This library makes your YAML configuration files available via a nice API. It also supports different configurations for each RAILS_ENV environment and using plugins to return more complex settings values. 🚀

ComplexConfig follows a well-defined architectural pattern with clear separation of concerns between several key components:

Provider (ComplexConfig::Provider)

• The central hub managing configuration loading, caching, and access 🔄
• Handles environment-specific configuration selection 🌍
• Manages plugin registration and execution 🔌
• Provides memoization for performance optimization ⚡

Settings (ComplexConfig::Settings)

• Represents structured configuration data with nested access 📊
• Implements dynamic attribute access through method_missing 🧠
• Supports conversion between different representations (hash, YAML, JSON) 🔄
• Provides deep freezing for immutability 🔒

Proxy (ComplexConfig::Proxy)

• Enables lazy evaluation of configuration access ⏳
• Defers loading until first method call 🚦
• Supports environment-specific lookups 🌐
• Handles safe existence checking ❓

graph LR
    A[Provider] --> B[Settings]
    A --> C[Proxy]
    B --> D[Configuration Files]
    C --> B
    A --> E[Plugins]
    E --> B

The Provider acts as the main coordinator, loading configuration files and creating Settings objects. The Proxy enables lazy loading, while Plugins can augment or transform attribute values at runtime.

ComplexConfig supports two primary access patterns if required via require "complex_config/rude":

1. Environment-aware access via cc.config_name (uses RAILS_ENV by default): 🌐

   # Loads config/products.yml and applies environment-specific settings
   cc.products

2. Explicit environment access via complex_config.config_name (skips automatic environment namespace): 🧪

   # Loads config/products.yml without environment prefix
   complex_config.products

The proxy system automatically resolves configuration file paths based on method names, mapping cc.products to config/products.yml.

When using the default cc accessor, ComplexConfig automatically applies environment-specific configurations. For example, with a YAML file like:

development:
  database:
    host: localhost
    port: 5432
production:
  database:
    host: db.production.example.com
    port: 5432

Accessing cc.database.host will return "localhost" in development and "db.production.example.com" in production, automatically selecting the appropriate environment section.

ComplexConfig integrates seamlessly with Rails application lifecycle. During development, when Rails reloads classes (or the user types reload! into the console), ComplexConfig automatically flushes its internal cache to ensure that configuration changes are picked up correctly. This behavior is handled through the Railtie integration which hooks into Rails' to_prepare callback.

ComplexConfig employs memoization through the mize gem to cache expensive operations like file loading and parsing. In production environments, this caching provides performance benefits, while in development, Rails' reloading mechanism ensures configuration changes are respected.

• Delegation: Provider delegates to Settings for attribute access 🔄
• Strategy Pattern: Plugins provide different strategies for attribute resolution 🧠
• Lazy Loading: Proxy defers configuration loading until needed ⏳
• Singleton: Provider follows singleton pattern for consistent configuration access 🔁

This architecture enables flexible, performant configuration management while maintaining clean separation between concerns.

You can use rubygems to fetch the gem and install it for you:

gem install complex_config

You can also put this line into your Gemfile

gem 'complex_config', require: 'complex_config/rude'

and bundle. This command will enable all the default plugins and make the cc and complex_config shortcuts available. The configurations are expected to be in the config subdirectory according to the rails convention.

Given a config file like this and named config/products.yml

development:
  flux_capacitor:
    version_20:
      name: Flux Capacitor Version 2.0
      price_in_cents: 12_000_00
      manual_pdf_url: "http://brown-inc.com/manuals/fc_20.pdf"
      components:
        - Miniature Chrono-Levitation Chamber (mCLC)
        - Single Gravitational Displacement Coil (SGDC)
        - Simple Quantum Flux Transducer (SQFT)
        - Basic Time-Space Navigation System (BTN)
    pro_version:
      name: Flux Capacitor Professional
      price_in_cents: 23_000_00
      manual_pdf_url: "http://brown-inc.com/manuals/fc_pro.pdf"
      components:
        - Advanced Chrono-Levitation Chamber (ACL)
        - Dual Gravitational Displacement Coils (DGDCs)
        - Advanced Quantum Flux Transducer (AQFT)
        - Professional Time-Space Navigation System (PTNS)
    enterprise_version:
      name: Flux Capacitor Enterpise
      price_in_cents: 1_600_000_00
      manual_pdf_url: "http://brown-inc.com/manuals/fc_enterprise.pdf"
      components:
        - Super-Advanced Chrono-Levitation Chamber (SACL)
        - Quadruple Gravitational Displacement Coils (QGDCs)
        - Ultra-Advanced Quantum Flux Transducer (UAQFT)
        - Enterprise Time-Space Navigation System (ETNS)
test:
  flux_capacitor:
    test_version:
      name: Yadayada
      price_in_cents: 6_66
      manual_pdf_url: "http://staging.brown-inc.com/manuals/fc_10.pdf"
      components:
        - Experimental Chrono-Levitation Chamber (ECLC)
        - Modular Gravitational Displacement Coils (MGDCs)
        - Variable Quantum Flux Transducer (VQFT)
        - Development Time-Space Navigation System (DTNS)

and using require "complex_config/rude" in the "development" environment you can now access the configuration.

Fetching the name of a product:

cc.products.flux_capacitor.enterprise_version.name # => "Flux Capacitor Enterpise"

If the name of configuration file isn't valid ruby method name syntax you can also use cc(:products).flux_capacitor… to avoid this problem.

Fetching the price of a product in cents:

cc.products.flux_capacitor.enterprise_version.price_in_cents # => 160000000

Fetching the price of a product and using the ComplexConfig::Plugins::MONEY plugin to format it:

cc.products.flux_capacitor.enterprise_version.price.format # => "€1,600,000.00"

Fetching the URL of a product manual as a string:

cc.products.flux_capacitor.enterprise_version.manual_pdf_url
  # => "http://brown-inc.com/manuals/fc_enterprise.pdf"

Fetching the URL of a product manual and using the ComplexConfig::Plugins::URI plugin return an URI instance:

cc.products.flux_capacitor.enterprise_version.manual_pdf_uri
  # => #<URI::HTTP:0x007ff626d2a2e8 URL:http://brown-inc.com/manuals/fc_enterprise.pdf>

You can also fetch config settings from a different environment:

pp cc.products(:test); nil

and output them.

products
└─ flux_capacitor
   └─ test_version
      ├─ name = "Yadayada"
      ├─ price_in_cents = 666
      ├─ manual_pdf_url = "http://staging.brown-inc.com/manuals/fc_10.pdf"
      └─ components
         ├─ "Experimental Chrono-Levitation Chamber (ECLC)"
         ├─ "Modular Gravitational Displacement Coils (MGDCs)"
         ├─ "Variable Quantum Flux Transducer (VQFT)"
         └─ "Development Time-Space Navigation System (DTNS)"

Calling complex_config.products. instead of cc(…) would skip the implicit namespacing via the RAILS_ENV environment, so complex_config(:products).test.flux_capacitor returns the same settings object.

ComplexConfig provides robust encryption capabilities for securing sensitive configuration data, with built-in compatibility with Rails' secret encryption system.

The library supports encrypting YAML configuration files using AES-128-GCM encryption. This allows you to store sensitive information like API keys, passwords, and other secrets in your version control without exposing them in plain text.

# Write encrypted configuration
ComplexConfig::Provider.write_config('database', 
  value: { password: 'secret_password' }, 
  encrypt: :random
)
# => Returns the random 128-bit master key as hexadecimal string.

This creates config/database.yml.enc which contains the encrypted data and returns the master key, which you can provide via an environment variable for later read access.

ComplexConfig supports multiple key sources in priority order:

1. Explicit key setting: Direct assignment via config.key = 'your-key'
2. Environment variables: COMPLEX_CONFIG_KEY or RAILS_MASTER_KEY
3. Key files: Files with .key extension alongside encrypted files
4. Master key files: config/master.key (Rails-compatible)

ComplexConfig is fully compatible with Rails' secret encryption system:

# Works seamlessly with Rails master.key
ENV['RAILS_MASTER_KEY'] = '0123456789abcdef0123456789abcdef' # Do not use this key.
# Encrypted files created by Rails can be read by ComplexConfig

The system uses OpenSSL's AES-128-GCM cipher mode which provides both confidentiality and authenticity. The encryption process:

1. Marshals the configuration object into binary format
2. Encrypts using AES-128-GCM with a randomly generated IV
3. Authenticates with an authentication tag to ensure integrity
4. Encodes all components in base64 and combines them with -- separators

• Authenticated Encryption: Ensures data hasn't been tampered with
• Secure Key Handling: Validates key length requirements (16 bytes for AES-128)
• Multiple Sources: Flexible key management for different deployment scenarios
• Atomic Writes: Uses secure file writing to prevent corruption during encryption operations

This approach allows you to maintain sensitive configuration data securely while keeping the same familiar YAML-based workflow that developers expect.

The complex_config executable provides a convenient command-line interface for managing encrypted configuration files. This tool is particularly useful when you need to securely store sensitive configuration data while maintaining easy access during development and deployment.

• Secure File Operations: Encrypts/decrypts configuration files with automatic backup handling
• Edit Support: Opens encrypted files in your preferred editor (EDITOR environment variable or vi by default)
• Key Management: Generates new encryption keys and supports key rotation
• Atomic Writes: Uses secure file writing to prevent data corruption

# Encrypt a configuration file
complex_config encrypt config/database.yml

# Decrypt a configuration file  
complex_config decrypt config/database.yml.enc

# Edit an encrypted configuration file
complex_config edit config/database.yml.enc

# Display decrypted content without writing to disk
complex_config display config/database.yml.enc

# Generate a new encryption key
complex_config new_key

# Recrypt a file with a different key
complex_config recrypt -o OLD_KEY -n NEW_KEY config/database.yml.enc

The script uses symmetric encryption for configuration files. When using encrypted configurations:

1. Key Management: Store your encryption keys securely (never in version control)
2. File Permissions: Ensure encrypted .enc files have appropriate permissions
3. Backup Strategy: The recrypt command automatically creates backup files

When you use the complex_config executable, it works with the same encryption mechanism that ComplexConfig uses internally for its encrypted configuration files. This ensures consistency between your application's configuration loading and your manual encryption/decryption workflows.

The tool is particularly valuable in development environments where you want to maintain sensitive configurations without committing them to version control while still being able to easily edit and manage them during development.

• EDITOR: Sets the preferred text editor for editing encrypted files (defaults to vi)
• COMPLEX_CONFIG_KEY: Can be set to provide a default encryption key

This command-line tool provides a bridge between secure configuration management and practical workflow needs, making it easier to maintain encrypted configurations without sacrificing usability.

ComplexConfig provides several built-in methods for inspecting and debugging configuration data:

To see all available attributes and their values in a structured format:

puts cc.products.flux_capacitor.enterprise_version.attributes_list

This outputs a representation showing all configuration paths and values listed like this:

name = "Flux Capacitor Enterpise"
price_in_cents = 160000000
manual_pdf_url = "http://brown-inc.com/manuals/fc_enterprise.pdf"
components[0] = "Super-Advanced Chrono-Levitation Chamber (SACL)"
components[1] = "Quadruple Gravitational Displacement Coils (QGDCs)"
components[2] = "Ultra-Advanced Quantum Flux Transducer (UAQFT)"
components[3] = "Enterprise Time-Space Navigation System (ETNS)"

For a more visual representation of the configuration hierarchy:

puts cc.products.flux_capacitor.enterprise_version

This displays the configuration in a tree format:

products.flux_capacitor.enterprise_version
├─ name = "Flux Capacitor Enterpise"
├─ price_in_cents = 160000000
├─ manual_pdf_url = "http://brown-inc.com/manuals/fc_enterprise.pdf"
└─ components
   ├─ "Super-Advanced Chrono-Levitation Chamber (SACL)"
   ├─ "Quadruple Gravitational Displacement Coils (QGDCs)"
   ├─ "Ultra-Advanced Quantum Flux Transducer (UAQFT)"
   └─ "Enterprise Time-Space Navigation System (ETNS)"

These debugging methods are particularly useful during development when you need to verify that your configuration files are loaded correctly and contain the expected values.

ComplexConfig provides a comprehensive error handling system with specific exceptions for different failure scenarios, following Ruby conventions for predictable behavior.

The library defines a clear exception hierarchy that inherits from ComplexConfig::ComplexConfigError:

classDiagram
    class ComplexConfigError {
        <<abstract>>
        +message
    }

    class AttributeMissing
    class ConfigurationFileMissing
    class ConfigurationSyntaxError
    class EncryptionError {
        <<abstract>>
    }
    class EncryptionKeyInvalid
    class EncryptionKeyMissing
    class DecryptionFailed

    ComplexConfigError <|-- AttributeMissing
    ComplexConfigError <|-- ConfigurationFileMissing
    ComplexConfigError <|-- ConfigurationSyntaxError
    ComplexConfigError <|-- EncryptionError
    EncryptionError <|-- EncryptionKeyInvalid
    EncryptionError <|-- EncryptionKeyMissing
    EncryptionError <|-- DecryptionFailed

When a configuration file is missing, ConfigurationFileMissing is raised. This includes both regular .yml files and encrypted .yml.enc files:

# Raises ComplexConfig::ConfigurationFileMissing if config/products.yml doesn't exist
cc.products.flux_capacitor.enterprise_version.name

Invalid YAML syntax in configuration files raises ConfigurationSyntaxError, which wraps the underlying Psych::SyntaxError to provide context:

# Raises ComplexConfig::ConfigurationSyntaxError for malformed YAML
cc.products # ... with invalid YAML content

Accessing non-existent attributes raises AttributeMissing:

# Raises ComplexConfig::AttributeMissing if 'nonexistent_attribute' doesn't exist
cc.products.nonexistent_attribute

When using encrypted configuration files without proper encryption keys, EncryptionKeyMissing is raised:

# Raises ComplexConfig::EncryptionKeyMissing when no key is available for .enc files
cc.products # ... with encrypted config but missing key

ComplexConfig supports safe access patterns to avoid exceptions in conditional contexts:

# Using method names ending with '?' returns nil instead of raising exceptions
cc.products?(:test)        # Returns nil if 'test' environment doesn't exist
cc.products.flux_capacitor.enterprise_version.name?  # Returns nil if name attribute missing

# Safe access to configuration that may not exist
if cc.products?(:test)
  # Safe to access test config here
end

For robust applications, consider wrapping critical configuration access in exception handlers:

begin
  price = cc.products.flux_capacitor.enterprise_version.price_in_cents
rescue ComplexConfig::ConfigurationFileMissing => e
  Rails.logger.warn "Configuration file missing: #{e.message}"
  # Provide default value or fallback behavior
rescue ComplexConfig::ConfigurationSyntaxError => e
  Rails.logger.error "Invalid YAML in configuration: #{e.message}"
  # Handle invalid syntax appropriately
end

The error handling system ensures that configuration loading and access failures are predictable and can be handled gracefully by application code.

You can complex_config by passing a block to its configure method, which you can for example do in a rails config/initializers file:

ComplexConfig.configure do |config|
  # Allow modification during tests b/c of stubs etc.
  config.deep_freeze = !Rails.env.test?

  # config.env = 'some_environment'

  # config.config_dir = Rails.root + 'config'

  config.add_plugin -> id do
    if base64_string = ask_and_send("#{id}_base64")
      Base64.decode64 base64_string
    else
      skip
    end
  end
end

• #env: Explicitly sets the environment instead of auto-detecting from RAILS_ENV

• #config_dir: Changes the directory where configuration files are loaded from instead of using the default config folder

• add_plugin registers custom lambdas that can transform configuration values at runtime, allowing for intelligent data processing like base64 decoding or automatic type conversion when accessing config attributes. See Adding plugins below.

📝 Note the deep_freeze setting, that is just enabled during testing and is explained in the next section.

The deep_freeze setting controls whether configuration objects are deeply frozen after initialization. When enabled (default), this provides several important benefits:

• Immutability: Configuration values cannot be modified after loading, preventing accidental runtime changes 🚫
• Thread Safety: Frozen configurations can be safely shared across threads without synchronization 🔄
• Security: Protects against runtime tampering of critical configuration data 🔒

• Memory Efficiency: Ruby's garbage collector can optimize frozen objects more effectively 🧠
• Cache Efficiency: Immutable objects can be cached more aggressively 💾
• CPU Optimization: Ruby's internal optimizations for frozen objects can provide performance improvements, if configuration settings are accessed often. ⚙️
• Predictable Behavior: Eliminates potential race conditions and state corruption 🧭

In test environments, you might disable deep freezing to allow for easier testing and modification:

ComplexConfig.configure do |config|
  config.deep_freeze = false
end

This setting is particularly important in production environments where configuration stability and performance are paramount.

You can add your own plugins by calling

ComplexConfig::Provider.add_plugin SomeNamespace::PLUGIN

or in the configuration block by calling

ComplexConfig.configure do |config|
  config.add_plugin SomeNamespace::PLUGIN
end

A plugin is just a lambda expression with a single argument id which identifies the attribute that is being accessed. If it calls skip it won't apply and the following plugins are tried until one doesn't call skip and returns a value instead.

Here is the ComplexConfig::Plugins::MONEY plugin for example:

require 'monetize'

module ComplexConfig::Plugins
  MONEY = -> id do
    if cents = ask_and_send("#{id}_in_cents")
      Money.new(cents)
    else
      skip
    end
  end
end

The homepage of this library is located at

• https://github.com/flori/complex_config

Florian Frank

This software is licensed under the Apache 2.0 license.