Created
December 20, 2016 09:35
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可选值
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| let nickName: String? = nil | |
| let fullName: String = "John Appleseed" | |
| let informalGreeting = "Hi \(nickName ?? fullName)" |
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另一种处理可选值的方法是通过使用 ?? 操作符来提供一个默认值。如果可选值缺失的话，可以使用默认值来代替。