nil value after variable assignment - ios

Question

I have a VC that contains of textField and button. I have a simple task to pass textField text data to my model entity. However, while I want to assign textField data to entity data, my data remains nil.
I can't understand what have caused such problem
class InputTextViewController: UIViewController {
#IBOutlet weak var messageTextField: UITextField!
//I receive user from parent VC by segue
var userSendMessageTo: User!
var tableView: UITableView?
var message: Message { return Message(userSendMessageTo) }
// initialising object of my entity class
override func viewDidLoad() {
super.viewDidLoad()
print(userSendMessageTo.name)
//name is right
}
func createMessage() {
message.messageText = messageTextField.text
message.messageTime = Date()
print(message.messageText) //nil
print(message.messageTime) //nil
}
#IBAction func sendMessge(_ sender: Any) {
createMessage()
userSendMessageTo.mesaageHistory.append(message)
print(userSendMessageTo.mesaageHistory[0].messageText) //nil
}
My model
class Message {
var messageText: String?
var messageTime: Date?
var messageInage: UIImage?
var user: User
init(_ user: User) {
self.user = user
}
}
class User {
let name: String
var mesaageHistory = [Message]()
init(name: String) {
self.name = name
}
}

Answer 1

The construct var message: Message { return Message(userSendMessageTo) } returns a new Message object every time it's called.
Therefore you are creating a message object, assigning text to it, then throwing it away. Then you create a second message object, assign a date to it and throw it away. Then you create a third message object and check its text (which is nil) and then you create a fourth message object and check its date, which is also nil.
Try this instead:
class InputTextViewController: UIViewController {
#IBOutlet weak var messageTextField: UITextField!
var userSendMessageTo: User!
var tableView: UITableView?
var message: Message?
func createMessage() {
message = Message()
message!.messageText = messageTextField.text
message!.messageTime = Date()
print(message!.messageText) //won't be nil
print(message!.messageTime) //won't be nil
}
}

Answer 2

You have declared message as a computed variable. This means that each time you reference message you are actually executing the following block of code:
Message(userSendMessageTo)
In other words, each reference to message creates a new instance of Message.
message.messageText = messageTextField.text - Creates a new instance of Message
message.messageTime = Date() - creates a new instance of Message
print(message.messageTime) - create a new instance of Message, and its messageTime property is nil
There is no need to use a property here; your createMessage function should return the new Message:
func createMessage(withText text: text) -> Message {
let message = Message(userSendMessageTo)
message.messageText = text
message.messageTime = Date()
return message
}
#IBAction func sendMessge(_ sender: Any) {
let message = self.createMessage(withText: messageTextField.text)
userSendMessageTo.mesaageHistory.append(message)
print(userSendMessageTo.mesaageHistory[0].messageText)
}
To be honest, if you create a proper initialiser for Message you could get rid of the createMessage function altogether:
class Message {
var messageText: String
var messageTime: Date
var messageInage: UIImage?
var user: User
class Message {
var messageText: String
var messageTime: Date
var messageInage: UIImage?
var user: User
init(_ user: User, text: String = "", date: Date = Date()) {
self.user = user
self.messageTime = date
self.messageText = text
}
}
Then your action method simply becomes:
#IBAction func sendMessge(_ sender: Any) {
let message = Message(userSendMessageTo, text: messageTextField.text, date:Date())
userSendMessageTo.mesaageHistory.append(message)
print(userSendMessageTo.mesaageHistory[0].messageText)
}