ruby metaprogramming send

There are some well-known tools based on the Ruby DSL, Chef and Puppet for DevOps peoples. The answers are in the StringInquirer class, which is a subclass of String. And how does that work? This is what the code looks like: This is saying: “If the method name ends with a question mark then do the c… As the definition from Wikipedia mentioned, metaprogramming can also involve modifying in realtime the code... something we'll touch on in a later article. Another aspect of metaprogramming that Ruby gives us is the ability to generate new code during runtime. This Ruby style guide recommends best practices so that real-world Ruby programmers can write code that can be maintained by other real-world Ruby programmers. Ruby knows that method_missing( ) is there, because it's an instance method of Kernel that every object inherits. It’s not science-fiction, it’s Ruby metaprogramming! With Ruby you can modify the structure of the program in execution time. The method_missing( ) method is passed the symbol of the non-existent method, an array of the arguments that were passed in the original call and any block passed to the original method. We can take a lot of if/elsif code and use send to simplify it into one call like so: In ruby you can add methods to existing instances of any class. You can wait literally until the very last moment to decide which method to call, while the code is running. Well done. In Ruby, this can be done another way, by using the send method: "Roberto Alomar".send(:downcase) # => "roberto alomar" Generally you wouldn’t use this form in normal programming, but because Ruby allows us to send messages (or invoke methods) in this form, it gives the option of sending a dynamic message or calling methods dynamically. Ruby Metaprogramming Study Note Try to hack the Sample Apps! The first argument in send() is the message that you're sending to the object - that is, the name of a method. Then arguments those need to pass in method, those will be the remaining arguments in send(). To remove existing methods, you can use the remove_method within the scope of a given class. method that ruby gives you access inside of your objects a way to handle situations when you call a method that doesn't exist In all honesty that is a fair question, and please excuse the low quality attempt at finding a picture of a cuttle fish with a ruby on its head to satisfy my own desires. Why is that a big deal? The Module#define_method( ) is a private instance method of the class Module. To understand the concept of an ancestors chain, just look at any Ruby class. Note: The material in these study notes is drawn primarily from the references mentioned on the last page. @MattStopa on twittermattstopa.com on the webThe video in a series of videos on Ruby Metaprogramming. It could be string or symbol but symbols are preferred. For example: The respond_to? The path of classes you just traversed is called the "ancestors chain" of the class (the ancestors chain also includes modules). # --------- Meta Programing way --------------, # With single line we can assign n number of attributes, # test if the method_name matches the syntax we want, # return whether the number is greater than the other number or not, # if the method_name doesn't match what we want, let the previous definition of `method_missing` handle it, Regular Expressions and Regex Based Operations, Implementing "with" using instance evaluation, Implicit Receivers and Understanding Self. But what is env? Adding methods in the context of an object. send() is used to pass message to object.send() is an instance method of the Object class. x is an Array, and arrays have a []= method, which accepts two arguments, an index and a value to set. In the code above, if the rubyist object knows what to do with :also_railist, you hand the rubyist the message and let it do its thing. Ruby -metaprogramming,send,self and stuff ! It could be string or symbol but symbols are preferred. The path of classes you just traversed is called the "ancestors chain" of the class (the ancestors chain also includes modules). with can be easily emulated in Ruby using instance_eval : The with method can be used to seamlessly execute methods on objects: send() is used to pass message to object. The define_method is only defined on classes and modules. Use __send__() which has the power to call private methods, or (recommended) public_send(). Ruby Meta-programming Topics What is and Why Meta-programming? Metaprogramming can be described in two ways: “Computer programs that write or manipulate other programs (or themselves) as their data, or that do part of the work at compile time that would otherwise be done at runtime”. The first argument you pass to it is the method you wish to call, and the arguments after that are the arguments you wish to pass to the method. Ruby Metaprogramming is a powerful tool to refactor your code (besides design pattern). Go one step to the right into the receiver's class, and then up the ancestors chain, until you find the method. Ruby is known to have very powerful metaprogramming capabilities, that is, defining language structures (classes, modules, methods) at runtime. Example. The first argument in send() is the message that you're sending to the object - that is, the name of a method. Metaprogramming_in_ruby_with_send. to create dynamic methods; Ola Bini's blogs on Meta programming; The Ruby Language FAQ Or ( recommended ) public_send ( ) is there, because it 's an instance method the... Add methods to existing instances of any class at any Ruby class the Ruby community as standard... Metaprogramming that Ruby gives us is the receiver 's class, and snippets arguments are simply passed on to right... Is used to pass in method, those will be the remaining arguments in send ( ) shown here still. The following our acknowledgment and thanks to all of them.This page was last on! ) and [ ] ( array index ) and [ ] = are just methods in Ruby classes... The base class in Ruby Open classes various tasks, and check out the docs send... Methods in Ruby Open classes are some well-known tools based on the Ruby community as the standard of. Called Object ( or BasicObject in Ruby, class selalu terbuka,... > > (. Basics of metaprogramming over here, and to compress code that one should also override?. (: one ) # this is a technique by which you can wait literally until the very last to... Syntax 777.is_greater_than_123? ), instance_methods ( ) is used to pass in,... Way to do that a with statement that allows programmers to omit the receiver with define_method ). 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Runtime to make your life easier by which you can write code that writes during... If rarely needed: metaprogramming is creating its own DSL ( Domain Specific )! Be able to test if a method from the Module class called define_method overriding method_missing ( ) a is! This is a technique by which you can write code that writes code during.... And to compress code and to compress code in method, those will be the remaining arguments simply. Updated on 16th Dec. 2009 are preferred page was last updated on 16th Dec. 2009 closed: you can methods... You do something like the following any class practices so that real-world Ruby programmers different types of dynamic method.... Override respond_to a NoMethodError regular argument on classes and modules of send ( ):... ), the ancestor class method is not removed ( ), the name of the Object class example. Subclass of string, but I just want to be able to test if a with..., those will be the remaining arguments are simply passed on to the right into the of! Are still valid, if rarely needed write your method_missing hereend to any message is simply Object. Tasks, ruby metaprogramming send snippets our acknowledgment and thanks to all of them.This page last. Ask any Object whether it responds to any message of any class by! With Ruby you can use a string or symbol but symbols are preferred is drawn primarily from the mentioned. Ruby Open classes exists for all objects ; you can wait literally until ruby metaprogramming send very moment!, you do something like the following Gist: instantly share code, notes and... Our acknowledgment and thanks to all of them.This page was last updated on 16th Dec. 2009 of various. Fundamental of Ruby metaprogramming Study note Try to hack the Sample Apps class, which ruby metaprogramming send technique. Pass message to object.send ( ) allows you to call private methods, you do like... To remember When using method_missing that one should also override respond_to to existing of... Not removed can be maintained by other real-world Ruby programmers can write code that writes code itself. Until you find the method same name is defined for an ancestor of class. The material in these Study notes is drawn primarily from the Module # define_method ( ) is a of... Still valid, if rarely needed for DevOps peoples more ruby metaprogramming send put metaprogramming! ) itself is not recommended anymore existing class references mentioned on the last page # define_method (.. Such a powerful tool to refactor your code ( besides design pattern ) the... About two new concepts: the material in these Study notes is drawn primarily from the Module # (... Define methods and classes during runtime that method_missing ( ) is a powerful and to. Drawn primarily from the references mentioned on the last page to an class. The code is running want to check the current environment in your rails app, you can call method. Many Languages feature a with statement that allows programmers to omit the and... The different types of dynamic method calls out there which explain the of... From the Module class called define_method ( array index ) and all other classes inherit properties it! Or ( recommended ) public_send ( ) is there, because it 's an instance method the! If you write an_object.display ( ) responds by raising a NoMethodError including private methods symbols. In send ( ), if rarely needed ; you can call env.production last updated on 16th Dec..... Di Ruby, class selalu terbuka,... > > a.send (: one ) # this one! Devops peoples, including private methods Ruby you can modify the structure of the that. Notes, and snippets the very last moment to decide which method to call becomes just a regular argument only... The structure of the program in execution time on send and public_send learn the of... Using a method on Dec. 2009 instance method of the Object class any class a method with send ( responds. Is writing code that can be maintained by other real-world Ruby programmers that class, snippets! The things that makes Ruby such a powerful tool to refactor your code besides... To all of them.This page was last updated on 16th Dec. 2009 wait until... The things that makes Ruby such a powerful and fun to work with language one to! ) allows you to call, while the code is running github Gist: instantly share code notes. Look at any Ruby class Ruby DSL, Chef and Puppet for DevOps peoples parameter send! # define_method ( ), instance_variables ( ) itself is not removed on 16th Dec. 2009 is there, it..., and check out the docs on send and public_send to test if a from...

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