Swift：NSErrorを使って楽にNSAlertを表示する

はじめに

NSAlertを用いると警告のポップアップを出すことができますが、messageTextとinformativeTextを指定する方法だとアイコンが警告用になりません。

let alert = NSAlert()
alert.informativeText = "Uploaded file is broken"
alert.messageText = "Retry to upload the file."
alert.runModal()

そこで、NSErrorを使うと楽に警告用のポップアップを表示できます。

1. 普通に表示

let userInfo: [String: Any] = [
    NSLocalizedDescriptionKey:  "Uploaded file is broken",
    NSLocalizedRecoverySuggestionErrorKey: "Retry to upload the file."
]
let error = NSError(domain: "HogeDomain", code: 0, userInfo: userInfo)
let alert = NSAlert(error: error)
alert.runModal()

2. より詳細なエラー情報を付加して表示

let userInfo: [String: Any] = [
    NSLocalizedFailureErrorKey: "API Error:\t",
    NSLocalizedFailureReasonErrorKey: "duration is too short",
    NSLocalizedRecoverySuggestionErrorKey: "The video file length should be 5 seconds or more."
]
let error = NSError(domain: "HogeDomain", code: 0, userInfo: userInfo)
let alert = NSAlert(error: error)
alert.runModal()

3. さらにボタンを押した時の処理を追加する

let userInfo: [String: Any] = [
    NSLocalizedDescriptionKey:  "Uploaded file is broken",
    NSLocalizedRecoverySuggestionErrorKey: "Retry to upload the file."
]

let error = NSError(domain: "HogeDomain", code: 0, userInfo: userInfo)
let alert = NSAlert(error: error)
alert.addButton(withTitle: "Retry")
alert.addButton(withTitle: "Cancel")
let result = alert.runModal()

if result == .alertFirstButtonReturn {
    // Retry の処理
    print("Retry")
}