Function-try Blocks

A function-try block catches exceptions generated from a call made in a constructor's initialization list.

Example

The following example uses a function-try block:

// NVC_Function_Try.cpp
// Compile by using /EHsc
#include <iostream>
#include <ostream>
#include <stdexcept>
#include <string>
using namespace std;

class Name 
{
public:
    Name(const string& strFirstName, const string& strLastName)
    {
        if(strFirstName == "")
        {
            throw runtime_error("Error in Name::Name(): first name parameter must not be blank.");
        }
        
        if(strLastName == "")
        {
            throw runtime_error("Error in Name::Name(): last name parameter must not be blank.");
        }

        m_firstName = strFirstName;
        m_lastName = strLastName;

        cout << "Inside Name::Name(): My name is " << GetName() << "." << endl;
    }

    ~Name() 
    {
        cout << "Inside Name::~Name(): Destroying " << GetName() << "." << endl;
    }

    string GetName()
    {
        return m_firstName + " " + m_lastName;
    }

private:
    string m_firstName;
    string m_lastName;
};

class Person
{
public:
    Person(const string& strFirstName, const string& strLastName)
    // begin function-try block
    try : m_name(strFirstName, strLastName){}
    catch (const runtime_error& err)
    {
        cout << "Caught exception inside Person::Person()." << endl;
        cout << err.what() << endl;
        // The exception will be automatically rethrown.
    }

    ~Person()
    {
        cout << "Inside Person::~Person(): Destroying " << m_name.GetName() << "." << endl;
    }

private:
    Name m_name;
};

int main()
{
    try
    {
        // Test 1 - Valid Parameters 
        {
            cout << "Attempting to construct an object of class Person." << endl;
            cout << "Passing parameters: \"John\", \"Smith\"" << endl;
            Person person1("John", "Smith");
        }

        cout << "Test 1 completed." << endl;

        // Test 2 - Invalid first name parameter
        {
            // Note that an exception will be thrown in Name's constructor,
            //  as the first name parameter must not be blank.
            //  Because this exception is thrown, person2's destructor
            //  is never called.
            cout << "Attempting to construct an object of class Person." << endl;
            cout << "Passing parameters: \"\", \"Jones\"" << endl;
            Person person2("", "Jones");
        }
    }
    catch (const runtime_error&)
    {
        cout << "Exception caught within main()." << endl;
    }
}

// Output:
// --------------------------
// Attempting to construct an object of class Person.
// Passing parameters: "John", "Smith"
// Inside Name::Name(): My name is John Smith.
// Inside Person::~Person(): Destroying John Smith.
// Inside Name::~Name(): Destroying John Smith.
// Test 1 completed.
// Attempting to construct an object of class Person.
// Passing parameters: "", "Jones"
// Caught exception inside Person::Person().
// Error in Name::Name(): first name parameter must not be blank.
// Exception caught within main().

See Also

Reference

C++ Exception Handling

try, catch, and throw Statements (C++)