Ruby variable

Ruby global variable

Global variables to $ the beginning. The value of an uninitialized global variable is nil , in use of -w option, a warning is generated.

Assigning values to global variables changes the global state, so it is not recommended to use global variables.

The following example shows the use of global variables.

#!/usr/bin/ruby#-*- coding: UTF-8
-*-$global_variable=10classClass1defprint_globalputs"Global variables output in Class1 as
#$global_variable"endendclassClass2defprint_globalputs"Global variables output in Class2 as
#$global_variable"endendclass1obj=Class1.newclass1obj.print_globalclass2obj=Class2.newclass2obj.print_global

Global variables output in Class1 as 10
Global variables output in Class2 as 10

Ruby instance variable

Instance variable to @ the beginning. The value of an uninitialized instance variable is nil , in use of -w option, a warning is generated.

The following example shows the use of instance variables.

#!/usr/bin/rubyclassCustomerdefinitialize(id,name,addr)@cust_id=id@cust_name=name@cust_addr=addrenddefdisplay_details()puts"Customer
id #@cust_id"puts"Customer name #@cust_name"puts"Customer address
#@cust_addr"endend#create objectcust1=Customer.new("1","John","Wisdom
Apartments, Ludhiya")cust2=Customer.new("2","Poul","New Empire road,
Khandala")#calling methodcust1.display_details()cust2.display_details()

Customer id 1
Customer name John
Customer address Wisdom Apartments, Ludhiya
Customer id 2
Customer name Poul
Customer address New Empire road, Khandala

Ruby class variable

Class variables to @@ at the beginning and must be initialized before it can be used in the method definition.

Referencing an uninitialized class variable results in an error. A class variable can be shared among subclasses or submodules of the class or modulein which it is defined.

In use -w option, overloading the class variable generates a warning.

The following example shows the use of class variables.

#!/usr/bin/rubyclassCustomer@@no_of_customers=0definitialize(id,name,addr)@cust_id=id@cust_name=name@cust_addr=addrenddefdisplay_details()puts"Customer
id #@cust_id"puts"Customer name #@cust_name"puts"Customer address
#@cust_addr"enddeftotal_no_of_customers()@@no_of_customers+=1puts"Total
number of customers:
#@@no_of_customers"endend#create objectcust1=Customer.new("1","John","Wisdom
Apartments, Ludhiya")cust2=Customer.new("2","Poul","New Empire road,
Khandala")#calling methodcust1.total_no_of_customers()cust2.total_no_of_customers()

Total number of customers: 1
Total number of customers: 2

Ruby local variable

Local variables are lowercase or underlined \_ the beginning. The scope of local variables ranges from class 、 module 、 def or do to the corresponding end or from the left brace to the right brace {} .

When an uninitialized local variable is called, it is interpreted as callinga method without parameters.

Assigning values to uninitialized local variables can also be treated as variable declarations. The variable will exist until the end of the current domain. The life cycle of a local variable is determined when the Ruby parser is used.

In the above example, the local variable is id 、 name and addr .

Ruby constant

Constants begin with uppercase letters. Constants defined within a class or module can be accessed from within the class or module, and constants defined outside the class or module can be accessed globally.

Constants cannot be defined in a method. Referencing an uninitialized constant results in an error. A warning is generated for a constant assignment that has been initialized.

#!/usr/bin/ruby#-*- coding: UTF-8
-*-classExampleVAR1=100VAR2=200defshowputs"The value of the first constant is
#{VAR1}"puts"The value of the second constant is
#{VAR2}"endend#create objectobject=Example.new()object.show

The value of the first constant is 100
The value of the second constant is 200

Ruby pseudo variable

They are special variables that look like local variables, but behave like constants. You cannot assign any values to these variables.

• self :The sink object for the current method

• true :Representative true value.

• false :Representative false value.

• nil :Representative undefined value.

• \__FILE__ :The name of the current source file.

• \__LINE__ :The number of the current line in the source file.