Class: MethodProxy

Inherits:
Object
  • Object
show all
Defined in:
lib/method_proxy.rb

Constant Summary collapse

@@mx =

CLASS VARIABLES #############################################

Mutex.new
@@proxied_instance_methods = 
{}
@@proxied_class_methods = 
{}
@@tmp_binding = 
nil

Class Method Summary collapse

Class Method Details

.classes_with_proxied_class_methods ⇒ Object 



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# File 'lib/method_proxy.rb', line 32

def self.classes_with_proxied_class_methods
  @@mx.synchronize do
    return @@proxied_class_methods.keys.collect{|k| Class.const_get(k)}
  end
end

.classes_with_proxied_instance_methods ⇒ Object

SOME HELPER METHODS ##########################################



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# File 'lib/method_proxy.rb', line 16

def self.classes_with_proxied_instance_methods
  @@mx.synchronize do
    return @@proxied_instance_methods.keys.collect{|k| Class.const_get(k)}
  end
end

.original_instance_method(klass, meth_name) ⇒ Object 



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# File 'lib/method_proxy.rb', line 54

def self.original_instance_method(klass, meth_name)
  @@proxied_instance_methods[klass.name.to_sym][meth_name]
end

.proxied_class_methods_for(klass) ⇒ Object 



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# File 'lib/method_proxy.rb', line 38

def self.proxied_class_methods_for(klass)
  raise "klass argument must be a Class" unless klass.is_a?(Class) || klass.is_a?(Module)
  @@mx.synchronize do
    meth_hash_for_klass = @@proxied_class_methods[klass.name.to_sym]
    return [] if !meth_hash_for_klass || meth_hash_for_klass.empty?
    return meth_hash_for_klass.keys
  end
end

.proxied_instance_methods_for(klass) ⇒ Object 



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# File 'lib/method_proxy.rb', line 22

def self.proxied_instance_methods_for(klass)
  raise "klass argument must be a Class" unless klass.is_a?(Class) || klass.is_a?(Module)
  @@mx.synchronize do
    meth_hash_for_klass = @@proxied_instance_methods[klass.name.to_sym]
    return [] if !meth_hash_for_klass || meth_hash_for_klass.empty?
    return meth_hash_for_klass.keys
  end
end

.proxy_class_method(klass, meth, &block) ⇒ Object

“Tap” into class method calls - subvert original method with the supplied block; preserve reference to the original method so that it can still be called or restored later on.

Common idiom: MethodProxy.proxy_class_method(SomeClass, :some_class_method) do |klass, original_class_meth, *args, &block|

# do stuff before calling original method
  ... ... ...

# call original method (already bound to SomeClass), with supplied arguments
result = original_class_meth.call(*args, &block)

# do stuff after calling original method
  ... ... ...

# return the actual return value
result

end



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# File 'lib/method_proxy.rb', line 155

def self.proxy_class_method klass, meth, &block
  raise "klass argument must be a Class" unless klass.is_a?(Class) || klass.is_a?(Module)
  raise "method argument must be a Symbol" unless meth.is_a?(Symbol)
  raise "must supply block argument" unless block_given?
  
  @@mx.synchronize do
    proc = Proc.new(&block)
    
    capture_tmp_binding! binding
    
    @@proxied_class_methods[klass.name.to_sym] ||= {}
  
    class << klass
      
      klass, meth, proc = eval "[klass, meth, proc]", MethodProxy.tmp_binding
      
      self.instance_eval do
        if @@proxied_class_methods[klass.name.to_sym][meth]
          raise ::MethodProxyException, "The method has already been proxied"
        end
        @@proxied_class_methods[klass.name.to_sym][meth] = instance_method meth
      end
    
      remove_method meth
    
      self.instance_eval do
        define_method(meth) do |*args, &blk|
          ret = proc.call(self, @@proxied_class_methods[klass.name.to_sym][meth].bind(self), *args, &blk)
          return ret
        end
      end
    end
    
    reset_tmp_binding!
  end
end

.proxy_instance_method(klass, meth, &block) ⇒ Object

“Tap” into instance method calls - subvert original method with the supplied block; preserve reference to the original method so that it can still be called or restored later on.

Common idiom: MethodProxy.proxy_instance_method(SomeClass, :some_instance_method) do |obj, original_instance_meth, *args, &block|

# do stuff before calling original method
  ... ... ...

# call the original method (already bound to object obj), with supplied arguments
result = original_instance_meth.call(*args, &block)

# do stuff after calling original method
  ... ... ...

# return the actual return value
result

end



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# File 'lib/method_proxy.rb', line 92

def self.proxy_instance_method(klass, meth, &block)
  raise "klass argument must be a Class" unless klass.is_a?(Class) || klass.is_a?(Module)
  raise "method argument must be a Symbol" unless meth.is_a?(Symbol)
  raise "must supply block argument" unless block_given?
  
  proc = Proc.new(&block)
  
  @@mx.synchronize do
    @@proxied_instance_methods[klass.name.to_sym] ||= {}
    if @@proxied_instance_methods[klass.name.to_sym][meth]
      raise ::MethodProxyException, "The method has already been proxied"
    end
  
    klass.class_eval do
    
      MethodProxy.register_original_instance_method(klass, meth, instance_method(meth))
    
      undef_method(meth)
  
      define_method meth do |*args, &blk|
        ret = proc.call(self, MethodProxy.original_instance_method(klass, meth).bind(self), *args, &blk)
        return ret
      end
    end
  end
end

.register_original_instance_method(klass, meth_name, meth_obj) ⇒ Object

WARNING: NON-THREAD-SAFE methods for internal use; generally, they should not be called by ####

any external code                                          ####



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# File 'lib/method_proxy.rb', line 50

def self.register_original_instance_method(klass, meth_name, meth_obj)
  @@proxied_instance_methods[klass.name.to_sym][meth_name] = meth_obj
end

.tmp_binding ⇒ Object 



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# File 'lib/method_proxy.rb', line 58

def self.tmp_binding
  @@tmp_binding
end

.unproxy_class_method(klass, meth) ⇒ Object

Restore the original class method for klass



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# File 'lib/method_proxy.rb', line 193

def self.unproxy_class_method klass, meth
  raise "klass argument must be a Class" unless klass.is_a?(Class) || klass.is_a?(Module)
  raise "method argument must be a Symbol" unless meth.is_a?(Symbol)
  
  @@mx.synchronize do
    return unless (class_entries = @@proxied_class_methods[klass.name.to_sym])
    return unless (orig_unbound_meth = class_entries[meth])
  
    capture_tmp_binding! binding
  
    class << klass
      meth, orig_unbound_meth = eval "[meth, orig_unbound_meth]", MethodProxy.tmp_binding
      self.instance_eval do
        define_method meth, orig_unbound_meth
      end
    end
    
    reset_tmp_binding!
    
    # clean up storage
    @@proxied_class_methods[klass.name.to_sym].delete(meth)
    remaining_proxied_class_methods = @@proxied_class_methods[klass.name.to_sym]
    @@proxied_class_methods.delete(klass.name.to_sym) if remaining_proxied_class_methods.empty?
  end
end

.unproxy_instance_method(klass, meth) ⇒ Object

Restore the original instance method for objects of class klass



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# File 'lib/method_proxy.rb', line 120

def self.unproxy_instance_method(klass, meth)
  raise "klass argument must be a Class" unless klass.is_a?(Class) || klass.is_a?(Module)
  raise "method argument must be a Symbol" unless meth.is_a?(Symbol)
  
  @@mx.synchronize do
    return unless @@proxied_instance_methods[klass.name.to_sym][meth].is_a?(UnboundMethod)    # pass-through rather than raise
    proc = @@proxied_instance_methods[klass.name.to_sym][meth]
  
    klass.class_eval{ define_method(meth, proc) }
    
    # clean up storage
    @@proxied_instance_methods[klass.name.to_sym].delete(meth)
    remaining_proxied_instance_methods = @@proxied_instance_methods[klass.name.to_sym]
    @@proxied_instance_methods.delete(klass.name.to_sym) if remaining_proxied_instance_methods.empty?
  end
end