Swift 3: Set variable in if/else statement

Question

I want to define a dynamic variable for my alert box. I'm getting a json from my server, like ok, error, username_in_use, etc etc.

let response = parseJSON["message"] as? String

if response == "username_in_use" {
    let error_msg = "Username in already use!"
} else if response == "email_in_use" {
    let error_msg = "Email address in already use!"
} else {
    let error_msg = "Unknown Error!"
}

alertView.showTitle(
    alertTitle: error_msg
)

But i'm getting this message:

Use of unresolved identifier 'error_msg'

How can I set a dynamic value for my alert title?

Thanks for help and sorry my poor english.

let error_msg: String above the if conditions and remove the let from inside the conditions brackets — Leo Dabus
– Leo Dabus, Commented Dec 11, 2016 at 17:36
Before the if ...: let error_msg = "" in if ...: error_msg = .... — shallowThought
– shallowThought, Commented Dec 11, 2016 at 17:37
Again, no need to declare it as variable as suggested in both answers. — Leo Dabus
– Leo Dabus, Commented Dec 11, 2016 at 17:45

Alexander · Accepted Answer · 2016-12-11 20:53:14Z

3

This is the perfect use case for a switch statement:

let errorMsg: String

switch response {
case "username_in_use": errorMsg = "Username in already use!"
case "email_in_use": errorMsg = "Email address in already use!"
default: errorMsg = "Unknown Error!"
}

edited Dec 11, 2016 at 20:53

answered Dec 11, 2016 at 19:30

Alexander

63.9k13 gold badges106 silver badges177 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Leo Dabus Over a year ago

You can also use let instead of var

Alexander Over a year ago

@LeoDabus Oh interesting, nice!

Marcel Steinbach · Accepted Answer · 2016-12-11 17:38:42Z

1

In your code, the scope of error_msg is limited to the blocks within the if statement. You could declare error_msg outside of the if blocks scope, e.g.

let response = parseJSON["message"] as? String
var error_msg:String

if response == "username_in_use" {
    error_msg = "Username in already use!"
} else if response == "email_in_use" {
    error_msg = "Email address in already use!"
} else {
    error_msg = "Unknown Error!"
}

alertView.showTitle(
    alertTitle: error_msg
)

answered Dec 11, 2016 at 17:38

Marcel Steinbach

1,1196 silver badges9 bronze badges

1 Comment

Alexander Over a year ago

This would be more appropriate as a Switch statement.

dfrib · Accepted Answer · 2016-12-11 20:50:07Z

If you only want to use the possibly existing (Any?) value corresponding to key "message" in the parseJSON dictionary for direct further processing/translation, you needn't necessarily store this value, but can use it inline to proceed with processing it to a valid error message. E.g., using switch statement:

var error_msg: String = "Unknown error"
switch parseJSON["message"] {
    case let val as String where val == "username_in_use": error_msg = "Username in already use!"
    case let val as String where val == "email_in_use": error_msg = "Email address in already use!"
    case _: ()
}

// ...
alertView.showTitle(
    alertTitle: error_msg
)

Or, make use of a helper dictionary to map the JSON "message" codes (values) to error messages, readily allowing use of the nil coalescing operator to supply a the default (unknown error) message:

let error_msgs = [
    "username_in_use" : "Username in already use!",
    "email_in_use"    : "Email address in already use!"]

let error_msg = error_msgs[parseJSON["message"] as? String ?? ""] ?? "Unknown Error!"

// ...
alertView.showTitle(
    alertTitle: error_msg
)

Anand · Accepted Answer · 2016-12-11 17:36:37Z

0

You should declare the let error_msg outside the if statement so that it is visible when you pass it to the alert.

   let response = parseJSON["message"] as? String

   var error_msg = ""

   if response == "username_in_use" {
       error_msg = "Username in already use!"
   } else if response == "email_in_use" {
       error_msg = "Email address in already use!"
   } else {
       error_msg = "Unknown Error!"
   }

   alertView.showTitle(alertTitle: error_msg)

answered Dec 11, 2016 at 17:36

Anand

86410 silver badges33 bronze badges

Collectives™ on Stack Overflow

Swift 3: Set variable in if/else statement

4 Answers 4

2 Comments

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related