C ++，在多个块中捕获用户定义的异常 [英] C++, catch user-defined exceptions in multiple blocks

问题描述

假设以下示例.从std :: exception派生的类A-C:

Suppose the following example. There are classes A-C derived from std::exception:

#include <exception>
#include <string>
#include <iostream>

class A : public std::exception {
std::string a_text;

public:
 A(const std::string & a_text_) : a_text(a_text_) {}
 virtual ~A() throw() { }
};

class B : public A {
 const std::string b_text;

public:
 B(const std::string &a_text_, const std::string & b_text_) : A(a_text_), b_text(b_text_) {}
 virtual ~B() throw() {}
};

template <typename T>
class C : public B {
 T x;

public:
 C(const std::string & a_text_, const std::string & b_text_, const T x_) :
    B (b_text_, a_text_), x(x_) { }

 virtual ~C() throw() {};
};

到目前为止，我已经确信泛化模式会在多个块中捕获派生类的异常.

So far I have been convinced that generalizing pattern catches the exception of the derived class in multiple blocks.

int main() {
 try {
    throw C<double>("a", "b", 10);
 }

 catch (C<double> &c1) {
    std::cout << " C";
 }

 catch (B &b1) {
    std::cout << " B";
 }
}

不幸的是，第二个引用B的块被跳过了.问题出在哪儿?感谢您的帮助.

Unfortunately, the second block referring to B is skipped. Where is the problem? Thanks for your help.

推荐答案

只有匹配的第一个catch块将要执行.您可以使用"throw;"将现有异常重新抛出.语句，但我不确定是否会在下一个catch块或仅在外部try-catch中继续搜索.

Only the first catch block that matches is going to execute. You can re-throw the existing exception with the "throw;" statement but I am not sure if that will continue the search at the next catch block or only in a outer try-catch.

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