The original example is taken form the Design Patterns book
01
Specify the new desired interface
Design a “wrapper” class that can “impedance match” the old to the new
The client uses (is coupled to) the new interface
The adapter/wrapper “maps” to the legacy implementation
02
#include "stdafx.h" #includeusing namespace std; class ExecuteInterface { public: // 1. Specify the new interface virtual ~ExecuteInterface(){} virtual void execute() = 0; };
2. Design a "wrapper" or "adapter" class
templateclass ExecuteAdapter: public ExecuteInterface { public: ExecuteAdapter(TYPE *o, void(TYPE:: *m)()) { object = o; method = m; } ~ExecuteAdapter() { delete object; } // 4. The adapter/wrapper "maps" the new to the legacy implementation void execute() { /* the new */ (object->*method)(); } private: TYPE *object; // ptr-to-object attribute void(TYPE:: *method)(); /* the old */ // ptr-to-member-function attribute };
// The old: three totally incompatible classes
// no common base class,
class Fea {
public:
// no hope of polymorphism
~Fea() {
cout << "Fea::dtor" << endl; }
void doThis() { cout << "Fea::doThis()" << endl; } };
class Feye { public:~Feye() {
cout << "Feye::dtor" << endl; }
void doThat() {
cout << "Feye::doThat()" << endl; } };
class Pheau {
public:
~Pheau() {
cout << "Pheau::dtor" << endl; }
void doTheOther() {
cout << "Pheau::doTheOther()" << endl; } }; /* the new is returned */ ExecuteInterface **initialize() {
ExecuteInterface **array = new ExecuteInterface *[3]; /* the old is below */
array[0] = new ExecuteAdapter < Fea > (new Fea(), &Fea::doThis);
array[1] = new ExecuteAdapter < Feye > (new Feye(), &Feye::doThat);
array[2] = new ExecuteAdapter < Pheau > (new Pheau(), &Pheau::doTheOther);
return array;
}
int main() {
ExecuteInterface **objects = initialize();
for (int i = 0; i < 3; i++) { objects[i]->execute();
}
// 3. Client uses the new (polymporphism)
for (i = 0; i < 3; i++) {
delete objects[i];
}
delete objects;
return 0;
}
The result output:
Fea::doThis() Feye::doThat() Pheau::doTheOther() Fea::dtor Feye::dtor Pheau::dtor
