英文:
How to end a loop with a function?
问题
void Stop() {
break;
}
int main() {
while (true) {
std::cout << "NO!" << '\n';
Stop();
}
std::cout << "YES!";
}
在我的项目中，我需要使用一个函数来结束 while 循环，我该如何修改这个无法编译的示例？
我有一个使用 throw 的想法，但是否有其他更好的解决方案？
<details>
<summary>英文:</summary>
void Stop() {
break;
}
int main() {
while (true) {
std::cout << "NO!" << '\n';
Stop();
}
std::cout << "YES!";
}
In my project I need to end `while` using a function, how can I change this uncompilable example?
I have an idea to use `throw`, but what about other better solutions?
</details>
# 答案1
**得分**: 4
你真的不能这样做。在**任何**编程语言中，使用异常来管理控制流和业务逻辑被认为是一种不良实践。你可以做的是，在循环中返回一个布尔标志以退出循环，例如，当此条件太复杂以直接编码在循环中时：
```cpp
bool Stop(int idx) {
return idx > 10;
}
int main() {
int counter = 0;
while (true) {
std::cout << "NO!" << '\n';
const bool is_invalid = Stop(counter);
if (is_invalid) break;
++counter;
}
std::cout << "YES!";
}
英文:
You can't really do this. Using exceptions for managing control flow and business logic is considered to be a bad practice in any programming language. What you can do, you could return a boolean flag for breaking out of the loop, for example, when this condition is too complex to be coded directly in the loop:
bool Stop(int idx) {
return idx > 10;
}
int main() {
int counter = 0;
while (true) {
std::cout << "NO!" << '\n';
const bool is_invalid = Stop(counter);
if (is_invalid) break;
++counter;
}
std::cout << "YES!";
}
答案2
得分: 3
这应该可以工作，但设计不够好。拿它作为一种示例，演示需要改变的部分以使其工作。
bool isRunning = false;
void Stop() {
isRunning = false;
}
int main() {
isRunning = true;
while (isRunning) {
std::cout << "NO!" << '\n';
Stop();
}
std::cout << "YES!";
}
英文:
This should work, but it's not good design. Take it with a grain of salt, it's just to demonstrate what you need to change to make it work.
bool isRunning = false;
void Stop() {
isRunnning = false;
}
int main() {
isRunning = true;
while (isRunning) {
std::cout << "NO!" << '\n';
Stop();
}
std::cout << "YES!";
}
答案3
得分: 3
使该函数返回停止条件的值。我假设这只是一个简化的示例。在真实的示例中，该函数将接受参数，并且要么返回 true 要么返回 false（如果它总是无条件地停止循环，那么首先根本不需要循环，因此也不需要函数来停止循环）：
bool Stop() {
return false;
}
int main() {
do {
std::cout << "NO!" << '\n';
} while (Stop());
std::cout << "YES!";
}
英文:
Make the function return the value of the stop condition. I suppose this is a simplified example. In a real example the function would take parameters and either return true or false (if it always stops the loop unconditionally, then there is no need for a loop in the first place, hence also no need for the function to stop the loop):
bool Stop() {
return false;
}
int main() {
do {
std::cout << "NO!" << '\n';
} while ( Stop() );
std::cout << "YES!";
}
答案4
得分: 2
你可以通过对事物有控制来做类似的事情。
class Server {
public:
Server() = default;
void start() {
loop();
}
void stop() {
isRunning = false;
}
private:
void loop() {
while (isRunning) {
// 随时停止
}
}
private:
bool isRunning = true;
};
int main() {
Server sv;
}
英文:
You can do something similar by having control over things.
class Server {
public:
Server() = default;
void start() {
loop();
}
void stop() {
isRunning = false;
}
private:
void loop() {
while (isRunning) {
// stop whenever you want
}
}
private:
bool isRunning = true;
};
int main() {
Server sv;
}
答案5
得分: 0
你还可以使用一个布尔变量来实现无限循环，并通过某个函数的引用来更改它：
#include <iostream>
void Stop(bool& running) {
running = false;
}
int main() {
bool running = true;
while (running) {
// ...
std::cout << "inside loop" << std::endl;
Stop(running);
}
std::cout << "outside loop" << std::endl;
return 0;
}
英文:
You can also use a bool variable for the infinite loop and change it by reference from some function:
#include <iostream>
void Stop(bool& running) {
running = false;
}
int main() {
bool running = true;
while (running) {
// ...
std::cout << "inside loop" << std::endl;
Stop(running);
}
std::cout << "outside loop" << std::endl;
return 0;
}
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