Ruby01: Beginner
中整個早上都忙著作業,看來是假期懶了一下現在現眼報吧哈哈。在上課之前發一下Ruby 的首章,算是倉促的開始吧。
puts
puts "Once upon a time...
there's a self learn programmer...." #okay
puts
"Once upon a time...
there's a self learn programmer...." # output: *blank*
所以Ruby 是case-sensitive 咯?但在網上卻是這樣說:“Whitespace characters such as spaces and tabs are generally ignored in Ruby code, except when they appear in strings. ”(Tutorial Point)。所以,我們推斷 Ruby command 是不可以被分開的。
puts vs print
puts "Hello World" #auto-append "\n" print "I am in " #not appending "\n" print "campus"
output:
Hello World
I am in campus
啊,要去上課了,待續...
https://www.tutorialspoint.com/ruby/ruby_comments.htm
BEGIN{} & END{} Priorities
puts "in the middle, even written in front?! " BEGIN{ puts "prog initialize" } END{ puts "just before prog termination" }
output:
prog initialize
in the middle, even written in front?!
just before prog termination
Block commenting
=begin
block comment
instead of using #
=end
Class in Ruby
#in Ruby, everything treated as object
#in Ruby, everything treated as object $ monthly_customers = 0; class Customer @@no_of_customers = 0; #class var: static DM: all obj share 1 copy #member function in ruby class def initialize(id, name, addr) #initialize: the reserved method for constructors #lowercase letters for method name @cust_id = id #instance var == DM @cust_name = name @cust_addr = addr end def modify_addr(addr2) ::Customer.instance_variable_get(:@cust_addr) = addr2 #modify instance var in same class end end cust1 = Customer.new(", "Amy", "CauswayBay, HK") cust2 = Customer.new; p cust2.instance_variable_get(:@cust_id) #nil: access uninitialized instance variable cust2.initialize(", "Timonthy", "Kwai Shing") p cust2.instance_variable_get(:@cust_id) # "02"
差不多要上課了,待續...
https://www.tutorialspoint.com/ruby/ruby_variables.htm
https://www.tutorialspoint.com/ruby/ruby_class_case_study.htm
Global variable in Ruby
$global_variable = "Hello kitty" #define a global var class Class1 def print puts "Global variable is: #$global_variable" #access global var end end #to finish class definition class1obj = Class1.new class1obj.print #no global fnc in ruby: fnc involved by obj only
Local variable, constant & execution order
$global_variable = "Hello kitty" #define a global var class Class1 @@object_Counter = 1 #no space btw '@@' and identifier name FIXED_VALUE = 100 #const var starts with capital, local var starts with lower case def print @local_var = "Hello global" puts "Global variable is: #$global_variable" #access global var puts "Instance varable ~ DM: #@local_var" #access instance var puts "Existing objects = #@@object_Counter" end puts "when local variable out of scope: #@local_var" # codes defined out of any class method executed first: ~ global MF puts "The constant in class : #{FIXED_VALUE}" #access constant end #to finish class definition class1obj = Class1.new class1obj.print #no global fnc in ruby: fnc involved by obj only
output:
when local variable out of scope: The constant in class : 100 Global variable is: Hello kitty Instance varable ~ DM: Hello global Existing objects = 1 => nil
to be continued...
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