Ruby – Method Invocation

Method invocation refers to how a method is called in a program. The process of invoking a method in Ruby is quite easy since the use of parenthesis is optional. The use of parenthesis plays an important role when the invocation is embedded inside an expression consisting of other function calls or operators.

The Ruby interpreter makes use of the process known as method lookup or method resolution. In this method, when the Ruby interpreter has the method’s name and the object on which it is to be invoked, it searches for the method definition.

A Method Invocation Expression Comprises of 4 Components:

• The expression whose value is the object on which the method is call. Now, this expression is followed by either . or :: which is used to separate expression from the method name. This separator and expression is optional. If the separator and expression are absent, then method is invoked on the ‘self’.
• The name of the method being call.
• The parameter values is passed to the method. The list of comma-separated arguments can be passed to the method enclosed within parenthesis if the method contain more than one argument. These arguments are optional.
• An optional block of code enclosed in curly braces or by a ‘do/end’ pair. This code can be invoked this block of code with the help of the ‘yield’ keyword.

Example 1: In this example, we invoke a method with no arguments.

# Ruby program to illustrate
# how to invoke a method
example_str ='GeeksforGeeks'

# "length" invoked on object
# example_str having no args
puts example_str.length

Output:

13

Example 2: In this example, we invoke a method with one argument.

# Ruby program to illustrate
# how to invoke a method

# "sqrt" invoked on object
# Math with one argument
number = Math.sqrt(36)
puts "Square Root of 36:"
puts number

Output:

Square Root of 36:
6.0

Example 3: In this example, we’re going to define a method with two arguments. Then we will call this method.

# Ruby program to illustrate
# how to invoke a method
def add(a, b)

# ’add’ method definition
  a + b
end

# Calling method ‘add’
c = add(20, 30)
d = add(45, 90)
puts c
puts d

Output:

50
135

Example 4: In this example, we are going to invoke class methods.

# Ruby program to illustrate
# how to invoke a method

# ’Animal’ class definition
class Animal

   # ’dog’ function definition
   # having no arguments
   def dog
       puts "Dog is barking"
   end

   # ’enternames’ function definition
   # having two arguments
   def  enternames(one, two)
           puts one
           puts two
   end
end

# Create a new instance of Animal
animal = Animal.new

# Instance method invocation
animal.dog

# Instance method invocation
# having two arguments
animal.enternames("Cat", "Elephant")

# Class method call using send method
animal.send :dog

# Class method call using send method
animal.send :enternames, "Cat", "Elephant"

Output:

Dog is barking
Cat
Elephant
Dog is barking
Cat
Elephant