November 2005
Beginner to intermediate
594 pages
16h 23m
English
You have to initialize your data members in the constructor’s initializer list, and, therefore, cannot use the approach described in Recipe 9.2.
Use a special syntax for try and catch that catches exceptions thrown in the initializer list. Example 9-3 shows how.
Example 9-3. Handling exceptions in an initializer
#include <iostream>
#include <stdexcept>
using namespace std;
// Some device
class Device {
public:
Device(int devno) {
if (devno == 2)
throw runtime_error("Big problem");
}
~Device() {}
private:
Device();
};
class Broker {
public:
Broker (int devno1, int devno2)
try : dev1_(Device(devno1)), // Create these in the initializer
dev2_(Device(devno2)) {} // list.
catch (...) {
throw; // Log the message or translate the error here (see
// the discussion)
}
~Broker() {}
private:
Broker();
Device dev1_;
Device dev2_;
};
int main() {
try {
Broker b(1, 2);
}
catch(exception& e) {
cerr << "Exception: " << e.what() << endl;
}
}The syntax for handling exceptions in initializers looks a little different from the
traditional C++ syntax because it uses the try block as
the constructor body. The critical part of Example 9-3 is the Broker constructor:
Broker (int devno1, int devno2) // Constructor header is the same try : // Same idea as a try {...} block dev1_(Device(devno1)), // The initializers follow dev2_(Device(devno2)) { // This is the constructor body. } catch (...) { // The catch handler is *after* throw; // the ...