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@ -1,21 +1,21 @@
# Options
# Option
Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not.
Option types are very common in Rust code, as they have a number of uses:
`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。
`Option` 類型在 Rust 代碼中非常常見,因為它們有很多用途:
- Initial values
- Return values for functions that are not defined over their entire input range (partial functions)
- Return value for otherwise reporting simple errors, where None is returned on error
- Optional struct fields
- Struct fields that can be loaned or "taken"
- Optional function arguments
- Nullable pointers
- Swapping things out of difficult situations
- 初始值
- 函數在未定義所有輸入範圍時的返回值(部分函數)
- 用於報告簡單錯誤的返回值,其中 `None` 表示錯誤
- 可選的結構體字段
- 可以被借用或“取走”的結構體字段
- 可選的函數參數
- 可空指針
- 將複雜的事情變簡單
## Further Information
## 更多資訊
- [Option Enum Format](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-enum-definitions)
- [Option Module Documentation](https://doc.rust-lang.org/std/option/)
- [Option Enum Documentation](https://doc.rust-lang.org/std/option/enum.Option.html)
- [Option 枚舉格式](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-enum-definitions)
- [Option 模組文檔](https://doc.rust-lang.org/std/option/)
- [Option 枚舉文檔](https://doc.rust-lang.org/std/option/enum.Option.html)
- [if let](https://doc.rust-lang.org/rust-by-example/flow_control/if_let.html)
- [while let](https://doc.rust-lang.org/rust-by-example/flow_control/while_let.html)

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@ -1,18 +1,16 @@
// options1.rs
//
// Execute `rustlings hint options1` or use the `hint` watch subcommand for a
// hint.
// 執行 `rustlings hint options1` 或使用 `hint` watch 子命令來獲取提示。
// I AM NOT DONE
// This function returns how much icecream there is left in the fridge.
// If it's before 10PM, there's 5 scoops left. At 10PM, someone eats it
// all, so there'll be no more left :(
// 此函數返回冰箱裡剩下多少冰淇淋。
// 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
// 所以不會剩下冰淇淋了 :(
fn maybe_icecream(time_of_day: u16) -> Option<u16> {
// We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a
// value of 0. The Option output should gracefully handle cases where
// time_of_day > 23.
// TODO: Complete the function body - remember to return an Option!
// 我們這裡使用24小時制所以晚上10點是22凌晨12點是0。
// Option 輸出應該優雅地處理 time_of_day > 23 的情況。
// TODO: 完成函數主體 - 記得返回一個 Option
???
}
@ -32,8 +30,7 @@ mod tests {
#[test]
fn raw_value() {
// TODO: Fix this test. How do you get at the value contained in the
// Option?
// TODO: 修復此測試。您如何獲取 Option 中包含的值?
let icecreams = maybe_icecream(12);
assert_eq!(icecreams, 5);
}

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@ -1,7 +1,6 @@
// options2.rs
//
// Execute `rustlings hint options2` or use the `hint` watch subcommand for a
// hint.
// 執行 `rustlings hint options2` 或使用 `hint` watch 子命令來獲取提示。
// I AM NOT DONE
@ -12,7 +11,7 @@ mod tests {
let target = "rustlings";
let optional_target = Some(target);
// TODO: Make this an if let statement whose value is "Some" type
// TODO: 將此轉換為 if let 語句,其值為 "Some" 類型
word = optional_target {
assert_eq!(word, target);
}
@ -29,9 +28,8 @@ mod tests {
let mut cursor = range;
// TODO: make this a while let statement - remember that vector.pop also
// adds another layer of Option<T>. You can stack `Option<T>`s into
// while let and if let.
// TODO: 將此轉換為 while let 語句 - 請記住vector.pop 也會
// 添加另一層 Option<T>。您可以將 `Option<T>` 堆疊到 while let 和 if let 中。
integer = optional_integers.pop() {
assert_eq!(integer, cursor);
cursor -= 1;

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@ -1,7 +1,6 @@
// options3.rs
//
// Execute `rustlings hint options3` or use the `hint` watch subcommand for a
// hint.
// 執行 `rustlings hint options3` 或使用 `hint` watch 子命令來獲取提示。
// I AM NOT DONE
@ -14,8 +13,8 @@ fn main() {
let y: Option<Point> = Some(Point { x: 100, y: 200 });
match y {
Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
_ => panic!("no match!"),
Some(p) => println!("座標是 {},{} ", p.x, p.y),
_ => panic!("沒有匹配!"),
}
y; // Fix without deleting this line.
y; // 修復此處而不刪除此行。
}