C++ Adapter Design Pattern

Adapter pattern is a structural design pattern. Also referred as wrapper pattern. An adapter design pattern allows classes to work together that normally could not because of incompatible interfaces, by providing its interface to clients while using the original interface. This article provides an introduction to adapter design pattern with a sample implementation in C++.

Adapter design pattern

• Adapter pattern is a structural design pattern.
• Also referred as wrapper pattern.
• An adapter allows classes to work together that normally could not because of incompatible interfaces, by providing its interface to clients while using the original interface.
• The adapter translates calls to its interface into calls to the original interface.
• The adapter is also responsible for transforming data into appropriate forms.
• The adapter is created by implementing or inheriting both the interface that is expected and the interface that is pre-existing.
• It is typical for the expected interface to be created as a abstract class.

Adapter design pattern implementation

#include <iostream>
#include <list>
#include <cstdlib>
using namespace std;

// Legacy account
class LegacyAccount
{
    int no;

public:
    LegacyAccount(int no)
    {
        this->no = no;
    }

    void legacyAccountPrint()
    {
        cout << "Display legacy account details " << no << endl;
    }
};

// Renewed interface
class RenewedAccountIntf
{
public:
    virtual void display() = 0;
};

// Renewed account object
class Account : public RenewedAccountIntf
{
    string no;

public:
    Account(string no) {
        this->no = no;
    }

    void display()
    {
        cout << "Display renewed account details " << no << endl;
    }
};

// Legacy account adapter to renewed interface
class LegacyAccountAdapter : public LegacyAccount,
        public RenewedAccountIntf
{
public:
    LegacyAccountAdapter(string no) :
        LegacyAccount(atoi(no.c_str()))
    {
    }

    void display()
    {
        this->legacyAccountPrint();
    }
};


// Test program
int main()
{
    list<RenewedAccountIntf*> accountList;
    accountList.push_back(new Account("accountholder 1"));
    accountList.push_back(new Account("accountholder 2"));
    accountList.push_back(new LegacyAccountAdapter("12345"));

    while ( ! accountList.empty() )
    {
        RenewedAccountIntf* obj = accountList.front();
        obj->display();
        accountList.pop_front();
    }
}

OUTPUT:-

Display renewed account details accountholder 1
Display renewed account details accountholder 2
Display legacy account details 12345