Eloquent Ruby 读书笔记 续

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Eloquent Ruby 读书笔记 续

initializeruby
运算符重载和Ruby风格的运算符重载
程序大概意思是，重新定义，文件类的比较方法。只要目录和文件名一样，就说这两个文件类一样。ruby的
Ruby代码

1. class DocumentPointer   
   
2.   attr_reader :folder, :name  
   
3.   def initialize( folder, name )   
   
4.     @folder = folder   
   
5.     @name = name   
   
6.   end  
   
7.   def ==(other)   
   
8.     return true if other.equal?(self)   
   
9.     return false unless other.instance_of?(self.class)   
   
10.     folder == other.folder && name == other.name   
    
11.   end  
    
12. end  
    
13. 
    
14. class DocumentPointer
    
15.   attr_reader :folder, :name
    
16.   def initialize( folder, name )
    
17.     @folder = folder
    
18.     @name = name
    
19.   end
    
20.   def ==(other)
    
21.     return true if other.equal?(self)
    
22.     return false unless other.instance_of?(self.class)
    
23.     folder == other.folder && name == other.name
    
24.   end
    
25. end

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Ruby代码

1. class DocumentPointer   
   
2.   attr_reader :folder, :name  
   
3.   def initialize( folder, name )   
   
4.     @folder = folder   
   
5.     @name = name   
   
6.   end  
   
7.   def ==(other)   
   
8.     return false unless other.respond_to?(:folder)   
   
9.     return false unless other.respond_to?(:name)   
   
10.     folder == other.folder && name == other.name   
    
11.   end  
    
12. end  
    
13. 
    
14. class DocumentPointer
    
15.   attr_reader :folder, :name
    
16.   def initialize( folder, name )
    
17.     @folder = folder
    
18.     @name = name
    
19.   end
    
20.   def ==(other)
    
21.     return false unless other.respond_to?(:folder)
    
22.     return false unless other.respond_to?(:name)
    
23.     folder == other.folder && name == other.name
    
24.   end
    
25. end

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当我们用的时候
Ruby代码

1. #Asymmetry   
   
2. class ContractIdentifier < DocumentIdentifier   
   
3. end  
   
4.   
   
5. doc_id = DocumentIdentifier.new( 'contracts', 'Book Deal' )   
   
6. con_id = ContractIdentifier.new( 'contracts', 'Book Deal' )   
   
7.   
   
8. puts "They are equal!" if doc_id == con_id  
   
9. 
   
10. #Asymmetry
    
11. class ContractIdentifier < DocumentIdentifier
    
12. end
    
13. 
    
14. doc_id = DocumentIdentifier.new( 'contracts', 'Book Deal' )
    
15. con_id = ContractIdentifier.new( 'contracts', 'Book Deal' )
    
16. 
    
17. puts "They are equal!" if doc_id == con_id

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会出现子类没有父类方法的问题，在contractIdentifier里没有重载操作符。那么

Ruby代码

1. class VersionedIdentifier < DocumentIdentifier   
   
2.   attr_reader :version  
   
3.   
   
4.   def initialize(folder, name, version)   
   
5.     super(folder, name)   
   
6.     Well-Behaved Equality 147   
   
7.     @version = version   
   
8.   end  
   
9.   
   
10.   def ==(other)   
    
11.     if other.instance_of? VersionedIdentifier   
    
12.       other.folder == folder &&   
    
13.       other.name == name &&   
    
14.       other.version == version   
    
15.     elsif other.instance_of? DocumentIdentifier   
    
16.       other.folder == folder && other.name == name   
    
17.     else  
    
18.       false  
    
19.     end  
    
20.   end  
    
21. end  

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小忻黑夜

谢谢分享