Different ways of adding items to a dictionary with different results

Question

I'm dabbling in swift after a long time away and I've hit an issue that I can't figure out. I'm trying two different ways to add items to a dictionary and getting some different results.

I was initially adding values to a dictionary by doing:

userInfo = ["username":username]
userInfo = ["email":email]
userInfo = ["password":password]

I would then print("\(userInfo)") but it would only contain password.

I then tried switching it up to:

userInfo!["username"] = username
userInfo!["email"] = email
userInfo!["password"] = password

but this resulted in fatal error: unexpectedly found nil while unwrapping an Optional value for username

I finally switched it to the following configuration

userInfo = ["username":username]
userInfo!["email"] = email
userInfo!["password"] = password

and everything prints put. Whats up with that?

Full implementation:

nextPressed()
{
    if let userInfo:[String:String] = try registrationValidation()
    {
        print("\(userInfo)")
    }
}

func registrationValidation () throws -> [String:String]?
{
    var userInfo: [String:String]?
    var problems: [ValidationMessage] = []

    if let username = usernameField.text
    {
        let p1 = validateUsername(username)
        problems.appendContentsOf(p1)
        userInfo = ["username":username]

        //userInfo!["username"] = username
        //Above results in nil, yet lines below work?
    }

    if let email = emailField.text
    {
        let p2 = validateEmail(email)
        problems.appendContentsOf(p2)
        //userInfo = ["email":email]
        userInfo!["email"] = email
    }

    if let password = passwordField.text
    {
        let p3 = validatePassword(password)
        problems.appendContentsOf(p3)
        //userInfo = ["password":password]
        userInfo!["password"] = password
    }

    if !problems.isEmpty{
        throw ValidationError(problems:problems)
    }
    else
    {
        print("validation succeeded")
        return userInfo
    }
}

At your first attempt, you are assigning 3 different dictionaries each of them with a single key/value. What would you expect? — Leo Dabus, Apr 29 '16 at 02:54
really? I thought I was adding to the same dictionary. That makes sense. — Brosef, Apr 29 '16 at 02:56
the correct would be `userInfo = ["username":username,"email":email, "password":password]` — Leo Dabus, Apr 29 '16 at 02:58
That would work if I was adding them all at once, but I'm adding them at different times. I check username, then add it. Then do the same for email and password. — Brosef, Apr 29 '16 at 03:05
not regarding the dictionary but this might help http://stackoverflow.com/a/31954533/2303865 — Leo Dabus, Apr 29 '16 at 03:12

score 0 · Accepted Answer · answered Apr 29 '16 at 04:55

I think this would be a better way to do what you want to achieve like :

func registrationValidation () throws -> [String:String]?
{
    var userInfo = [String:String]() // **Initialize an empty dictionary**
    var problems: [ValidationMessage] = []

    if let username = usernameField.text
    {
        let p1 = validateUsername(username)
        problems.appendContentsOf(p1)
        userInfo["username"] = username
    }

    if let email = emailField.text
    {
        let p2 = validateEmail(email)
        problems.appendContentsOf(p2)
        //userInfo = ["email":email] **// This line will result in creating a new dictionary object**
        userInfo["email"] = email
    }

    if let password = passwordField.text
    {
        let p3 = validatePassword(password)
        problems.appendContentsOf(p3)
        //userInfo = ["password":password]
        userInfo["password"] = password
    }

    if !problems.isEmpty{
        throw ValidationError(problems:problems)
    }
    else
    {
        print("validation succeeded")
        return userInfo
    }
}

Different ways of adding items to a dictionary with different results

1 Answers1