Cannot call value of non-function type 'String'

Question

I'm trying to pass the ILTItem variable into my ILTViewController, triggered by AppDelegate.swift when the user launches my app via a deeplink.

The code I have errors with:

Cannot call value of non-function type 'String'

on the line where I define ilt.

Here's the code I have at the moment:

let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
var ilt = ILT(homeworkID: 1234, title: "History ILT", subject: "History", teacher: "Miss A Smith", teacherCode: "asmith", studentID: 12345, description: "Description....", due: 1450137600, status: "In Progress", hasAttachments: true)
var newVC = ILTViewController()
newVC.ILTitem = ilt
appDelegate.window?.addSubview(newVC.view)

Why could this be? In my ILTViewController class I have:

class ILTViewController: UIViewController {
  // accept the incoming ILT struct
  var ILTitem: ILT!

IlT Struct Declaration:

struct ILT {
    let homeworkID: Int
    let title: String
    let subject: String
    let teacher: String
    let teacherCode: String
    let studentID: Int
    let description: String
    let due: Double
    let status: String
    let hasAttachments: Bool
}

Unpaged

Post your ILT class declaration – Accommodative

@Accommodative I have added it – Unpaged

Your code works fine: swiftstub.com/580271845 . You've probably declared a String variable named ILT somewhere else and that's why it fails. – Accommodative

@Accommodative That's not the issue, as when I combine it down to newVC.ILTItem = ILT(homeworkID: 1234, title: "History ILT", subject: "History", teacher: "Miss A Smith", teacherCode: "asmith", studentID: 12345, description: "Description....", due: 1450137600, status: "In Progress", hasAttachments: true) it still fails with the same message. – Unpaged

What I was saying is that you redeclared ILT (uppercase), not ilt (lowercase). The error is telling you that you are trying to call a String instead of a method (struct constructor in your case). And, as you can check in the link I provided, the error is elsewhere in your code, because the code you posted works fine. – Accommodative

@Accommodative Oh, I see. Didn't realise variables and methods can clash names, I've found the problem now. Thank you very much :) – Unpaged

Cool, I'll convert the comment to an answer so others can benefit from it. – Accommodative

Answer 1

The error is telling you that you are trying to call a String instead of a method (struct constructor in your case). You've probably declared a String variable named ILT (uppercase) somewhere else and that's why it fails.

Your posted code works fine so the error must be somewhere else in your code.

Accommodative

Thanks. Related but slightly separate issue to the question - my ILTViewController: UIViewController class does not receive the new variable - printing ILTItem.title returns null. Any idea why? – Unpaged

I recommend you to open a new question with the relevant code and preferably a self contained sample project reproducing the issue. – Accommodative

Happened to me when accidentally calling a KRProgressHUD.show()() (double parenthesis accident) – Filberte

Answer 2

Wrap your let statement in if eg:

if let xxx = yyy {
   ... do something
}

Enid

Answer 3

Works:

let works = ["foo", "bar"].first(where: { ($0 == "foo") } )
let works = ["foo", "bar"].first(where: { (_ in true) } )

Fails:

let fails = ["foo", "bar"].first(where: { (true) } )

// Cannot call value of a non-function type 'String?'

You must be sure to use the parameter ($0 or _ in) in the closure expression.

Use _ in or $0 to discard or reference the parameter. You cannot simple move directly into the closure body and return true or you will receive this (extremely unhelpful) error.

Nyaya

Answer 4

Had a similar issue in this code

array.first { $0 == item }

The problem was with $0 not conforming to Equatable protocol. In my case it conformed to NSObjectProtocol and simple pointer comparison was enough, so I fixed the issue with

array.first { $0 === item }

Gerald

Answer 5

So I had a problem with a similar error message. I am writing a structure to handle Scalars for my library and needed a square root. Error was

Cannot call value of non-function type 'Vsip.Scalar'

when calling sqrt. Fixed it by explicitly calling sqrt as shown below. Hope this helps.

public var sqrt: Scalar {
        switch self.type {
        case .f:
            return Scalar(sqrtf(self.realf))
        case .d:
            let x = Foundation.sqrt(self.reald)
            return Scalar(x)
        case .cf:
            return Scalar(vsip_csqrt_f(self.vsip_cf))
        case .cd:
            return Scalar(vsip_csqrt_d(self.vsip_cd))
        default:
            precondition(false, "sqrt not supported for type \(self.type)")
        }
    }

Violetavioletta

Answer 6

In messing around with Swift's various closure syntax types + autocomplete I often find myself in a mess of variables, return types, and using too few or too many sets of () or {}

I ended up with something like:

filenames.first(where: { $0 == filename } ) {

}

Which was giving the error

Cannot call value of non-function type

Solution was to remove the trailing { }, which is not correct in this form.

Should just be filenames.first(where: { $0 == filename } )

Check that you have not incorrectly applied a set of braces to the end of your non-function, etc., or some other hard to spot error in your current chosen Swift closure syntax.

Nyaya

Answer 7

Check if you haven't missed ? for optionals.

That error can be shown for a different issue in a heavy-loaded schemes, like when I forget to mark optional.

services.first(where: { $0.category?.id == categoryID })

Augsburg