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翻譯
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# Options
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# Option
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Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not.
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Option types are very common in Rust code, as they have a number of uses:
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`Option` 類型表示一個可選的值:每個 `Option` 要麼是 `Some` 並包含一個值,要麼是 `None`,不包含任何值。
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`Option` 類型在 Rust 代碼中非常常見,因為它們有很多用途:
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- Initial values
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- Return values for functions that are not defined over their entire input range (partial functions)
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- Return value for otherwise reporting simple errors, where None is returned on error
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- Optional struct fields
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- Struct fields that can be loaned or "taken"
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- Optional function arguments
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- Nullable pointers
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- Swapping things out of difficult situations
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- 初始值
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- 函數在未定義所有輸入範圍時的返回值(部分函數)
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- 用於報告簡單錯誤的返回值,其中 `None` 表示錯誤
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- 可選的結構體字段
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- 可以被借用或“取走”的結構體字段
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- 可選的函數參數
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- 可空指針
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- 將複雜的事情變簡單
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## Further Information
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## 更多資訊
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- [Option Enum Format](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-enum-definitions)
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- [Option Module Documentation](https://doc.rust-lang.org/std/option/)
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- [Option Enum Documentation](https://doc.rust-lang.org/std/option/enum.Option.html)
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- [Option 枚舉格式](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-enum-definitions)
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- [Option 模組文檔](https://doc.rust-lang.org/std/option/)
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- [Option 枚舉文檔](https://doc.rust-lang.org/std/option/enum.Option.html)
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- [if let](https://doc.rust-lang.org/rust-by-example/flow_control/if_let.html)
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- [while let](https://doc.rust-lang.org/rust-by-example/flow_control/while_let.html)
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@ -1,18 +1,16 @@
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// options1.rs
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//
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// Execute `rustlings hint options1` or use the `hint` watch subcommand for a
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// hint.
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// 執行 `rustlings hint options1` 或使用 `hint` watch 子命令來獲取提示。
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// I AM NOT DONE
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// This function returns how much icecream there is left in the fridge.
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// If it's before 10PM, there's 5 scoops left. At 10PM, someone eats it
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// all, so there'll be no more left :(
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// 此函數返回冰箱裡剩下多少冰淇淋。
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// 如果是晚上10點之前,還剩下5勺冰淇淋。晚上10點時,有人把它全吃光了,
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// 所以不會剩下冰淇淋了 :(
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fn maybe_icecream(time_of_day: u16) -> Option<u16> {
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// We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a
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// value of 0. The Option output should gracefully handle cases where
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// time_of_day > 23.
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// TODO: Complete the function body - remember to return an Option!
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// 我們這裡使用24小時制,所以晚上10點是22,凌晨12點是0。
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// Option 輸出應該優雅地處理 time_of_day > 23 的情況。
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// TODO: 完成函數主體 - 記得返回一個 Option!
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???
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}
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@ -32,8 +30,7 @@ mod tests {
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#[test]
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fn raw_value() {
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// TODO: Fix this test. How do you get at the value contained in the
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// Option?
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// TODO: 修復此測試。您如何獲取 Option 中包含的值?
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let icecreams = maybe_icecream(12);
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assert_eq!(icecreams, 5);
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}
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@ -1,7 +1,6 @@
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// options2.rs
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//
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// Execute `rustlings hint options2` or use the `hint` watch subcommand for a
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// hint.
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// 執行 `rustlings hint options2` 或使用 `hint` watch 子命令來獲取提示。
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// I AM NOT DONE
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@ -12,7 +11,7 @@ mod tests {
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let target = "rustlings";
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let optional_target = Some(target);
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// TODO: Make this an if let statement whose value is "Some" type
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// TODO: 將此轉換為 if let 語句,其值為 "Some" 類型
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word = optional_target {
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assert_eq!(word, target);
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}
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@ -29,9 +28,8 @@ mod tests {
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let mut cursor = range;
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// TODO: make this a while let statement - remember that vector.pop also
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// adds another layer of Option<T>. You can stack `Option<T>`s into
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// while let and if let.
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// TODO: 將此轉換為 while let 語句 - 請記住,vector.pop 也會
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// 添加另一層 Option<T>。您可以將 `Option<T>` 堆疊到 while let 和 if let 中。
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integer = optional_integers.pop() {
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assert_eq!(integer, cursor);
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cursor -= 1;
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@ -1,7 +1,6 @@
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// options3.rs
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//
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// Execute `rustlings hint options3` or use the `hint` watch subcommand for a
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// hint.
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// 執行 `rustlings hint options3` 或使用 `hint` watch 子命令來獲取提示。
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// I AM NOT DONE
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@ -14,8 +13,8 @@ fn main() {
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let y: Option<Point> = Some(Point { x: 100, y: 200 });
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match y {
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Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
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_ => panic!("no match!"),
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Some(p) => println!("座標是 {},{} ", p.x, p.y),
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_ => panic!("沒有匹配!"),
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}
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y; // Fix without deleting this line.
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y; // 修復此處而不刪除此行。
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}
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