Ruby

Mastering `Ruby` Method Names: A Guide to Variable Assignment

When working with Ruby, accurately naming and managing method names is crucial, especially when you encounter situations that challenge conventional patterns. One intriguing conundrum arises when trying to set variables using method calls that resemble those in ActiveRecord objects. The problem intensifies when you discover that some of your desired variable names contain periods, which complicate your syntax. This post outlines the problem, provides a cautionary approach, and offers an unconventional yet effective solution for your Ruby projects.

The Problem

In a recent Ruby project, a developer aimed to override the method_missing method to enable a dynamic way to assign variable values using a syntax similar to:

Object.variable_name = 'new value'

However, the situation becomes more complex when variable names include periods. For example, the developer discovered they could work around this issue by using:

Object.send('variable.name=', 'new value')

Although this method works, the desire remains to use the more readable and elegant syntax of:

Object.variable.name = 'new value'

The Caution: Don’t Do It!

Before diving into a workaround, it’s vital to emphasize one crucial point: Don’t create identifiers in Ruby that are not valid! Trying to circumvent the language’s conventions can lead to unreliable code and confusion. If you want to use this approach for clarity, consider leveraging Ruby’s built-in attr_writer, attr_reader, and attr_accessor, which are designed explicitly for this purpose. For instance:

attr_writer :bar
attr_reader :baz
attr_accessor :foo

The Solution: A Creative Approach with `method_missing`

Despite the caution, if you are still eager to pursue this path, here’s how you can achieve it using a custom class and the method_missing method. The key here is to return another instance of the same class whenever you access a method, allowing you to collect the necessary information as you navigate through your method calls.

Implementation

Here’s a practical implementation of this concept with the class SillySetter:

class SillySetter
  def initialize(path = nil)
    @path = path
  end

  def method_missing(name, value = nil)
    new_path = @path ? "#{@path}.#{name}" : name
    if name.to_s[-1] == ?=
      puts "setting #{new_path} #{value}"
    else
      return self.class.new(path = new_path)
    end
  end
end

s = SillySetter.new
s.foo = 5              # -&gt; setting foo= 5
s.foo.bar.baz = 4      # -&gt; setting foo.bar.baz= 4

Explanation

Initialize Method: The constructor initializes the path variable that keeps track of the method names as they are chained.
method_missing: This method intercepts calls to methods that aren’t explicitly defined.
- If a method is called that ends with an equal sign (=), it recognizes this as a setter and outputs the new value being set.
- If the method doesn’t conclude with =, it creates a new instance of SillySetter with the updated path.

Conclusion

In Ruby, while it’s tempting to take the complex route of creating identifiers with periods in their names, it’s a practice that can lead to confusion and complications in your code. However, should you decide to proceed with such unconventional approaches, implementing the method_missing method as shown can afford you the flexibility to set variable names dynamically, though with a hefty warning attached!

Master your method names wisely, and happy coding!

Mastering Ruby Method Names: A Guide to Variable Assignment