Table of Contents
What is main difference between variable and constant?
A constant does not change its value and it remains the same forever. A variable, on the other hand, changes its value from time to time depending on the equation. Constants are usually represented by numbers. Variables are usually represented by alphabets.
What are constants in Ruby?
A constant in Ruby is like a variable, except that its value is supposed to remain constant for the duration of a program. Although constants look like local variables with capital letters, they have the visibility of global variables: they can be used anywhere in a Ruby program without regard to scope.
What are class variables in Ruby?
Used declare variables within a class. There are two main types: class variables, which have the same value across all class instances (i.e. static variables), and instance variables, which have different values for each object instance.
How do I use a class variable in Ruby?
Ruby Class Variables Class variables begin with @@ and must be initialized before they can be used in method definitions. Referencing an uninitialized class variable produces an error. Class variables are shared among descendants of the class or module in which the class variables are defined.
What are Ruby symbols?
Ruby uses symbols, and maintains a Symbol Table to hold them. Symbols are names – names of instance variables, names of methods, names of classes. So if there is a method called control_movie, there is automatically a symbol :control_movie. Ruby’s interpreted, so it keeps its Symbol Table handy at all times.
What data types does Ruby use?
There are different data types in Ruby as follows:
- Numbers.
- Boolean.
- Strings.
- Hashes.
- Arrays.
- Symbols.
How do you check the type of a variable in Ruby?
The proper way to determine the “type” of an object, which is a wobbly term in the Ruby world, is to call object. class . Since classes can inherit from other classes, if you want to determine if an object is “of a particular type” you might call object.
How do you create a local variable in Ruby?
Local Variables: A local variable name always starts with a lowercase letter(a-z) or underscore (_). These variables are local to the code construct in which they are declared. A local variable is only accessible within the block of its initialization. Local variables are not available outside the method.
How to access the value of a constant in Ruby?
NOTE − In Ruby, you CAN access value of any variable or constant by putting a hash (#) character just before that variable or constant. Instance variables begin with @. Uninitialized instance variables have the value nil and produce warnings with the -w option. Here is an example showing the usage of Instance Variables.
How many types of variables are there in Ruby?
There are five types of variables supported by Ruby. You already have gone through a small description of these variables in the previous chapter as well. These five types of variables are explained in this chapter. Global variables begin with $. Uninitialized global variables have the value nil and produce warnings with the -w option.
How to create an instance variable in Ruby?
The instance variable name must start with ‘@’ character, otherwise instance variable names follow the rules as a local variable (discussed earlier) name. In the following example, Student.new creates a new object – an instance of the class Student. The instance variables @student_id and @student_name.
Do you have to initialize class variables in Ruby?
Class variables begin with @@ and must be initialized before they can be used in method definitions. Referencing an uninitialized class variable produces an error. Class variables are shared among descendants of the class or module in which the class variables are defined.