Editing Bridge pattern (section)

== Example ==
<!-- Wikipedia is not a list of examples. Do not add examples from your favorite programming language here; this page exists to explain the design pattern, not to show how it interacts with subtleties of every language under the sun. Feel free to add examples here: http://en.wikibooks.org/wiki/Computer_Science/Design_Patterns/Bridge_pattern -->
=== C# ===
Bridge pattern compose objects in tree structure. It decouples abstraction from implementation. Here abstraction represents the client from which the objects will be called. An example implemented in C# is given below
<syntaxhighlight lang="csharp">
// Helps in providing truly decoupled architecture
public interface IBridge
{
    void Function1();
    void Function2();
}

public class Bridge1 : IBridge
{
    public void Function1()
    {
        Console.WriteLine("Bridge1.Function1");
    }

    public void Function2()
    {
        Console.WriteLine("Bridge1.Function2");
    }
}

public class Bridge2 : IBridge
{
    public void Function1()
    {
        Console.WriteLine("Bridge2.Function1");
    }

    public void Function2()
    {
        Console.WriteLine("Bridge2.Function2");
    }
}

public interface IAbstractBridge
{
    void CallMethod1();
    void CallMethod2();
}

public class AbstractBridge : IAbstractBridge
{
    public IBridge bridge;

    public AbstractBridge(IBridge bridge)
    {
        this.bridge = bridge;
    }

    public void CallMethod1()
    {
        this.bridge.Function1();
    }

    public void CallMethod2()
    {
        this.bridge.Function2();
    }
}
</syntaxhighlight>
The Bridge classes are the Implementation that uses the same interface-oriented architecture to create objects. On the other hand, the abstraction takes an instance of the implementation class and runs its method. Thus, they are completely decoupled from one another.

=== Crystal ===
<syntaxhighlight lang="crystal">
abstract class DrawingAPI
  abstract def draw_circle(x : Float64, y : Float64, radius : Float64)
end

class DrawingAPI1 < DrawingAPI
  def draw_circle(x : Float, y : Float, radius : Float)
    "API1.circle at #{x}:#{y} - radius: #{radius}"
  end
end

class DrawingAPI2 < DrawingAPI
  def draw_circle(x : Float64, y : Float64, radius : Float64)
    "API2.circle at #{x}:#{y} - radius: #{radius}"
  end
end

abstract class Shape
  protected getter drawing_api : DrawingAPI

  def initialize(@drawing_api)
  end

  abstract def draw
  abstract def resize_by_percentage(percent : Float64)
end

class CircleShape < Shape
  getter x : Float64
  getter y : Float64
  getter radius : Float64

  def initialize(@x, @y, @radius, drawing_api : DrawingAPI)
    super(drawing_api)
  end

  def draw
    @drawing_api.draw_circle(@x, @y, @radius)
  end

  def resize_by_percentage(percent : Float64)
    @radius *= (1 + percent/100)
  end
end

class BridgePattern
  def self.test
    shapes = [] of Shape
    shapes << CircleShape.new(1.0, 2.0, 3.0, DrawingAPI1.new)
    shapes << CircleShape.new(5.0, 7.0, 11.0, DrawingAPI2.new)

    shapes.each do |shape|
      shape.resize_by_percentage(2.5)
      puts shape.draw
    end
  end
end

BridgePattern.test
</syntaxhighlight>

Output
<pre>
API1.circle at 1.0:2.0 - radius: 3.075
API2.circle at 5.0:7.0 - radius: 11.275
</pre>

=== C++ ===
<syntaxhighlight lang="cpp">
import std;

class DrawingAPI {
  public:
    virtual ~DrawingAPI() = default;
    virtual std::string DrawCircle(float x, float y, float radius) const = 0;
};

class DrawingAPI01 : public DrawingAPI {
  public:
    std::string DrawCircle(float x, float y, float radius) const override {
      return std::format("API01.circle at {}:{} - radius: {}", std::to_string(x), std::to_string(y), std::to_string(radius)); 
    }
};

class DrawingAPI02 : public DrawingAPI {
  public:
    std::string DrawCircle(float x, float y, float radius) const override {
      return std::format("API02.circle at {}:{} - radius: {}", std::to_string(x), std::to_string(y), std::to_string(radius));
    }
};

class Shape {
  public:
    Shape(const DrawingAPI& drawing_api):
    drawing_api_(drawing_api) {}
    virtual ~Shape() = default;

    virtual std::string Draw() const = 0;
    virtual float ResizeByPercentage(const float percent) = 0;

  protected:
    const DrawingAPI& drawing_api_;
};

class CircleShape: public Shape {
  public:    
    CircleShape(float x, float y, float radius, const DrawingAPI& drawing_api): 
    Shape(drawing_api), x_(x), y_(y), radius_(radius) {}

    std::string Draw() const override {
        return drawing_api_.DrawCircle(x_, y_, radius_);
    }

    float ResizeByPercentage(const float percent) override {
      return radius_ *= (1.0f + percent/100.0f);
    }
  
  private:
    float x_, y_, radius_;
};

int main(int argc, char** argv) {
  const DrawingAPI01 api1{};
  const DrawingAPI02 api2{};
  std::vector<CircleShape> shapes {
    CircleShape{1.0f, 2.0f, 3.0f, api1},
    CircleShape{5.0f, 7.0f, 11.0f, api2}
  }; 

  for (CircleShape& shape: shapes) {
    shape.ResizeByPercentage(2.5);
    std::println("{}", shape.Draw());
  }

  return 0;
}
</syntaxhighlight>

Output:
<pre>
API01.circle at 1.000000:2.000000 - radius: 3.075000
API02.circle at 5.000000:7.000000 - radius: 11.275000
</pre>

=== Java ===
The following [[Java (programming language)|Java]] program defines a bank account that separates the account operations from the logging of these operations. 

<syntaxhighlight lang="java">
// Logger has two implementations: info and warning
@FunctionalInterface
interface Logger {
    void log(String message);
    
    static Logger info() {
        return message -> System.out.println("info: " + message);
    }
    static Logger warning() {
        return message -> System.out.println("warning: " + message);
    }
}

abstract class AbstractAccount {
    private Logger logger = Logger.info();
    
    public void setLogger(Logger logger) {
        this.logger = logger;
    }
    
    // the logging part is delegated to the Logger implementation
    protected void operate(String message, boolean result) {
        logger.log(message + " result " + result);
    }
}

class SimpleAccount extends AbstractAccount {
    private int balance;
    
    public SimpleAccount(int balance) {
        this.balance = balance;
    }
    
    public boolean isBalanceLow() {
        return balance < 50;
    }
    
    public void withdraw(int amount) {
        boolean shouldPerform = balance >= amount;
        if (shouldPerform) {
            balance -= amount;
        }
        operate("withdraw " + amount, shouldPerform);
    }
}

public class BridgeDemo {
    public static void main(String[] args) {
        SimpleAccount account = new SimpleAccount(100);
        account.withdraw(75);
        
        if (account.isBalanceLow()) {
            // you can also change the Logger implementation at runtime
            account.setLogger(Logger.warning());
        }
        
        account.withdraw(10);
        account.withdraw(100);
    }
}
</syntaxhighlight>

It will output:
<pre>
info: withdraw 75 result true
warning: withdraw 10 result true
warning: withdraw 100 result false
</pre>

=== PHP ===
<syntaxhighlight lang="php>
interface DrawingAPI
{
    function drawCircle($x, $y, $radius);
}

class DrawingAPI1 implements DrawingAPI
{
    public function drawCircle($x, $y, $radius)
    {
        echo "API1.circle at $x:$y radius $radius.\n";
    }
}

class DrawingAPI2 implements DrawingAPI
{
    public function drawCircle($x, $y, $radius)
    {
        echo "API2.circle at $x:$y radius $radius.\n";
    }
}

abstract class Shape
{
    protected $drawingAPI;

    public abstract function draw();
    public abstract function resizeByPercentage($pct);

    protected function __construct(DrawingAPI $drawingAPI)
    {
        $this->drawingAPI = $drawingAPI;
    }
}

class CircleShape extends Shape
{
    private $x;
    private $y;
    private $radius;

    public function __construct($x, $y, $radius, DrawingAPI $drawingAPI)
    {
        parent::__construct($drawingAPI);
        $this->x = $x;
        $this->y = $y;
        $this->radius = $radius;
    }

    public function draw()
    {
        $this->drawingAPI->drawCircle($this->x, $this->y, $this->radius);
    }

    public function resizeByPercentage($pct)
    {
        $this->radius *= $pct;
    }
}

class Tester
{
    public static function main()
    {
        $shapes = array(
            new CircleShape(1, 3, 7,  new DrawingAPI1()),
            new CircleShape(5, 7, 11, new DrawingAPI2()),
        );

        foreach ($shapes as $shape) {
            $shape->resizeByPercentage(2.5);
            $shape->draw();
        }
    }
}

Tester::main();
</syntaxhighlight>

Output:
 API1.circle at 1:3 radius 17.5
 API2.circle at 5:7 radius 27.5

=== Scala ===
<syntaxhighlight lang="scala">
trait DrawingAPI {
  def drawCircle(x: Double, y: Double, radius: Double)
}

class DrawingAPI1 extends DrawingAPI {
  def drawCircle(x: Double, y: Double, radius: Double) = println(s"API #1 $x $y $radius")
}

class DrawingAPI2 extends DrawingAPI {
  def drawCircle(x: Double, y: Double, radius: Double) = println(s"API #2 $x $y $radius")
}

abstract class Shape(drawingAPI: DrawingAPI) {
  def draw()
  def resizePercentage(pct: Double)
}

class CircleShape(x: Double, y: Double, var radius: Double, drawingAPI: DrawingAPI)
    extends Shape(drawingAPI: DrawingAPI) {

  def draw() = drawingAPI.drawCircle(x, y, radius)

  def resizePercentage(pct: Double) { radius *= pct }
}

object BridgePattern {
  def main(args: Array[String]) {
    Seq (
	new CircleShape(1, 3, 5, new DrawingAPI1),
	new CircleShape(4, 5, 6, new DrawingAPI2)
    ) foreach { x =>
        x.resizePercentage(3)
        x.draw()			
      }	
  }
}
</syntaxhighlight>

===Python===
<syntaxhighlight lang="python">
"""
Bridge pattern example.
"""
from abc import ABCMeta, abstractmethod


NOT_IMPLEMENTED = "You should implement this."


class DrawingAPI:
    __metaclass__ = ABCMeta

    @abstractmethod
    def draw_circle(self, x, y, radius):
        raise NotImplementedError(NOT_IMPLEMENTED)


class DrawingAPI1(DrawingAPI):
    def draw_circle(self, x, y, radius):
        return f"API1.circle at {x}:{y} - radius: {radius}"


class DrawingAPI2(DrawingAPI):
    def draw_circle(self, x, y, radius):
        return f"API2.circle at {x}:{y} - radius: {radius}"


class DrawingAPI3(DrawingAPI):
    def draw_circle(self, x, y, radius):
        return f"API3.circle at {x}:{y} - radius: {radius}"


class Shape:
    __metaclass__ = ABCMeta

    drawing_api = None
    def __init__(self, drawing_api):
        self.drawing_api = drawing_api

    @abstractmethod
    def draw(self):
        raise NotImplementedError(NOT_IMPLEMENTED)

    @abstractmethod
    def resize_by_percentage(self, percent):
        raise NotImplementedError(NOT_IMPLEMENTED)


class CircleShape(Shape):
    def __init__(self, x, y, radius, drawing_api):
        self.x = x
        self.y = y
        self.radius = radius
        super(CircleShape, self).__init__(drawing_api)


    def draw(self):
        return self.drawing_api.draw_circle(self.x, self.y, self.radius)

    def resize_by_percentage(self, percent):
        self.radius *= 1 + percent / 100


class BridgePattern:
    @staticmethod
    def test():
        shapes = [
            CircleShape(1.0, 2.0, 3.0, DrawingAPI1()),
            CircleShape(5.0, 7.0, 11.0, DrawingAPI2()),
            CircleShape(5.0, 4.0, 12.0, DrawingAPI3()),
        ]

        for shape in shapes:
            shape.resize_by_percentage(2.5)
            print(shape.draw())


BridgePattern.test()
</syntaxhighlight>