Remove a custom object from an array (Swift)

Question

I have an array called remindersArray that contains a custom object called Reminder (each Reminder object has title and identifier).

Inside Reminder I have a static fun called removeReminderWithIdentifier that should find the reminder and delete it from the array.

I've tried to do it like this:

static func removeReminderWithIdentifier(reminderIdentifier: String) {
    for currentReminder in Reminder.remindersArray {
        if currentReminder.identifier == reminderIdentifier {
            Reminder.remindersArray.removeAtIndex(Reminder.remindersArray.indexOf(currentReminder)) //Compile error
        }
    }
}

but it gives me this compile error:

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

Any idea how can I remove that object with this identifier from the array?

Thanks!

I ran into the exact same problem!

SilverWolf
– SilverWolf

2017-10-09 22:01:39 +00:00
Commented Oct 9, 2017 at 22:01 — SilverWolf
– SilverWolf, Commented Oct 9, 2017 at 22:01

OOPer · Accepted Answer · 2016-09-03 10:32:35Z

See the header of two indexOf(_:) methods for CollectionType:

extension CollectionType where Generator.Element : Equatable {
    /// Returns the first index where `value` appears in `self` or `nil` if
    /// `value` is not found.
    ///
    /// - Complexity: O(`self.count`).
    @warn_unused_result
    public func indexOf(element: Self.Generator.Element) -> Self.Index?
}

extension CollectionType {
    /// Returns the first index where `predicate` returns `true` for the
    /// corresponding value, or `nil` if such value is not found.
    ///
    /// - Complexity: O(`self.count`).
    @warn_unused_result
    public func indexOf(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Index?
}

If you want to use the first indexOf(_:) (which you are trying in your code), the element type needs to be Equatable. When your Reminder class does not conform to Equatable, Swift ignores the first indexOf(_:), so the second can be the only candidate, having @noescape (Self.Generator.Element) throws -> Bool as its only argument. In your case Self.Generator.Element is Reminder.

So, one way to avoid this error is making your Reminder conform to Equatable.

extension Reminder: Equatable {}
func == (lhs: Reminder, rhs: Reminder) -> Bool {
    return lhs.identifier == rhs.identifier /* && ... you may need more complex condition. */
    /* return lhs === rhs //or simple use `===`. */
}

But you have some options to do it:

If your reminderArray contains just one element for each unique identifier, you can write something like this, without making your Reminder Equatable:

static func removeReminderWithIdentifier(reminderIdentifier: String) {
    if let index = Reminder.remindersArray.indexOf({$0.identifier == reminderIdentifier}) {
        Reminder.remindersArray.removeAtIndex(index)
    }
}

If your remindersArray may contain multiple Reminder instances having the same identifier, this should work:

static func removeReminderWithIdentifier3(reminderIdentifier: String) {
    Reminder.remindersArray = Reminder.remindersArray.filter{$0.identifier != reminderIdentifier}
}

Choose one (or more?) and make it a try.

Vince O'Sullivan · Accepted Answer · 2016-09-03 11:42:15Z

1

You could filter out the unwanted reminders:

static func removeReminderWithIdentifier(reminderIdentifier: String) {
    Reminder.remindersArray = Reminder.remindersArray.filter { $0.identifier != reminderIdentifier }
}

Alternately:

func removeReminderWithIdentifier(reminderIdentifier: String) {
    remindersArray = remindersArray.filter { $0.identifier != reminderIdentifier }
}

And in the latest swift naming style...:

func removeReminders(with identifier: String) {
    remindersArray = remindersArray.filter { $0.identifier != identifier }
}

edited Sep 3, 2016 at 11:42

answered Sep 3, 2016 at 10:51

Vince O'Sullivan

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2 Comments

FS.O6 Over a year ago

Cannot call value of non-function type '[Reminder]'

Vince O'Sullivan Over a year ago

Without seeing your code I am guessing... Remove the static prefix and also the two references to Reminder in the func. I've updated the answer accordingly.

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