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初始化具有多个字段的结构的优雅解决方案

design-patterns swift ios

Michael Abrams · 技术社区 · 3 年前

在我的程序中,我试图找到一个优雅的解决方案来初始化用户结构。我面临的问题是,我有很多很多领域,这些领域使得初始化用户变得庞大而混乱。有一件事可能会有所帮助:

当用户首次注册到应用程序时,我希望某些字段具有默认值,如个人简历、学校、个人信息等(因为他们还没有机会填充数据)

我已经尝试过将其他结构包裹在字段中,以减少类的混乱,但这似乎仍然是一项糟糕的工作。

public struct User {
    
    //MARK: - Fields

    var email: String
    var userSettings: UserSettings
    var userProfile: UserProfile
    var uid: String
    
    
    init?(with userNode: [String: Any]) {
        
        guard let userProfile = UserProfile(userNode: userNode),
              let userSettings = UserSettings(userNode: userNode),
              let email = userNode[EMAIL] as? String,
              let uid = userNode[UID] as? String else { return nil }
        
        self.userProfile = userProfile
        self.userSettings = userSettings
        self.email = email
        self.uid = uid

    }
    
    /**
        Initalize a new user with credentials. Will initalize user with default settings and profile
     */
    init?(with credentials: AuthCredentials,
          profileDownloadUrl: [String],
          uid: String) {
        
        guard let birthday = credentials.birthday,
              let firstName = credentials.firstName,
              let lastName = credentials.lastName,
              let gender = credentials.gender,
              let preference = credentials.preference,
              let geoHash = credentials.location?.geoHash,
              let latitude = credentials.location?.latitude,
              let longitude = credentials.location?.longitude,
              let email = credentials.email else {
            return nil
        }
        
        //Create default profile
        self.userProfile = UserProfile(birthday: birthday,
                                         profilePictures: profileDownloadUrl,
                                         firstName: firstName,
                                         lastName: lastName)
        //Create default settings
        self.userSettings = UserSettings(minSeekingAge: MAX_AGE,
                                         maxSeekingAge: MIN_AGE,
                                         distanceRange: MAX_DISTANCE_RANGE,
                                         gender: gender,
                                         preference: preference,
                                         geoHash: geoHash,
                                         latitude: latitude,
                                         longitude: longitude)
        
        //Assign email
        self.email = email
        
        //Assign user id
        self.uid = uid

    }

}

建议使用什么设计模式?我已经研究了构建器的设计模式,但我个人并不喜欢,因为我仍然需要手动设置尽可能多的字段。

0 回复 | 直到 3 年前

rob mayoff 3 年前

您可以通过引入 Error 类型,以及引发该错误的辅助函数:

struct MissingField: Error { }

func missingField<R>() throws -> R { throw MissingField() }

具有 missingField ,您可以按照以下行重写每个inits:

    init?(userNode: [String: Any]) {
        do {
            userProfile = try UserProfile(userNode: userNode) ?? missingField()
            userSettings = try UserSettings(userNode: userNode) ?? missingField()
            email = try userNode[EMAIL] as? String ?? missingField()
            uid = try userNode[UID] as? String ?? missingField()
        } catch {
            return nil
        }
    }
    
    init?(
        credentials: AuthCredentials,
        profileDownloadUrl: [String],
        uid: String
    ) {
        do {
            userProfile = try UserProfile(
                birthday: credentials.birthday ?? missingField(),
                profilePictures: profileDownloadUrl,
                firstName: credentials.firstName ?? missingField(),
                lastName: credentials.lastName ?? missingField()
            )
            
            userSettings = try UserSettings(
                minSeekingAge: MAX_AGE,
                maxSeekingAge: MIN_AGE,
                distanceRange: MAX_DISTANCE_RANGE,
                gender: credentials.gender ?? missingField(),
                preference: credentials.preference ?? missingField(),
                geoHash: credentials.geoHash ?? missingField(),
                latitude: credentials.latitude ?? missingField(),
                longitude: credentials.longitude ?? missingField()
            )
            
            email = try credentials.email ?? missingField()
            self.uid = uid
        } catch {
            return nil
        }
    }