红宝石 |访问控制

访问控制是面向对象编程语言中非常重要的一部分，用于限制方法和成员字段的可见性，以保护数据不被意外修改。在访问控制方面，Ruby 不同于所有其他面向对象的编程语言。

关于 Ruby 访问控制的要点：

类变量和实例的可见性始终是私有的。
访问控制仅适用于方法。
我们不能对实例和类变量应用任何访问控制。
Ruby 中的私有方法也可以像公共和受保护方法一样被继承。

在 Ruby 中，访问控制在两个条件下起作用：

首先，从哪里调用方法，即在类定义的内部或外部。
其次，是否包含self关键字。基本上，self-keyword 用于指向当前收件人。

在 Ruby 中，继承没有必要参与访问控制，就像在 C++ 中，访问控制在继承中使用。访问控制分为三种类型，如下图所示：

公共方法

公共方法是任何人都可以调用的方法。正如我们所知，访问控制仅适用于方法，因此默认情况下所有方法都是 public 。但是，我们仍然可以使用public关键字显式定义公共方法。公共方法通常在类外调用。

例子：

# Ruby program to demonstrate 
# the public access control
  
#!/usr/bin/ruby
  
# taking a class
class GeeksforGeeks
  
     # public method without using 
     # public keyword    
     def geeks_1
         puts "public method geeks_1 is called"
     end
  
    # using public keyword
    public
     
     def geeks_2
         puts "public method geeks_2 is called"  
     end
       
     def geeks_3
           
         puts "public method geeks_3 is called"
           
         # calling geeks_1 method
         geeks_1
           
         # calling geeks_1 method using
         # self-keyword
         self.geeks_1
     end          
end
  
# creating the object of 
# class GeeksforGeeks
obj = GeeksforGeeks.new
  
# calling method geeks_1
obj.geeks_1
  
# calling method geeks_2
obj.geeks_2
  
# calling method geeks3
obj.geeks_3

输出：

public method geeks_1 is called
public method geeks_2 is called
public method geeks_3 is called
public method geeks_1 is called
public method geeks_1 is called

私有方法

私有方法是那些在类外部无法访问的方法，或者换句话说，私有方法只能在类定义内部调用。类的方法可以访问私有成员。在私有方法中，我们不使用 self 关键字。默认情况下，初始化方法将是私有方法。用户不能将初始化方法设为公共方法。私有方法是使用private关键字定义的。

注意：众所周知，私有方法的可见性受到严格限制，只有定义的类成员才能访问这些方法，但它们可以被子类继承。子类可以访问它们并且可以覆盖它们。

例子：

# Ruby program to demonstrate 
# the private access control
  
#!/usr/bin/ruby
  
# creating class
class GeeksforGeeks
       
    # using initialize method
    # it can't be private
    def initialize
        puts "This is the initialize Method"
     end
      
    # public method
    def geeks_1
          
             puts "Public geeks_1 Method"
         end
      
    # using the private keyword to 
    # declare a private method
    private
      
     def geeks_2
           
         puts "This is Private Method"  
     end 
       
end          
  
# creating the object of 
# the class GeeksforGeeks
obj = GeeksforGeeks.new
  
# calling method geeks_1
# (geeks1 method is public method)
obj.geeks_1
  
# calling private method will give the error
obj.geeks_2

错误：

source_file.rb:41:in `

‘: private method `geeks_2’ called for #<0x00000001ecc9e8> (NoMethodError)
Did you mean? geeks_1

This is the initialize Method
Public geeks_1 Method

0x00000001ecc9e8>

编程需要懂一点英语

受保护的方法

受保护的方法只能被定义的类及其子类的对象调用。这些方法的访问被限制在定义的类或其子类之间。您不能访问已定义类或其子类之外的受保护方法。受保护方法的使用是有限的。受保护的方法是使用受保护的关键字定义的。

例子：

# Ruby program to demonstrate 
# the protected access control
  
#!/usr/bin/ruby
  
class GeeksforGeeks
    
    # using initialize method
    def initialize
          
        # calling geeks_2 method
        geeks_2
          
        # calling geeks_2 method 
        # using self-keyword
        self.geeks_2
          
     end
      
    # public method
    def geeks_1
         puts " geeks_1 method is called"  
     end 
      
    # defining the protected method using
    # protected keyword
    protected
      
    def geeks_2
         puts " geeks_2 method is called"  
    end
  
end
  
# creating the object of class GeeksforGeeks
obj = GeeksforGeeks.new
  
# calling method
obj.geeks_1
  
  
# if you will try to call protected method 
# using the object of class then it will 
# give error
obj.geeks_2

错误：

source_file.rb:45:in `

‘: protected method `geeks_2’ called for #<0x00000000b14a18> (NoMethodError)
Did you mean? geeks_1

geeks_2 method is called
geeks_2 method is called
geeks_1 method is called

0x00000000b14a18>

编程需要懂一点英语

笔记：

用户可以在同一类的公共方法中调用私有方法和受保护方法。

例子：

# Ruby program to demonstrate the calling 
# of private and protected method in the 
# public method
  
class Geeks
   
    # public method
    def method_1
    
     p "Public Method of class Geeks"
       
        # calling protected and private method
        # inside the public method
        method_2
        method_3
    end
   
    # defining the protected method
    protected
   
    def method_2
          
        p "Protected Method of class Geeks"
     end
   
    # defining the private method   
    private
   
    def method_3
          
       p "Private Method of class Geeks"
          
     end
end
   
# creating an object of class Geeks
obj = Geeks.new
  
# calling the public method of class Geeks
obj.method_1

输出：

"Public Method of class Geeks"
"Protected Method of class Geeks"
"Private Method of class Geeks"

一般来说，私有方法不能在面向对象的编程语言中被继承。但在 Ruby 中，私有方法也可以像受保护和公共方法一样被继承。

例子：

# Ruby program to demonstrate that private  
# method can also be inherited
  
class Geeks
   
    # public method
    def method_1
    
        p "Public Method of class Geeks"
     
    end
   
    # defining the protected method
    protected
   
    def method_2
          
        p "Protected Method of class Geeks"
     end
   
    # defining the private method   
    private
   
    def method_3
          
        p "Private Method of class Geeks"
          
     end
end
  
# Sudo class inheriting Geeks class
class Sudo < Geeks
     
    # public method of Sudo class
    def method_4
          
        p "Public Method of Sudo Class"
          
        # calling all three methods 
        # of Geeks class
        method_1
        method_2
        method_3
    end
end
   
# creating an object of class Sudo
obj_sudo = Sudo.new
  
# calling the public method
# of class Sudo which will
# automatically call the private 
# and protected method of Geeks class
obj_sudo.method_4

输出：

"Public Method of Sudo Class"
"Public Method of class Geeks"
"Protected Method of class Geeks"
"Private Method of class Geeks"

公共方法可以在定义它们的类之外访问。但是用户无法访问定义它们的类之外的私有和受保护方法。

例子：

# Ruby program to demonstrate that private  
# and protected method can't be accessed 
# outside the class even after inheritance
  
class Geeks
   
    # public method
    def method_1
    
        p "Public Method of class Geeks"
     
    end
   
    # defining the protected method
    protected
   
    def method_2
          
        p "Protected Method of class Geeks"
     end
   
    # defining the private method   
    private
   
    def method_3
          
        p "Private Method of class Geeks"
          
     end
end
  
# Sudo class inheriting Geeks class
class Sudo < Geeks
     
    # public method of Sudo class
    def method_4
          
        p "Public Method of Sudo Class"
          
    end
end
   
# creating an object of class Sudo
obj_sudo = Sudo.new
  
# calling the public method
# of class Sudo and Geeks
obj_sudo.method_4
obj_sudo.method_1
  
# if you will try to call the protected
# and private method using the object 
# of class Sudo, then it will give error
obj_sudo.method_2
obj_sudo.method_3

错误：

source_file.rb:54:in `

‘: protected method `method_2’ called for #<0x000000016e40a0> (NoMethodError)
Did you mean? method
method_1
method_4
methods

“Public Method of Sudo Class”
“Public Method of class Geeks”

0x000000016e40a0>

编程需要懂一点英语

受保护方法和私有方法之间的主要区别在于，受保护方法可以通过使用显式接收器从类内部访问，而私有方法则不能。

例子：

# Ruby program to demonstrate that private  
# and protected method can't be accessed 
# outside the class even after inheritance
  
class Geeks
   
    # public method
    def method_1
    
        p "Public Method of class Geeks"
     
    end
   
    # defining the protected method
    protected
   
    def method_2
          
        p "Protected Method of class Geeks"
     end
   
    # defining the private method   
    private
   
    def method_3
          
        p "Private Method of class Geeks"
          
     end
end
  
# Sudo class inheriting Geeks class
class Sudo < Geeks
     
    # public method of Sudo class
    def method_4
          
        p "Public Method of Sudo Class"
          
      
      
        # calling the public method 
        # of Geeks class
        method_1
  
        # creating object of class Sudo
        # inside the public method of 
        # class Sudo
        obj_inside_sudo = Sudo.new
  
        # calling the protected  
        # method of class Geeks
        obj_inside_sudo.method_2
          
        # calling the private  
        # method of class Geeks
        # using an explicit receiver
        obj_inside_sudo.method_3 rescue p "You can't Access!" 
       
  
          
    end
end
   
  
  
# creating an object of class Sudo
obj_sudo = Sudo.new
  
# calling the public method
# of class Sudo 
obj_sudo.method_4

输出：

"Public Method of Sudo Class"
"Public Method of class Geeks"
"Protected Method of class Geeks"
"You can't Access!"

要在单个类中定义多个受保护和私有方法，可以使用以下语法：

class class_name

  # this method is public 
  def public_method        
  end  

  public :method_1
  
  protected :method_2, :method_3
  
  private :method_4, :method_5  

end