Question 68016 in IOS Swift Question posted in
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what can I pass [SomeType] to "paramName: SomeType = []" swift? – Ios swift

I’m pretty new to swift, trying to get authorization from user.

to request multiple auth at once, I gathered multiple options as array, and trying to request.

let variableArray = [UNAuthorizationOptions.badge, UNAuthorizationOptions.alert]
// error: Cannot convert value of type '[UNAuthorizationOptions]' to expected argument type 'UNAuthorizationOptions'
try! await UNUserNotificationCenter.current().requestAuthorization(options: variableArray)


//these works.        
try! await UNUserNotificationCenter.current().requestAuthorization(options: [.badge, .alert])
try! await UNUserNotificationCenter.current().requestAuthorization(options: .badge)

so I checked requestAuthorization, and found this:

open func requestAuthorization(options: UNAuthorizationOptions = []) async throws -> Bool

I think it takes both UNAuthorizationOptions and [UNAuthorizationOptions] but compiler says

"hey, you are trying to pass [UNAuthorizationOptions] but I need
UNAuthorizationOptions!"

how can I append variableArray above code to requestAuthorization?

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2

Answers


  1. 0

    You need to explicitly specify the type of your variableArray as UNAuthorizationOptions. Replace variableArray with:

    let variableArray: UNAuthorizationOptions = [UNAuthorizationOptions.badge, UNAuthorizationOptions.alert]
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  2. 0

    This is because UNAuthorizationOptions conforms to the protocol OptionSet and an OptionSet can be initialised using an array literal, that is […] which is something different than your variableArray which is an Array object.

    So this is why you can do both

    try! await UNUserNotificationCenter.current().requestAuthorization(options: [.badge, .alert])
try! await UNUserNotificationCenter.current().requestAuthorization(options: .badge)

    because one takes an UNAuthorizationOptions and the other one an OptionSet of UNAuthorizationOptions

    You will find that this is quite a common pattern in swift when passing options or similar to functions in UIKit, AppKit, Foundation etc

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