从Swift中的Data Model返回更多具体对象

时间:2018-01-14 15:08:05

标签: ios json struct swift3 datamodel

我正在开发一个从Firebase获取数据的应用。我要向你展示的代码工作正常,但即使作为一个新手,我知道实施应该更好。我真的无法弄清楚如何重构这个。

这是TLDR:

我创建了一个数据模型,用于设计BlogPosts。我为此使用了Struct,在初始版本中,我的所有属性都是String类型。

但是,除了标题和摘要的字符串,我的帖子还包含图像的URL和日期(发布日期)。

我希望能够从我的BlogPost对象返回更具体的对象,例如已经创建的URL或Date对象。

就像我说的,我知道我的实现很糟糕,我想学习一种更好的类型转换方式,以便我可以实现上述行为。

以下是我的BlogPost数据模型的实现:

import Foundation
import FirebaseDatabase

struct BlogPost {
    let key: String
    let title: String
    let body: String
    let summary: String
    let author: String?
    let liveSince: Date
    let featuredImageLink: URL? 
    let itemReference:DatabaseReference?

    init(snapshot: DataSnapshot) {

        let dateFormatter = DateFormatter()

        dateFormatter.dateFormat = "yyyy-mm-dd"

        key = snapshot.key
        itemReference = snapshot.ref

        if let snapshotDictionary = snapshot.value as? NSDictionary, let postTitle = snapshotDictionary["Title"] as? String {
            title = postTitle
        } else {
            title = "Cannot display Title for this item :("
        }

        if let snapshotDictionary = snapshot.value as? NSDictionary, let postBody = snapshotDictionary["Body"] as? String {
            body = postBody
        } else {

            body = "Cannot display Body for this item :("
        }
        if let snapshotDictionary = snapshot.value as? NSDictionary, let postSummary = snapshotDictionary["Summary"] as? String {
            summary = postSummary
        } else {
            summary = "Due to some weird error, the Summary for this item cannot be displayed. Insert more coffee and Pizza in developer"
        }

        if let snapshotDictionary = snapshot.value as? NSDictionary, let postAuthor = snapshotDictionary["Author"] as? String {
            author = postAuthor
        } else {
            author = "Nobody wrote this :("
        }
        if let snapshotDictionary = snapshot.value as? NSDictionary, let postImageLink = snapshotDictionary["FeaturedImage"] as? String {

            featuredImageLink = URL(string: postImageLink)!

        } else {

            featuredImageLink = URL(string:"https://someimagelink")!
        }

        if let snapshotDictionary = snapshot.value as? NSDictionary, let liveDate = snapshotDictionary["LiveSince"] as? String {

            if let live = dateFormatter.date(from: liveDate)  {

                liveSince = live

            } else {

                liveSince = dateFormatter.date(from: "1990-06-26")!

            }

        } else {

                liveSince = dateFormatter.date(from: "1990-06-26")!
        }

    }

}

任何建设性的反馈都非常受欢迎,因为我真的想要了解如何正确地做到这一点,或者首先是否有意义这样做!

非常感谢你提前回复!

1 个答案:

答案 0 :(得分:1)

我有一些建议。看起来你继续使用条件绑定来展开snapshsot.value,同时将其作为NSDictionary进行转换。由于展开此值是解开其他值的先决条件,为什么不使用guard语句来解包呢?在guard语句中,您可以默认初始化结构中的所有属性。或者,如果您不坚持默认初始化属性,则可以使用可用的初始化程序,并在guard语句中返回nil。

guard let snapshotDictionary = snapshot.value as? NSDictionary else { 
    title = "Cannot display Title for this item :("
    body = "Cannot display Body for this item :("
    summary = "Due to some weird error, the Summary for this item cannot be 
    displayed. Insert more coffee and Pizza in developer"
    ...
    ...
}