CODEWITHSUNDEEP
arraysswiftswift2indexof
Black Sheep
Black Sheep

Reputation: 1675

indexOf of AnyObject array not working with Strings

So I'm having the following code in a playgroung 

var array: [AnyObject] = ["", "2", "3"]

let index = array.indexOf("")

And XCode is marking a compiler error

Cannot convert value of type 'String' to expected argument type '@noescape (AnyObject) throws -> Bool'

So my question is how do I get the indexOf an element in an Array in of AnyObjects?

Upvotes: 4

Views: 2684

Answers (4)

Kesong Xie
Kesong Xie

Reputation: 1396

In more general cases, collectionType.indexOf will work when the object inside an array conforms to Equatable protocol. Since Swift String has already conformed to Equatable, then casts AnyObject to String will remove the error.

How to use indexOf on collection type custom class ? Swift 2.3

class Student{
   let studentId: Int
   let name: String
   init(studentId: Int, name: String){
     self.studentId = studentId
     self.name = name
   }
}

//notice you should implement this on a global scope
extension Student: Equatable{
}

func ==(lhs: Student, rhs: Student) -> Bool {
    return lhs.studentId == rhs.studentId //the indexOf will compare the elements based on this
}


func !=(lhs: Student, rhs: Student) -> Bool {
    return !(lhs == rhs)
}

Now you can use it like this

let john = Student(1, "John")
let kate = Student(2, "Kate")
let students: [Student] = [john, kate] 
print(students.indexOf(John)) //0
print(students.indexOf(Kate)) //1

Upvotes: 0

Lukas
Lukas

Reputation: 3433

You can also cast to [String] if you're sure it will cast safely 

jvar array: [AnyObject] = ["", "2", "3"]
let index = (array as! [String]).indexOf("")

Upvotes: 6

Kametrixom
Kametrixom

Reputation: 14973

You should never use AnyObject for a placeholder for any type, use Any instead. Reason: AnyObject only works with classes, Swift uses a lot of structs though (Array, Int, String, etc.). Your code actually uses NSStrings instead of Swifts native String type because AnyObject wants a class (NSString is a class).

Upvotes: 0

Marius Fanu
Marius Fanu

Reputation: 6669

Try this

var array = ["", "2", "3"]
let index = array.indexOf("")

or you can use the NSArray method:

var array: [AnyObject] = ["", "2", "3"]
let index = (array as NSArray).indexOfObject("")

Upvotes: 3

Related Questions