concatenate in swift: Binary operator '+' cannot be applied to operands of type 'String' and 'AnyObject'

Question

I get the error in Swift and don't understand it when I do this:

if(currentUser["employer"] as! Bool == false) { print("employer is false: "+currentUser["employer"] as! Bool) }

But I can do (Its not actually printing anything though, maybe another problem):

if(currentUser["employer"] as! Bool == false) { print(currentUser["employer"]) }

Results in error:

Binary operator '+' cannot be applied to operands of type 'String' and 'AnyObject'

Similarly:

                let currentUser = PFUser.currentUser()!
                let isEmployer = currentUser["employer"]
                print("isEmployer: \(isEmployer)")
                print(currentUser["employer"])

But these two don't work:

                print("employer: "+currentUser["employer"])
                print("employer: \(currentUser["employer"])")

I also happen to be using Parse to get data, and not sure if that is the right way either.

Solution

The error message might be misleading in the first example

if currentUser["employer"] as! Bool == false { 
 print("employer is false: "+currentUser["employer"] as! Bool) 
}

In this case, the error message is supposed to be

binary operator '+' cannot be applied to operands of type 'String' and 'Bool'

because currentUser["employer"] as! Bool is a non-optional Bool and cannot be implicitly cast to String

Those examples

print("employer: "+currentUser["employer"])
print("employer: \(currentUser["employer"])")

don't work because

• In the first line, currentUser["employer"] without any typecast is an optional AnyObject (aka unspecified) which doesn't know a + operator.
• In the second line, the string literal "employer" within the String interpolated expression causes a syntax error (which is fixed in Xcode 7.1 beta 2).

---

Edit:

This syntax is the usual way.

let isEmployer = currentUser["employer"]
print("isEmployer: \(isEmployer)")

Or alternatively, you can write

print("employer is " + String(currentUser["employer"] as! Bool))

Comments

[Arthur Gevorkyan]

could you specify the error?

[Tilo Delau]

The error was in the title, exactly as is: Binary operator '+' cannot be applied to operands of type 'String' and 'AnyObject'

[Tilo Delau]

ok. So last example will be a feature added in the future, but the first two are casting errors and is just something that can't be done with swift?

[vadian]

It can be. Your code let isEmployer = currentUser["employer"] print("isEmployer: \(isEmployer)") is the proper way. Or you can write print("employer is " + String(currentUser["employer"] as! Bool))

[Tilo Delau]

print("employer is " + String(currentUser["employer"] as! Bool)) is what I was looking for...which is too tedious! But now I clearly understand what is going on. So I should cast it myself in a variable first. With simple stuff, I've gotten away with using +. Thank you.