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Metaprogramming in Ruby
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- 4. What? Writing code thatwrites code Writing code that manipulates language constructs at runtime
- 5. • write ownDSL • remove duplications in the code • enhance basic Ruby Why?
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- 7. Class is anobject, Object is a class class is a keyword, class is a method method is a method, Method is a class Object Model
- 8. Class is anObject
- 9. Module is anObject
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- 13. Singleton Method/Class class Asingleton class
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- 18. Open class NOT Objects •comments (# comment, =begin =end) • punctuation marks (, ; ( .) • statements (if while for defined? yield super) • operators (&. || && =) • blocks (do..end, {..}) • methods (not method objects) Methods are a fundamental part of Ruby's syntax, but they are not values that Ruby programs can operate on. That is, Ruby's methods are not objects in the way that strings, numbers, and arrays are. It is possible, however, to obtain a Method object that represents a given method, and we can invoke methods indirectly through Method objects. (c) The Ruby Programming Language. D. Flanagan; Y. Matsumoto operators table
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- 23. Test: Ruby orRails? ActiveSupport 3 Ways to Monkey-Patch
- 24. why is nobodyusing refinements Refinements • Applicable only for classes • Works in the current lexical scope (module/class definition, EOF)
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- 31. respond_to? Rules: • Redefine respond_to_missing?(name) •Call super respond_to? vs respond_to_missing?
- 32. Dynamic vs Ghost useDynamic Methods if you can use Ghost Methods if you have to
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- 34. Alias Method alias vsalias_method
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- 36. Block Reccomendation: 1 line- curly braces, multiple lines - do..end
- 37. & operator yield isnot enough: • pass block to another method • convert block to Proc
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- 39. LambdaProc returns fom thescope where it is defined returns from itself checks the aritydoes not check the arity
- 40. Lambdas vs Methods lambdais evaluated in the scope it is defined, method is evaluated in the scope of object
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- 43. *eval methods *eval vs*exec methods
- 44. def current_user def user_signed_in? defauthenticate_user! def user_session
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- 46. Statements / Methods •BasicObject#__send__ • BasicObject#method_missing • Kernel#send • Kernel#public_send • Kernel#method • Kernel#class • Kernel#define_singleton_method • Kernel#block_given? • Kernel#respond_to_missing? • Kernel#respond_to? • Kernel#eval • yield • defined? • alias • super • class • module • def • Module#module_eval • Module#define_method • Module#alias_method • Module#included • Module#refine • Module#using
- 47. Summary • Avoid metaprogrammingif it is possible! • Be smart in monkeypatching • Statements are not methods • Prefer lambdas over procs • Use super in method_missing • Keep scope in mind • Comment out!
- 48. 1. Metaprogramming Ruby2.0 (book) 2. The Ruby Programming Language (book, Reflection and Metaprogramming section) 3. Ruby Under a Microscope (Objects and Classes, Constants Lookup) 4. Codebases lessons Investigate Further