设计模式之Adapter

#设计模式 #Ruby #Objective-C

适配器模式的百度百科解释:

在计算机编程中，适配器模式（有时候也称包装样式或者包装）将一个类的接口适配成用户所期待的。一个适配允许通常因为接口不兼容而不能在一起工作的类工作在一起，做法是将类自己的接口包裹在一个已存在的类中。

简单的说，就是需要的东西就在面前，但却不能使用，而短时间又无法改造它，于是我们就想办法适配它。

1.Objetive-C 中的实现

Target.h

#import <Foundation/Foundation.h>                 

@interface Target:NSObject

-(void)request;

@end

Target.m

#import "Target.h"
           
@implementation Target             

-(void)request
{
    NSLog(@"普通请求！");
}

@end

Adaptee.h

#import <Foundation/Foundation.h>             

@interface Adaptee:NSObject             

-(void)specificRequest;

@end

Adaptee.m

#import "Adaptee.h"

@implementation Adaptee

-(void)specificRequest 
{
    NSLog(@"特殊请求！");
}

@end

Adapter.h

#import "Target.h"

@class Adaptee;

@interface Adapter : Target {
    Adaptee *_adaptee;
}

-(id)initWithAdaptee:(Adaptee *)adaptee;

@end

Adapter.m

#import "Adapter.h"
#import "Adaptee.h"

@implementation Adapter

-(id)initWithAdaptee:(Adaptee *)adaptee
{
    if (self = [super init]) {
        _adaptee = adaptee;
    }

    return self;
}

-(void)request 
{
    [_adaptee specificRequest];
}

@end

使用:

Adaptee *adaptee = [[Adaptee alloc] init];
Adapter *adapter = [[Adapter alloc] initWithAdaptee:adaptee];
[adapter request];

2.Ruby中的实现

Renderer 可直接渲染 TextObject 类，而 BritishTextObject 类具有不一样的接口。要使 Renderer 类也渲染 BritishTextObject 类，则需要设计兼容的适配器 BritishTextObjectAdapter:

class Renderer
  def render(text_object)
    text = text_object.text
    size = text_object.size
    puts "text:#{text}, size:#{size}\n"
  end
end

class TextObject
  attr_reader :text, :size
  
  def initialize(text, size)
    @text = text
    @size = size
  end
end

class BritishTextObject
  attr_reader :string, :length
  
  def initialize(string, size_mm)
    @string = string
    @size_mm = size_mm
  end
end

class BritishTextObjectAdapter < TextObject
  def initialize(british_text_object)
    @british_text_object = british_text_object
  end
  
  def text
    return @british_text_object.string
  end
  
  def size
    return @british_text_object.size_mm/25.4
  end
end

Renderer.new.render(TextObject.new("TextObject", 15)) 
Renderer.new.render(BritishTextObjectAdapter.new(BritishTextObject.new("BritishObject", 15)))