将模型变量和 json 的 key 对应

struct MovieDetailDic: Decodable {
    private enum CodingKeys: String, CodingKey {
        case movieDetail = "movie_detail"
    }
    
    let movieDetail: MovieDetail?
    
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        movieDetail = try values.decodeIfPresent(MovieDetail.self, forKey: .movieDetail)
    }
}

将 json 数据 “movie_detail” 对应的 value 建立为 MovieDetail 模型。 变量要和 json 的 key 相对应， 变量名可以自定义， 但是要在 CodingKeys 中将变量名和 key 关联起来， 如【case movieThumbnailImage = "movie_thumbnail_image"】， 如果变量名 和 key 相同，可不做处理。

struct MovieDetail: Decodable {
    private enum CodingKeys: String, CodingKey {
        case movieThumbnailImage = "movie_thumbnail_image"
        case title
        case synopsis
        case theater
        case comments
    }
    
    let movieThumbnailImage: String?
    let title: String?
    let synopsis: String?
    let theater: [String]?
    let comments: [Comment]?

    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        title = try values.decodeIfPresent(String.self, forKey: .title)
        movieThumbnailImage = try values.decodeIfPresent(String.self, forKey: .movieThumbnailImage)
        synopsis = try values.decodeIfPresent(String.self, forKey: .synopsis)
        theater = try values.decodeIfPresent([String].self, forKey: .theater)
        comments = try values.decodeIfPresent([Comment].self, forKey: .comments)
    }
}

建立 comment 模型

struct Comment: Decodable {
    private enum CodingKeys: String, CodingKey {
        case userName = "user_name"
        case rating
        case comment
    }
    
    let userName: String?
    let rating: String?
    let comment: String?
    
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        userName = try values.decodeIfPresent(String.self, forKey: .userName)
        rating = try values.decodeIfPresent(String.self, forKey: .rating)
        comment = try values.decodeIfPresent(String.self, forKey: .comment)
    }
}

然后使用 JSONDecoder 解析获得的 data 即可将 json data 转为自定义模型

let dataList = try! JSONDecoder().decode(MovieDetailDic.self, from: data)