CSC/ECE 517 Fall 2007/wiki1b 2 Method Missing - Revision history

Pmzachar: /* "Method Missing for Dummies" Example! */

2007-10-02T03:16:14Z

"Method Missing for Dummies" Example!

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	method_missing is in part a safety net: It gives you a way to intercept unanswerable messages and handle them gracefully.		method_missing is in part a safety net: It gives you a way to intercept unanswerable messages and handle them gracefully.

	~~== "Method Missing for Dummies" Example! ==~~
	~~-> http://rubylearning.com/satishtalim/ruby_method_missing.html~~

2007-10-02T03:06:11Z

"The Good" about Method Missing!

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	>> '''Lafcadio''', an object-relational mapping layer for Ruby and MySQL uses method_missing to dynamically define getters and setters for domain objects.		>> '''Lafcadio''', an object-relational mapping layer for Ruby and MySQL uses method_missing to dynamically define getters and setters for domain objects.

	>> '''Hash with Attrs''' ~~is kind of neat. Make~~ your Hashes act like JavaScript objects.		>> '''Hash with Attrs''' makes your Hashes act like JavaScript objects.

	class Hash		class Hash

2007-10-02T03:04:05Z

What is "Method Missing" and what the fuss is all about ???

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	== What is "Method Missing" and what the fuss is all about ??? ==		== What is "Method Missing" and what the fuss is all about ??? ==

	~~One of the feaures of~~ Ruby ~~that makes it~~ special is that ~~whenever~~ a call to an undefined method is made on an object, it provides an option to intercept the call. This is done by the method ~~‘method_missing’~~. In other words it is called whenever someone tries to call a method in your object that doesn't exist. Using this hook, we can "pretend" to accept method calls that aren't defined.		Ruby has a special feature that takes care of the situation when a call to an undefined method is made on an object, it provides an option to intercept the call. This is done by the method ‘'''method_missing'''’. In other words it is called whenever someone tries to call a method in your object that doesn't exist. Using this hook, we can "pretend" to accept method calls that aren't defined.

	This is especially powerful when combined with object composition. Here's an example:		This is especially powerful when combined with object composition. Here's an example:

2007-10-02T03:00:36Z

What is "Method Missing" and what the fuss is all about ???

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	end		end
	end		end


	This object "intercepts" all method calls made to it, prints out a message and forwards on the method call to an internal object using the 'send' method-- without knowing anything about the object passed to it.		This object "intercepts" all method calls made to it, prints out a message and forwards on the method call to an internal object using the 'send' method-- without knowing anything about the object passed to it.

2007-10-02T02:59:32Z

A world without "Method Missing"

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	== A world without "Method Missing" ==		== A world without "Method Missing" ==


			Imagine an object calling a method that does not exist. It will throw an exception which definitely is undesirable. Now, if there could be a method that would perform a useful operation during such occurences then, the program can be made more useful.

	== What is "Method Missing" and what the fuss is all about ??? ==		== What is "Method Missing" and what the fuss is all about ??? ==

2007-10-02T02:21:31Z

"The Good" about Method Missing!

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	>> '''Builder::XmlBase''' translates method calls into XML tags.		>> '''Builder::XmlBase''' translates method calls into XML tags.

			>> '''Lafcadio''', an object-relational mapping layer for Ruby and MySQL uses method_missing to dynamically define getters and setters for domain objects.

	>> '''Hash with Attrs''' is kind of neat. Make your Hashes act like JavaScript objects.		>> '''Hash with Attrs''' is kind of neat. Make your Hashes act like JavaScript objects.

	• class Hash		class Hash
	• def method_missing(meth,*args)		def method_missing(meth,*args)
	• if /=$/=~(meth=meth.id2name) then		if /=$/=~(meth=meth.id2name) then
	• self[meth[0...-1]] = (args.length<2 ? args[0] : args)		self[meth[0...-1]] = (args.length<2 ? args[0] : args)
	• else		else
	• self[meth]		self[meth]
	• end		end
	• end		end
	• end		end

	~~>> Lafcadio, an object-relational mapping layer for Ruby and MySQL uses method_missing to dynamically define getters and setters for domain objects.~~

	== "The Bad" about Method Missing! ==		== "The Bad" about Method Missing! ==

2007-10-02T02:19:31Z

"The Good" about Method Missing!

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	== A world without "Method Missing" ==		== A world without "Method Missing" ==

2007-10-02T02:18:44Z

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	"There are plenty of examples of method_missing on the Web. Unfortunately, I find most of them rather difficult to understand. One needs to look at quite a bit of source code and figure out what it does. Fix this by giving a plain-English description of several uses of method_missing not covered in our class, with Web links to the pages where you found them."


	== A world without "Method Missing" ==		== A world without "Method Missing" ==

2007-10-02T02:17:33Z

"The Good" about Method Missing!

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	== "The Good" about Method Missing! ==		== "The Good" about Method Missing! ==

			>> '''XMLRPC::Client::Proxy''' will pass its method calls directly onto the service. You can even specify a prefix, which makes the whole thing a little more psuedo-OO.

			>> '''Builder::XmlBase''' translates method calls into XML tags.

			>> '''Hash with Attrs''' is kind of neat. Make your Hashes act like JavaScript objects.

			• class Hash
			• def method_missing(meth,*args)
			• if /=$/=~(meth=meth.id2name) then
			• self[meth[0...-1]] = (args.length<2 ? args[0] : args)
			• else
			• self[meth]
			• end
			• end
			• end

			>> Lafcadio, an object-relational mapping layer for Ruby and MySQL uses method_missing to dynamically define getters and setters for domain objects.

	== "The Bad" about Method Missing! ==		== "The Bad" about Method Missing! ==

2007-10-02T02:07:20Z

What is "Method Missing" and what the fuss is all about ???

← Older revision		Revision as of 02:07, 2 October 2007
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	This object "intercepts" all method calls made to it, prints out a message and forwards on the method call to an internal object using the 'send' method-- without knowing anything about the object passed to it.		This object "intercepts" all method calls made to it, prints out a message and forwards on the method call to an internal object using the 'send' method-- without knowing anything about the object passed to it.

			method_missing is in part a safety net: It gives you a way to intercept unanswerable messages and handle them gracefully.

	== "Method Missing for Dummies" Example! ==		== "Method Missing for Dummies" Example! ==