Cannot convert value of type ‘Meme!’ to expected argument type ‘@noescape (Meme) throws -> Bool’

by

The error message is misleading. What you actually need is to provide the compiler a way to compare two Meme instances and decide upon which criteria those instances are equal.

Let’s say you want two instances having the same name property to be treated as equal.

We make the struct conform to Equatable and we also create an == operator that compares two structs by their name property:

struct Meme:Equatable {
    var name:String!
}

func ==(lhs: Meme, rhs: Meme) -> Bool {
    return lhs.name == rhs.name
}

Now we can use indexOf with a Meme instance:

let doge = Meme(name: "doge")

let lolcat = Meme(name: "lolcat")

let memes = [lolcat, doge]

if let dogeIndex = memes.indexOf(doge) {
    print(dogeIndex)  // 1
}

If you wanted to compare two instances not by their name property but by their uniqueness, then you would have to make the struct conform to Hashable and use a unique hashValue property returning an Int:

struct Meme:Hashable {
    var name:String!
    var hashValue: Int {
        return self.name.hashValue
    }
    init(name: String) {
        self.name = name
    }
}

func ==(lhs: Meme, rhs: Meme) -> Bool {
    return lhs.hashValue == rhs.hashValue
}

let doge = Meme(name: "doge")

let lolcat = Meme(name: "lolcat")

let memes = [lolcat, doge]

if let dogeIndex = memes.indexOf(doge) {
    print(dogeIndex)  // 1
}

In this example the hashValue is made from self.name, so two different instances of Meme with a same name property will be considered equal. If you don’t want that, use another source for the hash value.

Note: in Swift 3, indexOf has become index(of:), so for this example we would change memes.indexOf(doge) to memes.index(of: doge).

More Related Contents:

  1. how to check if there is any string from index 0 to 5 in an array of type Any [closed]
  2. remove an index number from array
  3. How to find index of list item in Swift?
  4. Get random elements from array in Swift
  5. Swift: Creating an Array with a Default Value of distinct object instances
  6. Two-dimensional array in Swift
  7. Why isn’t [SomeStruct] convertible to [Any]?
  8. How can I extend typed Arrays in Swift?
  9. Making my function calculate average of array Swift
  10. Converting a C char array to a String
  11. Sorting a Swift array by ordering from another array
  12. Confused about Swift Array Declarations
  13. Finding sum of elements in Swift array
  14. Swift 3.0: compiler error when calling global func min(T,T) in Array or Dictionary extension
  15. Count the occurences a particular integer has in an array [duplicate]
  16. Find min / max value in Swift Array
  17. type any? has no subscript members
  18. How to split a string by new lines in Swift
  19. Creating an extension to filter nils from an Array in Swift
  20. Convert bytes/UInt8 array to Int in Swift
  21. Compare arrays in swift
  22. Swift: What’s the best way to pair up elements of an Array
  23. How can I decode a JSON response with an unknown key in Swift?
  24. Multidimensional arrays in Swift
  25. Extending Array to check if it is sorted in Swift?
  26. How to merge two arrays in Swift
  27. What does $0 and $1 mean in Swift Closures?
  28. How can I run through three separate arrays in the same for loop?
  29. Operation on an array of structs implementing Equatable
  30. How to convert UInt8 byte array to string in Swift

Leave a Comment