[英]C++ catch(std::exception & e ) vs. catch(...)
I know the difference in handling of both of these catches, but what does it take for the ellipse to catch something the std::exception catch wouldn't catch?我知道处理这两个捕获的区别,但是椭圆捕获 std::exception 捕获不会捕获的东西需要什么?
For example:例如:
try
{
throw std::runtime("runtime error!");
}
catch(const std::exception& e)
{
std::cout << "Exception: " << e;
}
catch(...)
{
std::cout << "How did I get here?";
throw;
}
I've seen examples of code that use both of these in conjunction, but I've not seen a reason you would do both.我已经看到将这两种方法结合使用的代码示例,但我没有看到您同时使用这两种方法的理由。
catch(const std::exception& e)
Will catch std exceptions only.只会捕获 std 异常。
catch(...)
Will catch everything there after.之后会抓住一切。
You can handle integers and other types ( http://www.cplusplus.com/doc/tutorial/exceptions/ )您可以处理整数和其他类型( http://www.cplusplus.com/doc/tutorial/exceptions/ )
For example:例如:
catch(int e)
While it's definitely a good idea to do so, you don't have to derive your custom exceptions from std::exception
.虽然它绝对是一个好主意,这样做,你就不必从派生自定义异常
std::exception
。 C++ allows you to throw practically any object type. C++ 允许您抛出几乎任何对象类型。
So throw 1;
所以
throw 1;
will not be handled by your first handler, for example.例如,不会由您的第一个处理程序处理。 And neither will...
而且也不会...
class MyCustomException { // Doesn't derive
///
};
... if it was thrown. ...如果它被抛出。
You probably meant:你可能的意思是:
throw std::runtime_error("runtime error!"); // not std::runtime
The std::runtime_error is derived from the std::exception so your first catch block is fired up as it catches exceptions of type std::exception
. std::runtime_error派生自std::exception ,因此您的第一个 catch 块在捕获
std::exception
类型的异常时被触发。 And there you probably meant:你可能的意思是:
std::cout << "Exception: " << e.what(); // not e
If you threw anything else other than the std::run_time
or std::exception
and its derivatives, the second catch
block would be triggered.如果您抛出
std::run_time
或std::exception
及其派生类以外的任何其他内容,则将触发第二个catch
块。 Useful reading from the C++ FAQ: What should I throw?来自 C++ FAQ 的有用阅读:我应该抛出什么?
As written, the throw
statement throws an object whose type is derived from std::exception
, so it's caught by the first catch
clause.正如所写,
throw
语句抛出一个类型派生自std::exception
的对象,因此它被第一个catch
子句catch
。 If you change the throw to throw 3;
如果你把投掷改为
throw 3;
the exception will be caught by the second catch
clause, not the first.异常将被第二个
catch
子句catch
,而不是第一个。
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