适配器模式 - 设计模式系列

适配器模式，用于连接两种不同种类的对象，使其协同工作。一边是客户端懂得如何使用的目标接口，另一边是客户端一无所知的被适配者。适配器的主要作用是把被适配者的行为传递给管道另一端的客户端。

核心代码：

 //
 //  StrokeColorCommand.h
 //  TouchPainter
 //
 //  Created by Carlo Chung on 11/9/10.
 //  Copyright 2010 Carlo Chung. All rights reserved.
 //

 #import <Foundation/Foundation.h>
 #import "Command.h"

 typedef void (^RGBValuesProvider)(CGFloat *red, CGFloat *green, CGFloat *blue);
 typedef void (^PostColorUpdateProvider)(UIColor *color);

 @class SetStrokeColorCommand;

 @protocol SetStrokeColorCommandDelegate

 - (void) command:(SetStrokeColorCommand *) command
                 didRequestColorComponentsForRed:(CGFloat *) red
                                           green:(CGFloat *) green
                                            blue:(CGFloat *) blue;

 - (void) command:(SetStrokeColorCommand *) command
                 didFinishColorUpdateWithColor:(UIColor *) color;

 @end


 @interface SetStrokeColorCommand : Command
 {
   @private
   id <SetStrokeColorCommandDelegate> delegate_;
   RGBValuesProvider RGBValuesProvider_;
   PostColorUpdateProvider postColorUpdateProvider_;
 }

 @property (nonatomic, assign) id <SetStrokeColorCommandDelegate> delegate;
 @property (nonatomic, copy) RGBValuesProvider RGBValuesProvider;
 @property (nonatomic, copy) PostColorUpdateProvider postColorUpdateProvider;

 - (void) execute;

 @end

 //
 //  StrokeColorCommand.h
 //  TouchPainter
 //
 //  Created by Carlo Chung on 11/9/10.
 //  Copyright 2010 Carlo Chung. All rights reserved.
 //

 #import <Foundation/Foundation.h>
 #import "Command.h"

 typedef void (^RGBValuesProvider)(CGFloat *red, CGFloat *green, CGFloat *blue);
 typedef void (^PostColorUpdateProvider)(UIColor *color);

 @class SetStrokeColorCommand;

 @protocol SetStrokeColorCommandDelegate

 - (void) command:(SetStrokeColorCommand *) command
                 didRequestColorComponentsForRed:(CGFloat *) red
                                           green:(CGFloat *) green
                                            blue:(CGFloat *) blue;

 - (void) command:(SetStrokeColorCommand *) command
                 didFinishColorUpdateWithColor:(UIColor *) color;

 @end


 @interface SetStrokeColorCommand : Command
 {
   @private
   id <SetStrokeColorCommandDelegate> delegate_;
   RGBValuesProvider RGBValuesProvider_;
   PostColorUpdateProvider postColorUpdateProvider_;
 }

 @property (nonatomic, assign) id <SetStrokeColorCommandDelegate> delegate;
 @property (nonatomic, copy) RGBValuesProvider RGBValuesProvider;
 @property (nonatomic, copy) PostColorUpdateProvider postColorUpdateProvider;

 - (void) execute;

 @end

 //
 //  StrokeColorCommand.m
 //  TouchPainter
 //
 //  Created by Carlo Chung on 11/9/10.
 //  Copyright 2010 Carlo Chung. All rights reserved.
 //

 #import "SetStrokeColorCommand.h"
 #import "CoordinatingController.h"
 #import "CanvasViewController.h"

 @implementation SetStrokeColorCommand

 @synthesize delegate=delegate_;
 @synthesize postColorUpdateProvider=postColorUpdateProvider_;
 @synthesize RGBValuesProvider=RGBValuesProvider_;


 - (void) execute
 {
   CGFloat redValue = 0.0;
   CGFloat greenValue = 0.0;
   CGFloat blueValue = 0.0;

   // Retrieve RGB values from a delegate or a block

   // Delegation (object adapter) approach:
   [delegate_ command:self didRequestColorComponentsForRed:&redValue
                                                     green:&greenValue
                                                      blue:&blueValue];

   // Block approach:
   if (RGBValuesProvider_ != nil)
   {
     RGBValuesProvider_(&redValue, &greenValue, &blueValue);
   }

   // Create a color object based on the RGB values
   UIColor *color = [UIColor colorWithRed:redValue
                                    green:greenValue
                                     blue:blueValue
                                    alpha:1.0];

   // Assign it to the current canvasViewController
   CoordinatingController *coordinator = [CoordinatingController sharedInstance];
   CanvasViewController *controller = [coordinator canvasViewController];
   [controller setStrokeColor:color];

   // Forward a post update message

   // Delegation approach:
   [delegate_ command:self didFinishColorUpdateWithColor:color];

   // Block approach:
   if (postColorUpdateProvider_ != nil)
   {
     postColorUpdateProvider_(color);
   }
 }

 - (void) dealloc
 {
   [RGBValuesProvider_ release];
   [postColorUpdateProvider_ release];
   [super dealloc];
 }

 @end

 // Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
 - (void)viewDidLoad
 {
   [super viewDidLoad];

   // initialize the RGB sliders with
   // a StrokeColorCommand
   SetStrokeColorCommand *colorCommand = (SetStrokeColorCommand *)[redSlider_ command];

   // set each color component provider
   // to the color command
   [colorCommand setRGBValuesProvider: ^(CGFloat *red, CGFloat *green, CGFloat *blue)
    {
      *red = [redSlider_ value];
      *green = [greenSlider_ value];
      *blue = [blueSlider_ value];
    }];

   // set a post-update provider to the command
   // for any callback after a new color is set
   [colorCommand setPostColorUpdateProvider: ^(UIColor *color)
    {
      [paletteView_ setBackgroundColor:color];
    }];


   // restore the original values of the sliders
   // and the color of the small palette view
   NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
   CGFloat redValue = [userDefaults floatForKey:@"red"];
   CGFloat greenValue = [userDefaults floatForKey:@"green"];
   CGFloat blueValue = [userDefaults floatForKey:@"blue"];
   CGFloat sizeValue = [userDefaults floatForKey:@"size"];

   [redSlider_ setValue:redValue];
   [greenSlider_ setValue:greenValue];
   [blueSlider_ setValue:blueValue];
   [sizeSlider_ setValue:sizeValue];

   UIColor *color = [UIColor colorWithRed:redValue
                                    green:greenValue
                                     blue:blueValue
                                    alpha:1.0];

   [paletteView_ setBackgroundColor:color];
 }


 #pragma mark -
 #pragma mark SetStrokeColorCommandDelegate methods

 - (void) command:(SetStrokeColorCommand *) command
                 didRequestColorComponentsForRed:(CGFloat *) red
                                           green:(CGFloat *) green
                                            blue:(CGFloat *) blue
 {
   *red = [redSlider_ value];
   *green = [greenSlider_ value];
   *blue = [blueSlider_ value];
 }

参考 《Object-C 编程之道 iOS设计模式解析》

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