readme.md

C++ Example

#include <iostream>
#include <string>

/**
 * Bridge Design Pattern
 *
 * Intent: Lets you split a large class or a set of closely related classes into
 * two separate hierarchies—abstraction and implementation—which can be
 * developed independently of each other.
 *
 *               A
 *            /     \                        A         N
 *          Aa      Ab        ===>        /     \     / \
 *         / \     /  \                 Aa(N) Ab(N)  1   2
 *       Aa1 Aa2  Ab1 Ab2
 */

/**
 * The Implementation defines the interface for all implementation classes. It
 * doesn't have to match the Abstraction's interface. In fact, the two
 * interfaces can be entirely different. Typically the Implementation interface
 * provides only primitive operations, while the Abstraction defines higher-
 * level operations based on those primitives.
 */

class Implementation {
 public:
  virtual ~Implementation() {}
  virtual std::string OperationImplementation() const = 0;
};

/**
 * Each Concrete Implementation corresponds to a specific platform and
 * implements the Implementation interface using that platform's API.
 */
class ConcreteImplementationA : public Implementation {
 public:
  std::string OperationImplementation() const override {
    return "ConcreteImplementationA: Here's the result on the platform A.\n";
  }
};
class ConcreteImplementationB : public Implementation {
 public:
  std::string OperationImplementation() const override {
    return "ConcreteImplementationB: Here's the result on the platform B.\n";
  }
};

/**
 * The Abstraction defines the interface for the "control" part of the two class
 * hierarchies. It maintains a reference to an object of the Implementation
 * hierarchy and delegates all of the real work to this object.
 */

class Abstraction {
  /**
   * @var Implementation
   */
 protected:
  Implementation* implementation_;

 public:
  Abstraction(Implementation* implementation) : implementation_(implementation) {
  }

  virtual ~Abstraction() {
  }

  virtual std::string Operation() const {
    return "Abstraction: Base operation with:\n" +
           this->implementation_->OperationImplementation();
  }
};
/**
 * You can extend the Abstraction without changing the Implementation classes.
 */
class ExtendedAbstraction : public Abstraction {
 public:
  ExtendedAbstraction(Implementation* implementation) : Abstraction(implementation) {
  }
  std::string Operation() const override {
    return "ExtendedAbstraction: Extended operation with:\n" +
           this->implementation_->OperationImplementation();
  }
};

/**
 * Except for the initialization phase, where an Abstraction object gets linked
 * with a specific Implementation object, the client code should only depend on
 * the Abstraction class. This way the client code can support any abstraction-
 * implementation combination.
 */
void ClientCode(const Abstraction& abstraction) {
  // ...
  std::cout << abstraction.Operation();
  // ...
}
/**
 * The client code should be able to work with any pre-configured abstraction-
 * implementation combination.
 */

int main() {
  Implementation* implementation = new ConcreteImplementationA;
  Abstraction* abstraction = new Abstraction(implementation);
  ClientCode(*abstraction);
  std::cout << std::endl;
  delete implementation;
  delete abstraction;

  implementation = new ConcreteImplementationB;
  abstraction = new ExtendedAbstraction(implementation);
  ClientCode(*abstraction);

  delete implementation;
  delete abstraction;

  return 0;
}

Abstraction: Base operation with:
ConcreteImplementationA: Here's the result on the platform A.

ExtendedAbstraction: Extended operation with:
ConcreteImplementationB: Here's the result on the platform B.