⁉️Optional

🔴 主題

• optional binding - if let, while let, guard let ...

• optional chaining - 🚧 施工中

• nil coalescing - a ?? b.

• compare with Optional

💾 程式

func thrower(shouldThrow: Bool) throws {
    if shouldThrow {
        throw TestError.someError
    }
}

// ⭐️ we have to explicitly declare the type of the variable
//    to avoid getting a warning from the compiler for attempting
//    to capture a return value that we have not explicitly declared.
var result: Void? = try? thrower(shouldThrow: false)

print(result == nil)    // false

result = try? thrower(shouldThrow: true)
print(result == nil)    // true

📘 手冊

• Swift ⟩ Standard Library ⟩ Numbers & Basic Values ⟩ Optional

• Swift Language Guide ⟩ Optionals

⭐️ 重點

Interestingly, in Swift, there is no such thing as a function with no return type. Functions with no return type implicitly have a return type of Void and a special return value of (), which is an empty tuple. An optional can be used to wrap any Swift type, including Void.

We can use this to extend our above example to a function without an explicit return type. 👉 What Are Swift Optionals and How They Are Used

📗 參考

• What Are Swift Optionals and How They Are Used - KHAWER KHALIQ ⭐️