当代码流是这样的:
if(check())
{
...
...
if(check())
{
...
...
if(check())
{
...
...
}
}
}
我通常看到这种方法可以避免上述混乱的代码流:
do {
if(!check()) break;
...
...
if(!check()) break;
...
...
if(!check()) break;
...
...
} while(0);
有什么更好的方法可以避免这种工作/黑客，从而使其成为更高级别(行业级别)的代码?
任何跳出盒子的建议都是欢迎的!
当前回答
typedef bool (*Checker)();
Checker * checkers[]={
&checker0,&checker1,.....，&checkerN,NULL
};
bool checker1(){
if(condition){
.....
.....
return true;
}
return false;
}
bool checker2(){
if(condition){
.....
.....
return true;
}
return false;
}
......
void doCheck(){
Checker ** checker = checkers;
while( *checker && (*checker)())
checker++;
}
怎么样?
其他回答
我就是这么做的。
void func() {
if (!check()) return;
...
...
if (!check()) return;
...
...
if (!check()) return;
...
...
}
I'm adding an answer for the sake of completeness. A number of other answers pointed out that the large condition block could be split out into a separate function. But as was also pointed out a number of times is that this approach separates the conditional code from the original context. This is one reason that lambdas were added to the language in C++11. Using lambdas was suggested by others but no explicit sample was provided. I've put one in this answer. What strikes me is that it feels very similar to the do { } while(0) approach in many ways - and maybe that means it's still a goto in disguise....
earlier operations
...
[&]()->void {
if (!check()) return;
...
...
if (!check()) return;
...
...
if (!check()) return;
...
...
}();
later operations
使用异常。您的代码将看起来更加清晰(并且创建异常正是为了处理程序执行流中的错误)。有关清理资源(文件描述符，数据库连接等)，请阅读文章“为什么c++不提供一个“finally”结构?”
#include <iostream>
#include <stdexcept> // For exception, runtime_error, out_of_range
int main () {
try {
if (!condition)
throw std::runtime_error("nope.");
...
if (!other condition)
throw std::runtime_error("nope again.");
...
if (!another condition)
throw std::runtime_error("told you.");
...
if (!yet another condition)
throw std::runtime_error("OK, just forget it...");
}
catch (std::runtime_error &e) {
std::cout << e.what() << std::endl;
}
catch (...) {
std::cout << "Caught an unknown exception\n";
}
return 0;
}
也许就像这样
#define EVER ;;
for(EVER)
{
if(!check()) break;
}
或者使用异常
try
{
for(;;)
if(!check()) throw 1;
}
catch()
{
}
使用异常还可以传递数据。
为什么标记法没有被回答，这是自古以来使用的方法。
//you can use something like this (pseudocode)
long var = 0;
if(condition) flag a bit in var
if(condition) flag another bit in var
if(condition) flag another bit in var
............
if(var == certain number) {
Do the required task
}
