[易学易懂系列|rustlang语言|零基础|快速入门|（9）]

有意思的基础知识

Control Flows

我们今天再来看看流程控制。

条件控制 if-else if -else:

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1/ Simplest Example  

2let team_size = 7;  

3if team_size < 5 {  

4   println!("Small");  

5} else if team_size < 10 {  

6   println!("Medium");  

7} else {  

8   println!("Large");  

9}  

10​  

11// partially refactored code  

12let team_size = 7;  

13let team_size_in_text;  

14if team_size < 5 {  

15   team_size_in_text = "Small";  

16} else if team_size < 10 {  

17   team_size_in_text = "Medium";  

18} else {  

19   team_size_in_text = "Large";  

20}  

21println!("Current team size : {}", team_size_in_text);  

22​  

23//optimistic code  

24let team_size = 7;  

25let team_size_in_text = if team_size < 5 {  

26   "Small" //⭐️no ;  

27} else if team_size < 10 {  

28   "Medium"  

29} else {  

30   "Large"  

31};  

32println!("Current team size : {}", team_size_in_text);  

33​  

34​  

35let is_below_eighteen = if team_size < 18 { true } else { false };

36

模式匹配 match ：

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1let tshirt_width = 20;  

2let tshirt_size = match tshirt_width {  

3   16 => "S", // check 16  

4   17 | 18 => "M", // check 17 and 18  

5   19 ... 21 => "L", // check from 19 to 21 (19,20,21)  

6   22 => "XL",  

7   _ => "Not Available",  

8};  

9println!("{}", tshirt_size); // L  

10​  

11​  

12let is_allowed = false;  

13let list_type = match is_allowed {  

14   true => "Full",  

15   false => "Restricted"  

16   // no default/ _ condition can be skipped  

17   // Because data type of is_allowed is boolean and all possibilities checked on conditions  

18};  

19println!("{}", list_type); // Restricted  

20​  

21​  

22let marks_paper_a: u8 = 25;  

23let marks_paper_b: u8 = 30;  

24let output = match (marks_paper_a, marks_paper_b) {  

25   (50, 50) => "Full marks for both papers",  

26   (50, _) => "Full marks for paper A",  

27   (_, 50) => "Full marks for paper B",  

28   (x, y) if x > 25 && y > 25 => "Good",  

29   (_, _) => "Work hard"  

30};  

31println!("{}", output); // Work hard

32

while:

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1let mut a = 1;  

2while a <= 10 {  

3   println!("Current value : {}", a);  

4   a += 1; //no ++ or -- on Rust  

5}  

6​  

7// Usage of break and continue  

8let mut b = 0;  

9while b < 5 {  

10   if b == 0 {  

11       println!("Skip value : {}", b);  

12       b += 1;  

13       continue;  

14   } else if b == 2 {  

15       println!("Break At : {}", b);  

16       break;  

17   }  

18   println!("Current value : {}", b);  

19   b += 1;  

20}  

21​  

22// Outer break  

23let mut c1 = 1;  

24'outer_while: while c1 < 6 { //set label outer_while  

25   let mut c2 = 1;  

26   'inner_while: while c2 < 6 {  

27       println!("Current Value : [{}][{}]", c1, c2);  

28       if c1 == 2 && c2 == 2 { break 'outer_while; } //kill outer_while  

29       c2 += 1;  

30   }  

31   c1 += 1;  

32}

33

loop

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1loop {  

2   println!("Loop forever!");  

3}  

4​  

5// Usage of break and continue  

6let mut a = 0;  

7loop {  

8   if a == 0 {  

9       println!("Skip Value : {}", a);  

10       a += 1;  

11       continue;  

12   } else if a == 2 {  

13       println!("Break At : {}", a);  

14       break;  

15   }  

16   println!("Current Value : {}", a);  

17   a += 1;  

18}  

19​  

20// Outer break  

21let mut b1 = 1;  

22'outer_loop: loop { //set label outer_loop  

23 let mut b2 = 1;  

24'inner_loop: loop {  

25   println!("Current Value : [{}][{}]", b1, b2);  

26   if b1 == 2 && b2 == 2 {  

27       break 'outer_loop; // kill outer_loop  

28   } else if b2 == 5 {  

29       break;  

30   }  

31   b2 += 1;  

32}  

33 b1 += 1;  

34}

35

for

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1for a in 0..10 { //(a = o; a <10; a++) // 0 to 10(exclusive)  

2 println!("Current value : {}", a);  

3}  

4​  

5// Usage of break and continue  

6for b in 0..6 {  

7 if b == 0 {  

8   println!("Skip Value : {}", b);  

9   continue;  

10} else if b == 2 {  

11   println!("Break At : {}", b);  

12   break;  

13}  

14 println!("Current value : {}", b);  

15}  

16​  

17// Outer break  

18'outer_for: for c1 in 1..6 { //set label outer_for  

19'inner_for: for c2 in 1..6 {  

20   println!("Current Value : [{}][{}]", c1, c2);  

21   if c1 == 2 && c2 == 2 { break 'outer_for; } //kill outer_for  

22}  

23}  

24​  

25​  

26// Working with arrays/vectors  

27let group : [&str; 4] = ["Mark", "Larry", "Bill", "Steve"];  

28​  

29for n in 0..group.len() { //group.len() = 4 -> 0..4 ? check group.len()on each iteration  

30 println!("Current Person : {}", group[n]);  

31}  

32​  

33for person in group.iter() { //? group.iter() turn the array into a simple iterator  

34 println!("Current Person : {}", person);  

35}

36

以上，希望对你有用。

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1如果遇到什么问题，欢迎加入：rust新手群，在这里我可以提供一些简单的帮助，加微信：360369487，注明：博客园+rust

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本人精通java高并发，DDD，微服务等技术实践，以及python，golang技术栈。 本人姓名郭莹城，坐标深圳，前IBM架构师、咨询师、敏捷开发技术教练，前IBM区块链研究小组成员、十四年架构设计工作经验，《区块链核心技术与应用》作者之一， 现有成熟团队提供区块链开发相关业务（公链，交易所，钱包，Dapp,智能合约）。 工作微信&QQ：360369487，交易所开发与区块链钱包开发业务，加我注明：博客园+开发，想学习golang和rust的同学，也可以加我微信，备注：博客园+golang或博客园+rust,谢谢！

参考文章：
https://learning-rust.github.io/docs/a10.control_flows.html