类 Object

公共实例方法

DelegateClass(superclass, &block) 点击切换源代码

此库的主要接口。在定义类时使用它来设置委托。

class MyClass < DelegateClass(ClassToDelegateTo) # Step 1
  def initialize
    super(obj_of_ClassToDelegateTo)              # Step 2
  end
end

或

MyClass = DelegateClass(ClassToDelegateTo) do    # Step 1
  def initialize
    super(obj_of_ClassToDelegateTo)              # Step 2
  end
end

这里有一个来自 Tempfile 的使用示例，它实际上是一个 File 对象，有一些关于存储位置和何时删除该 File 的特殊规则。这构成了一个关于如何使用委托的几乎完美的教科书例子。

class Tempfile < DelegateClass(File)
  # constant and class member data initialization...

  def initialize(basename, tmpdir=Dir::tmpdir)
    # build up file path/name in var tmpname...

    @tmpfile = File.open(tmpname, File::RDWR|File::CREAT|File::EXCL, 0600)

    # ...

    super(@tmpfile)

    # below this point, all methods of File are supported...
  end

  # ...
end

调用父类方法

# File delegate.rb, line 394
def DelegateClass(superclass, &block)
  klass = Class.new(Delegator)
  ignores = [*::Delegator.public_api, :to_s, :inspect, :=~, :!~, :===]
  protected_instance_methods = superclass.protected_instance_methods
  protected_instance_methods -= ignores
  public_instance_methods = superclass.public_instance_methods
  public_instance_methods -= ignores
  klass.module_eval do
    def __getobj__ # :nodoc:
      unless defined?(@delegate_dc_obj)
        return yield if block_given?
        __raise__ ::ArgumentError, "not delegated"
      end
      @delegate_dc_obj
    end
    def __setobj__(obj)  # :nodoc:
      __raise__ ::ArgumentError, "cannot delegate to self" if self.equal?(obj)
      @delegate_dc_obj = obj
    end
    protected_instance_methods.each do |method|
      define_method(method, Delegator.delegating_block(method))
      protected method
    end
    public_instance_methods.each do |method|
      define_method(method, Delegator.delegating_block(method))
    end
  end
  klass.define_singleton_method :public_instance_methods do |all=true|
    super(all) | superclass.public_instance_methods
  end
  klass.define_singleton_method :protected_instance_methods do |all=true|
    super(all) | superclass.protected_instance_methods
  end
  klass.define_singleton_method :instance_methods do |all=true|
    super(all) | superclass.instance_methods
  end
  klass.define_singleton_method :public_instance_method do |name|
    super(name)
  rescue NameError
    raise unless self.public_instance_methods.include?(name)
    superclass.public_instance_method(name)
  end
  klass.define_singleton_method :instance_method do |name|
    super(name)
  rescue NameError
    raise unless self.instance_methods.include?(name)
    superclass.instance_method(name)
  end
  klass.module_eval(&block) if block
  return klass
end