Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

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var name: String? = nil
print(name!) // Fatal error

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var label: UILabel!
label.text = "Hello" // labelがnilの場合クラッシュ

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@IBOutlet weak var button: UIButton!
// Storyboardで接続されていない場合、アクセス時にクラッシュ
button.setTitle("Click", for: .normal)

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let data = ["name": "John"]
let age = data["age"] as! Int // キーが存在しない

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var name: String? = nil

if let unwrappedName = name {
    print(unwrappedName)
} else {
    print("Name is nil")
}

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func greet(name: String?) {
    guard let name = name else {
        print("No name provided")
        return
    }
    print("Hello, \(name)")
}

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var name: String? = nil
let displayName = name ?? "Anonymous"
print(displayName) // "Anonymous"

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var user: User? = nil
let city = user?.address?.city // nilを返す（クラッシュしない）

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let number: Int? = 5
let doubled = number.map { $0 * 2 } // Optional(10)

let nilNumber: Int? = nil
let result = nilNumber.map { $0 * 2 } // nil

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@IBOutlet weak var button: UIButton?

override func viewDidLoad() {
    super.viewDidLoad()
    button?.setTitle("Click", for: .normal)
}

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let data = ["name": "John"]
if let age = data["age"] as? Int {
    print(age)
} else {
    print("Age not found or not an Int")
}

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let data = try? JSONDecoder().decode(User.self, from: jsonData)
// エラーの場合はnilを返す

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// printでOptionalの中身を確認
print(optionalValue as Any)

// デバッガで停止
// po optionalValue

// Xcodeのデバッグナビゲータでスタックトレースを確認