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
}

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.

Answer 2

Wrap your let statement in if eg:

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

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.