The send Method in Ruby

1. Call a Method Without the send Method in Ruby
2. Use the send Method to Invoke Private Method in Ruby
3. Use the send Method to Invoke Method at Runtime in Ruby

In Ruby, there are several ways to call a method. This article will discuss the use of the send method and its benefits.

Call a Method Without the send Method in Ruby

Usually, we would use . followed by the method name to call a method on an object.

Consider the following example:

[1, 2, 3].join
=> "123"

The method join is called on the array [1, 2, 3] in the code snippet above. Using . only works on the object’s public methods; calling a private method is impossible.

Use the send Method to Invoke Private Method in Ruby

To call a private method, use the send method. Consider the following code snippet.

class Foo
  private

  def secret
    'secret that should not be told'
  end

  def my_asset(amount, location)
    "I have #{amount}$ in #{location}"
  end
end

Foo.new.secret
Foo.new.my_asset(100, 'the basement')

Output:

NoMethodError: private method 'secret' called for #<Foo>
NoMethodError: private method 'my_asset' called for #<Foo>

We must use the send method to call the methods defined under the private keyword.

Foo.new.send(:secret)
Foo.new.send(:my_asset, 100, 'the basement')

Output:

=> "secret that should not be told"
=> "I have 100$ in bank"

The send method’s first argument is the method name, which can be a string or a symbol. The origin method’s arguments are also accepted via the second and third arguments, and so on.

Use the send Method to Invoke Method at Runtime in Ruby

When there is a variable that stores the method name, send comes in handy.

Example:

class Report
  def format_xml
    'XML'
  end

  def format_plain_text
    'PLAIN TEXT'
  end
end

def get_report_format(extension)
  if extension == 'xml'
    'format_xml'
  else
    'format_plain_text'
  end
end

report_format = get_report_format('xml')
report = Report.new
formated_report = report.send(report_format)

Output:

"XML"

The class Report is responsible for generating the format in the example above. It supports format_xml and format_plain_text.

We also have a method called get report_format, which returns the format that Report supports.

We can’t use the . notation to call format_xml directly. Instead, we must use the send function: report.send(report format).