How to find if array contains object

Question

I have created a custom class called MenuItem:

import Foundation

class MenuItem {

    var title: String
    var tag: Int
    var image: UIImage

    init (title: String, tag: Int, image: UIImage) {
        self.title = title
        self.tag = tag
        self.image = image
    }

}

I am adding these objects to an array.

How can I check if an array contains a specific menu item?

This is a simplified version of what I have tried.

let menuOptionInventory = MenuItem(title: "Inventory", tag: 100, image: UIImage(imageLiteral: "871-handtruck"))
var menuOptions = [MenuItem]()
menuOptions.append(menuOptionInventory)

if (menuOptions.contains(menuOptionInventory)) {
    //does contain object
}

When I do this I get this error message:

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

You can have a look here for how to conform to equatable and/or hashable: stackoverflow.com/a/32953118/2227743 — Eric Aya
– Eric Aya, Commented Mar 9, 2016 at 15:39

Matt Le Fleur · Accepted Answer · 2016-03-09 15:55:33Z

2

Try this out:

if menuOptions.contains( { $0 === menuOptionInventory } ) {
    //does contain object
}

Edit: As JAL pointed out this does compare pointers.

So instead you could override the == operator specifically for a comparison between two MenuItem objects like this:

func == (lhs: MenuItem, rhs: MenuItem) -> Bool {
    return lhs.title == rhs.title && lhs.tag == rhs.tag && lhs.image == rhs.image
}

And then you could use the contain method closure to perform a comparison between the objects.

if menuOptions.contains( { $0 == menuOptionInventory } ) {
    //does contain object
}

edited Mar 9, 2016 at 15:55

answered Mar 9, 2016 at 15:37

Matt Le Fleur

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3 Comments

JAL Over a year ago

This will compare pointers, not object equality iirc (I didn't downvote).

Matt Le Fleur Over a year ago

Added an alternate solution, hopefully the downvoter might like it :)

Hackmodford Over a year ago

In my scenario, pointer comparison was fine. I appreciate both answers. Thanks!

JAL · Accepted Answer · 2016-03-09 15:33:40Z

1

A few issues:

contains takes in a closure. You would need to do your comparison like this:

if menuOptions.contains( { $0 == menuOptionInventory } ) {
    // do stuff
}

But now you'll get the issue that == cannot be applied to two MenuItem objects. Conform your object to Hashable and Equatable and define how two MenuItem objects are equal, or use a base class that conforms to Hashable and Equatable for you, such as NSObject.

answered Mar 9, 2016 at 15:33

JAL

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