Adapter

インターフェイスの変換を行い、互換性のないクラスを利用できるようにする
継承アダプタは、クライアントが使用するインターフェイスを実装し、既存のクラスを継承する
委譲アダプタは、クライアントが使用する抽象クラスを実装し、既存クラスの処理を委譲する

#include <iostream>
using namespace std;
 
class Target {
public:
    virtual void targetMethod() {
        cout << "Original Method." << endl;
    }
};
 
class Adaptee {
public:
    void Method() {
        cout << "Adaptee Method." << endl;
    }
};
 
// 継承 Adapter
class DeriveAdapter : public Target, public Adaptee {
public:
    virtual void targetMethod() {
        Method();   // Adaptee::method()
    }
};
 
// 包含 Adapter
class InclusionAdapter : public Target {
public:
    virtual void targetMethod() {
        _adaptee.Method();
    }
private:
    Adaptee _adaptee;
};
 
// client
int main() {
    Target *t = new Target();
    t->targetMethod();
    // 継承 Adapter
    Target *t1 = new DeriveAdapter();
    t1->targetMethod();
    // 包含 Adapter
    Target *t2 = new InclusionAdapter();
    t2->targetMethod();
 
    delete t;
    delete t1;
    delete t2;
    return 0;
}

出力

Original Method.
Adaptee Method.
Adaptee Method.

http://www.dofactory.com/Patterns/PatternAdapter.aspx#_self1
をC++にした（structural example）

#include <iostream>
using namespace std;
 
// The 'Target' class
class Target {
public:
    virtual ~Target() { }
    virtual void Request() {
        cout << "Called Target Request()" << endl;
    }
};
 
// The 'Adaptee' class
class Adaptee {
public:
    void SpecificRequest() {
        cout << "Called SpecificRequest()" << endl;
    }
};
 
// The 'Adapter' class
class Adapter : public Target {
public:
    Adapter() {
        _adaptee = new Adaptee();
    }
    virtual ~Adapter() {
        delete _adaptee;
    }
    virtual void Request() {
        _adaptee->SpecificRequest();
    }
private:
    Adaptee *_adaptee;
};
 
// client
int main() {
    Target *target = new Adapter();
    target->Request();
    delete target;
    return 0;
}

出力

Called SpecificRequest()

http://www.dofactory.com/Patterns/PatternAdapter.aspx#_self2
をC++にした（real world example）

#include <iostream>
#include <string>
#include <ctype.h>
using namespace std;
 
// The 'Target' class
class Compound {
public:
    // constructor
    Compound(const string &chemical) {
        _chemical = chemical;
    }
    virtual void Display() {
        cout << endl << "Compound: " << _chemical << " ------ " << endl;
    }
protected:
    string _chemical;
    float _boilingPoint;
    float _meltingPoint;
    double _molecularWeight;
    string _molecularFormula;
};
 
// The 'Adaptee' class
class ChemicalDatabank {
public:
    // 'legacy API'
    float GetCriticalPoint(string compound, const string point) {
        ToLower(compound);
        // Melting Point
        if (point == "M") {
            if (compound == "water") {
                return 0.0f;
            }
            else if (compound == "benzene") {
                return 5.5f;
            }
            else if (compound == "ethanol") {
                return -114.1f;
            }
            else {
                return 0.0f;
            }
        }
        // Biling Point
        else {
            if (compound == "water") {
                return 100.0f;
            }
            else if (compound == "benzene") {
                return 80.1f;
            }
            else if (compound == "ethanol") {
                return 78.3f;
            }
            else {
                return 0.0f;
            }
        }
    }
    string GetMolecularStructure(string compound) {
        string ret;
        ToLower(compound);
        if (compound == "water") {
            ret = "H2O";
        }
        else if (compound == "benzene") {
            ret = "C6H6";
        }
        else if (compound == "ethanol") {
            ret = "C2H5OH";
        }
        return ret;
    }
    double GetMolecularWeight(string compound) {
        ToLower(compound);
        if (compound == "water") {
            return 18.015;
        }
        else if (compound == "benzene") {
            return 78.1134;
        }
        else if (compound == "ethanol") {
            return 46.0688;
        }
        else {
            return 0.0;
        }
    }
private:
    void ToLower(string &str) {
        string::iterator it;
        for (it=str.begin(); it!=str.end(); ++it) {
            *it = tolower(*it);
        }
    }
};
 
// The 'Adapter' class
class RichCompound : public Compound {
public:
    // constructor
    RichCompound(const string &name) : Compound(name) {
        _bank = NULL;
    }
    virtual ~RichCompound() {
        if (_bank != NULL) delete _bank;
    }
    virtual void Display() {
        if (_bank == NULL) _bank = new ChemicalDatabank();
 
        _boilingPoint = _bank->GetCriticalPoint(_chemical, "B");
        _meltingPoint = _bank->GetCriticalPoint(_chemical, "M");
        _molecularWeight = _bank->GetMolecularWeight(_chemical);
        _molecularFormula = _bank->GetMolecularStructure(_chemical);
 
        Compound::Display();
        cout << " Formula: " << _molecularFormula << endl;
        cout << " Weight : " << _molecularWeight << endl;
        cout << " Melting Pt: " << _meltingPoint << endl;
        cout << " Boiling Pt: " << _boilingPoint << endl;
    }
private:
    ChemicalDatabank *_bank;
};
 
// client
int main() {
    // Non-adapted chemical compound
    Compound *unknown = new Compound("Unknown");
    unknown->Display();
    // Adapted chemical compounds
    Compound *water = new RichCompound("Water");
    water->Display();
    Compound *benzene = new RichCompound("Benzene");
    benzene->Display();
    Compound *ethanol = new RichCompound("Ethanol");
    ethanol->Display();
 
    delete unknown;
    delete water;
    delete benzene;
    delete ethanol;
    return 0;
}

出力

Compound: Unknown ------

Compound: Water ------
Formula: H2O
Weight : 18.015
Melting Pt: 0
Boiling Pt: 100

Compound: Benzene ------
Formula: C6H6
Weight : 78.1134
Melting Pt: 5.5
Boiling Pt: 80.1

Compound: Ethanol ------
Formula: C2H5OH
Weight : 46.0688
Melting Pt: -114.1
Boiling Pt: 78.3