We need only one thing in order to delete an item from the Keychain: a CFDictionary with attributes describing the items to be deleted. Any items that match the query dictionary will be deleted permanently, so if you are only intending to delete a single item be sure to be specific with your query. As always, we can use an NSDictionary in Objective-C or in Swift we can use a Dictionary and then cast to CFDictionary.

A query dictionary, in this context exclusively includes a class key to describe what the item is and attributes to describe information about the item. Inclusion of search restrictions such as kSecMatchCaseInsensitive is not allowed.

Swift

var dict = [String : AnyObject]()
dict[kSecClass as String] = kSecClassGenericPassword
// Label
dict[kSecAttrLabel as String] = "com.me.myapp.myaccountpassword" as CFString
// Username
dict[kSecAttrAccount as String] = "My Name" as CFString

And now we can simply remove it:

Swift

let status = SecItemDelete(dict as CFDictionary)

SecItemDelete returns an OSStatus. Result codes are described here.