160 lines
3.1 KiB
Markdown
160 lines
3.1 KiB
Markdown
---
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title: "给 Golang 开发者的 Rust 私房菜 05 流程控制"
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categories: [ "Rust" ]
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tags: [ "rust" ]
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draft: false
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slug: "rust-tutorial-05"
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date: "2025-01-05T22:57:00+0800"
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---
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## Bilibili
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{{< bilibili BV1TVrTYkETR >}}
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---
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## 条件分支
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- 使用 `if` 和 `else` 实现条件判断
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- 使用 `else if` 实现多重条件判断
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```rust
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fn main() {
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// 单个条件
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let number = 10;
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if number > 5 {
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println!("Number is greater than 5");
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} else {
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println!("Number is less than or equal to 5");
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}
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// 多个条件
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let favorite_fruit = "apple";
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if favorite_fruit == "apple" {
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println!("I like apples.");
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} else if favorite_fruit == "banana" {
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println!("I like bananas.");
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} else {
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println!("I like other fruits.");
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}
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}
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```
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在 `let` 中使用 `if`
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```rust
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fn main() {
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let number = 6;
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let result = if number % 2 == 0 { "even" } else { "odd" };
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println!("Number is {}", result);
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}
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```
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需要注意的是，`if`表达式的值取决于执行哪个代码块。这意味着 `if` 的每个分支可能产生的值必须是相同的类型，如果类型不匹配，如下例所示，我们将收到错误
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```rust
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fn main() {
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let number = 10;
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let result = if number % 2 == 0 { "even" } else { 5 };
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println!("Result is {}", result);
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}
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```
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## 循环重复
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Rust 具有三种循环： `loop` 、`while` 和 `for`
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### loop 无限循环
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使用 `loop` 关键字创建无限循环，它告诉 Rust 永远一遍又一遍地执行代码块，或者直到你明确告诉它停止为止
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```rust
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fn main() {
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let mut count = 0;
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loop {
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count += 1;
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if count > 5 {
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break;
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}
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println!("Count: {}", count);
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}
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}
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```
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`break` 允许从循环结果中返回值，传递到代码的其余部分
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```rust
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fn main() {
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let mut count = 0;
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let result = loop {
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count += 1;
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if count > 5 {
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break count * 2;
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}
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};
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println!("Result: {}", result);
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}
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```
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使用**循环标签**来中断外部循环
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```rust
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fn main() {
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'outer: loop {
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println!("Entered outer loop");
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'inner: loop {
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println!("Entered inner loop");
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break 'outer;
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}
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println!("This point will never be reached");
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}
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println!("Exited outer loop");
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}
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```
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### while 条件循环
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程序通常需要评估循环内的条件。当条件为 `true` 时，循环运行。当条件不再为 `true` 时，程序将停止循环
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```rust
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fn main() {
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let mut count = 0;
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while count < 5 {
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count += 1;
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println!("Count: {}", count);
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}
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println!("Done!");
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}
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```
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### for 遍历循环
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`for` 循环用于遍历集合，例如数组、向量、范围等
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```rust
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fn main() {
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let fruits = ["apple", "banana", "cherry"];
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for fruit in fruits {
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println!("I like {}.", fruit);
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}
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}
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```
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`for` 循环也可以用于遍历数字范围
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```rust
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fn main() {
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for number in 1..6 { // 6 不会被取到
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println!("Number: {}", number);
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}
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for number in 1..=6 { // 6 会被取到
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println!("Number: {}", number);
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}
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}
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```
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