快速初始化结构时如何传递默认值

我已将此struct定义用于我的ErrorLogger。但是，一些参数（例如Timestamp）我想​​立即使用列出的函数。我如何传递一个默认值，而不是零的参数为：header，errorLocation，userId？为了表明如果没有其他值，将使用默认值。

想法是，如果我将一些默认值传递给这些参数，则将调用struct函数以获取这些值，否则这些值将被初始化期间用户传递的所有内容覆盖。

我也收到错误：

在初始化所有存储的属性之前自行使用

在这条线上：

self.errorLocation = getErrorLocation()

从viewController初始化结构：

let logError = LogError(header: nil, errorLocation: nil, userID: nil, description: "An error occurred while verifying if the user profile exists", errorMessage: "\(error?.localizedDescription ?? "")")

ErrorLogger中的结构：

struct LogError {
    var header: String
    var errorLocation: String
    var userID: String
    var description: String //describes the type of error
    var errorMessage: String //actual error returned by given function

    //TODO: add timestamp to lofError
    //TODO: add logEvent (enum: Error, Info) For example: data validation errors can be of event Info

    init(header: String?, errorLocation: String?, userID: String?, description: String, errorMessage: String) {
        if header != nil {
            self.header = header!
        } else {
            self.header = " ::Error::"
        }
        if errorLocation != nil  {
            self.errorLocation = errorLocation!
        } else {
            self.errorLocation = getErrorLocation()
        }
        if userID != nil {
            self.userID = userID!
        } else {
            self.userID = getUserID()
        }
        self.description = " ::description::" + description
        self.errorMessage = " ::errorMessage::" + errorMessage
    }

    func getUserID() -> String {
        var userUID: String = ""
        if Auth.auth().currentUser != nil {
            userUID = (Auth.auth().currentUser!.uid.isEmpty ? "" : Auth.auth().currentUser!.uid)
        } else {
            userUID = ""
        }
        let userUIDStr: String = " ::UserID::" + userUID
        return userUIDStr
    }

    func getErrorLocation() -> String {

        // Get class name
        let filePath: String = #file
        let components = filePath.components(separatedBy: "/")
        let className: String = components.isEmpty ? "" : components.last!

        // Get line number
        let line: Int = #line

        // Get column number
        let column: Int = #column

        // Get function name
        let funcName: String = #function

        let errorLocationStr: String  = " ::className::\(className)::lineNumber\(line)::columnNumber\(column)::funcName::\(funcName)"

        return errorLocationStr
    }

    func toString() -> String {
        let completeLogErrorMessageStr: String = header + errorLocation + userID + description + errorMessage
        return completeLogErrorMessageStr
    }
}