[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:
/ Simplest Example
let team_size = 7;
if team_size < 5 {
println!("Small");
} else if team_size < 10 {
println!("Medium");
} else {
println!("Large");
}
// partially refactored code
let team_size = 7;
let team_size_in_text;
if team_size < 5 {
team_size_in_text = "Small";
} else if team_size < 10 {
team_size_in_text = "Medium";
} else {
team_size_in_text = "Large";
}
println!("Current team size : {}", team_size_in_text);
//optimistic code
let team_size = 7;
let team_size_in_text = if team_size < 5 {
"Small" //⭐️no ;
} else if team_size < 10 {
"Medium"
} else {
"Large"
};
println!("Current team size : {}", team_size_in_text);
let is_below_eighteen = if team_size < 18 { true } else { false };
模式匹配 match :
let tshirt_width = 20;
let tshirt_size = match tshirt_width {
16 => "S", // check 16
17 | 18 => "M", // check 17 and 18
19 ... 21 => "L", // check from 19 to 21 (19,20,21)
22 => "XL",
_ => "Not Available",
};
println!("{}", tshirt_size); // L
let is_allowed = false;
let list_type = match is_allowed {
true => "Full",
false => "Restricted"
// no default/ _ condition can be skipped
// Because data type of is_allowed is boolean and all possibilities checked on conditions
};
println!("{}", list_type); // Restricted
let marks_paper_a: u8 = 25;
let marks_paper_b: u8 = 30;
let output = match (marks_paper_a, marks_paper_b) {
(50, 50) => "Full marks for both papers",
(50, _) => "Full marks for paper A",
(_, 50) => "Full marks for paper B",
(x, y) if x > 25 && y > 25 => "Good",
(_, _) => "Work hard"
};
println!("{}", output); // Work hard
while:
let mut a = 1;
while a <= 10 {
println!("Current value : {}", a);
a += 1; //no ++ or -- on Rust
}
// Usage of break and continue
let mut b = 0;
while b < 5 {
if b == 0 {
println!("Skip value : {}", b);
b += 1;
continue;
} else if b == 2 {
println!("Break At : {}", b);
break;
}
println!("Current value : {}", b);
b += 1;
}
// Outer break
let mut c1 = 1;
'outer_while: while c1 < 6 { //set label outer_while
let mut c2 = 1;
'inner_while: while c2 < 6 {
println!("Current Value : [{}][{}]", c1, c2);
if c1 == 2 && c2 == 2 { break 'outer_while; } //kill outer_while
c2 += 1;
}
c1 += 1;
}
loop
loop {
println!("Loop forever!");
}
// Usage of break and continue
let mut a = 0;
loop {
if a == 0 {
println!("Skip Value : {}", a);
a += 1;
continue;
} else if a == 2 {
println!("Break At : {}", a);
break;
}
println!("Current Value : {}", a);
a += 1;
}
// Outer break
let mut b1 = 1;
'outer_loop: loop { //set label outer_loop
let mut b2 = 1;
'inner_loop: loop {
println!("Current Value : [{}][{}]", b1, b2);
if b1 == 2 && b2 == 2 {
break 'outer_loop; // kill outer_loop
} else if b2 == 5 {
break;
}
b2 += 1;
}
b1 += 1;
}
for
for a in 0..10 { //(a = o; a <10; a++) // 0 to 10(exclusive)
println!("Current value : {}", a);
}
// Usage of break and continue
for b in 0..6 {
if b == 0 {
println!("Skip Value : {}", b);
continue;
} else if b == 2 {
println!("Break At : {}", b);
break;
}
println!("Current value : {}", b);
}
// Outer break
'outer_for: for c1 in 1..6 { //set label outer_for
'inner_for: for c2 in 1..6 {
println!("Current Value : [{}][{}]", c1, c2);
if c1 == 2 && c2 == 2 { break 'outer_for; } //kill outer_for
}
}
// Working with arrays/vectors
let group : [&str; 4] = ["Mark", "Larry", "Bill", "Steve"];
for n in 0..group.len() { //group.len() = 4 -> 0..4 ???? check group.len()on each iteration
println!("Current Person : {}", group[n]);
}
for person in group.iter() { //???? group.iter() turn the array into a simple iterator
println!("Current Person : {}", person);
}
以上,希望对你有用。
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参考文章: https://learning-rust.github.io/docs/a10.control_flows.html
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