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+# Default Directory Structure
+```
+rails_root  
+|-- app  
+|   |-- assets  
+|   |-- controllers  
+|   |   `-- application.rb  
+|   |-- helpers  
+|   |   `-- application_helper.rb  
+|   |-- models  
+|   `-- views  
+|       `-- layouts  
+|-- components  
+|-- config  
+|   |-- enviroments  
+|   |   |-- development.rb  
+|   |   |-- production.rb  
+|   |   `-- test.rb  
+|   |-- database.yml  
+|   |-- enviroment.rb  
+|   `-- routes.rb  
+|-- db  
+|-- doc  
+|-- lib  
+|-- log  
+|   |-- development.log  
+|   |-- production.log  
+|   |-- server.log  
+|   `-- test.log  
+|-- public  
+|-- script  
+|-- test  
+|   |-- fixtures  
+|   |-- functional  
+|   |-- mocks  
+|   |-- unit  
+|   `-- test_helper.rb  
+`-- vendor  
+```
+# Methods
+### Strings
+capitalize!  
+center  
+chomp!  
+chop  
+concat  
+count  
+crypt  
+delete!  
+downcase!  
+dump  
+each  
+each_byte  
+empty?  
+gsub!  
+hash  
+hex  
+include?  
+index  
+intern  
+length  
+|just, rjust  
+next!  
+oct  
+replace  
+reverse!  
+rindex  
+scan  
+slice!  
+split  
+squeeze!  
+strip!  
+sub!  
+sum  
+swapcase!  
+tr!  
+tr_s  
+unpack  
+upcase!  
+upto  
+
+### Regex
+escape  
+last_match  
+new  
+quote  
+casefold?  
+kcode  
+match  
+source  
+### Time
+asctime    
+ctime  
+day  
+gmt?  
+gmtime  
+hour  
+isdst  
+localtime  
+mday  
+min  
+mon  
+month  
+sec  
+strftime  
+tv_sec  
+tv_usec  
+usec  
+utc  
+utc?  
+wday  
+yday  
+year  
+zone  
+### Arrays
+assoc  
+at  
+clear  
+collect!  
+compact!  
+concat  
+delete  
+delete_at  
+delete_if  
+each  
+each_index  
+empty?  
+eql?  
+fill  
+first  
+flatten!  
+include?  
+index  
+indexes  
+join  
+last  
+length  
+nitems  
+pack  
+pop  
+push  
+rassoc  
+reject!  
+replace  
+reverse!  
+reverse_each  
+rindex  
+shift  
+slice!  
+sort!  
+uniq!  
+unshift  
+
+### Validation
+condition_block?  
+create!  
+evaluate_condition  
+validate  
+validate_on_create  
+validate_on_update  
+validates_acceptance_of  
+validates_associated  
+validates_confirmation_of  
+validates_each  
+validates_exclusion_of  
+validates_format_of  
+validates_inclusion_of  
+validates_length_of  
+validates_numericality_of  
+validates_presence_of  
+validates_size_of  
+validates_uniqueness_of  
+
+### Enumerable Mixin
+collect  
+each_with_index  
+entries  
+find  
+find_all  
+grep  
+include?  
+max  
+min  
+reject  
+sort  
+
+# Pre-defined Variables
+$! Exception information  
+$& String of last match  
+$` String left of last match  
+$' String right of last match  
+$+ Last group of last match  
+$N Nth group of last match  
+$= Case insensitive flag  
+$/ Input record separator  
+$\ Output record separator  
+$, Output field separator  
+$. Current line number of last file read  
+$> Default output for print  
+$_ Last input line of string  
+$0 Name of script  
+$* Command line arguments  
+$stderr Standard error output  
+$stdin Standart input  
+$stdout Standart output  
+$-a True if -a is set.  
+$-d Status of -d switch  
+$-l True if -l is set  
+$-p True if -p is set  
+$-v Verbose Flag  
+
+# Reserved Words
+begin  
+elsif  
+rescue  
+=end  
+end   
+retry  
+BEGIN  
+ensure  
+return  
+END  
+false  
+self  
+alias  
+for  
+super  
+and  
+if  
+then  
+begin  
+in  
+true  
+break  
+module  
+undef  
+case  
+next  
+unless  
+class  
+nil  
+until  
+def  
+not  
+when  
+defined?  
+or  
+while  
+do  
+redo  
+yield  
+else  
+
+# Regular Expression Syntax
+
+`^` Start of string  
+`$` End of string  
+`.` Any single character  
+`(a|b)` a or b  
+`(...)` Group section  
+`[abc]` Item in range (a or b or c)  
+`[^abc]` Not in range (not a or b or c)  
+`a?` Zero or one of a  
+`a*` Zero or more of a  
+`a+` One or more of a  
+`a{3}` Exactly 3 of a  
+`a{3,}` 3 or more of a  
+`a{3,6}` Between 3 and 6 of a  
+`!(pattern)` "Not" prefix. Apply rule when URL does not match pattern.