Generating GUIDs in Ruby for SketchUp API Integration: A Practical Guide

When working with the SketchUp API, you might encounter situations where you need to generate a Globally Unique Identifier (GUID). This is often necessary for identifying specific entities, tracking changes, or interfacing with external services. While uniqueness is ideal for GUIDs, sometimes you might only need a pseudo-unique identifier for internal use.

This article explores different methods for generating GUIDs in Ruby, focusing on efficiency and practicality for SketchUp API integration.

The Challenge: SecureRandom and Performance

The Ruby standard library provides the SecureRandom module, which is a common choice for generating UUIDs (Universally Unique Identifiers, a type of GUID). Here's how you would typically use it:

require 'securerandom'

t = Time.now
uuid = SecureRandom.uuid
puts "#{Time.now - t} seconds to generate guid."
puts uuid

However, as pointed out in the SketchUp forum discussion, SecureRandom can be surprisingly slow on its first use within a SketchUp environment. The initial call might freeze SketchUp for an extended period (observed as 24 seconds in the forum thread), though subsequent calls are much faster.

This performance hit can be problematic, especially within a responsive SketchUp tool. Let's explore alternative solutions.

Alternatives for Faster GUID Generation

If true uniqueness isn't critical and you only need to generate a small number of identifiers, several faster approaches can be used.

1. Time-Based Pseudo-GUID

One simple method combines the current time with some random data. While this doesn't guarantee uniqueness across different systems or over long periods, it's often sufficient for internal use within a single SketchUp session.

def generate_pseudo_guid
  Time.now.to_f.to_s.gsub('.', '') + rand(10000).to_s # Combine timestamp with random number
end

guid = generate_pseudo_guid
puts guid

Explanation:

• Time.now.to_f: Gets the current time as a floating-point number (seconds since the epoch including fractional seconds).
• to_s: Converts the number to a string.
• gsub('.', ''): Removes the decimal point to create a longer, seemingly random string.
• rand(10000).to_s: Appends a random four-digit number to further increase uniqueness.

2. Simple Random Number Generation

If you just need a unique-ish identifier for the current SketchUp session, simple random number generation could be sufficient.

def generate_simple_id
  rand(1000000) # Generate a random number up to 1 million
end

id = generate_simple_id
puts id

Caution: This method offers the lowest guarantee of uniqueness and should only be used when collisions are highly unlikely and acceptable.

3. Leveraging Ruby's rand with Formatting

You can create a GUID-like string by formatting random numbers with the format that GUIDs typically possess.

def generate_formatted_random_guid
  "%08x-%04x-%04x-%04x-%12x" % [rand(0x100000000), rand(0x10000), rand(0x10000), rand(0x10000), rand(0x1000000000000)]
end

guid = generate_formatted_random_guid
puts guid

Hash for Uniqueness Verification

Regardless of the method you choose, it's good practice to use a hash or set to verify uniqueness, especially when generating multiple identifiers.

generated_guids = Set.new # Requires 'set'

def generate_unique_guid(existing_guids)
  guid = generate_pseudo_guid # Or use any of the above methods
  while existing_guids.include?(guid)
    guid = generate_pseudo_guid
  end
  existing_guids.add(guid)
  guid
end

#example usage:
new_guid = generate_unique_guid(generated_guids)
puts new_guid

Explanation:

• A Set is used to store already generated GUIDs efficiently. You'll need to require 'set' to use this.
• The generate_unique_guid function continues generating GUIDs until it finds one not already in the set.

Choosing the Right Approach

The best method for generating GUIDs in your SketchUp API script depends on your specific requirements:

• High Uniqueness Required: If true uniqueness is essential, consider using SecureRandom.uuid and accept the initial performance hit. You may pre-generate some UUIDS on Sketchup startup in order to avoid the wait when the user clicks a specific button.
• Moderate Uniqueness, Fast Generation: A time-based or formatted random number approach provides a good balance for internal use.
• Simple Identification, Minimal Collisions: Basic random number generation can be sufficient for temporary identification within a session.

Always consider the potential for collisions and implement a verification mechanism if uniqueness is important to your application. Use tools like the Ruby Set class to quickly verify if a new GUID has been generated already.

By understanding the trade-offs between performance and uniqueness, you can choose the most effective GUID generation strategy for your SketchUp API projects.