Merge pull request #1 from Syati/error_format

Improve error handling and serialization features

Author: Syati

README.md

@@ -11,238 +11,83 @@ English | [日本語](README_ja.md)
 - **Array handling** for both primitive types and nested objects  
 - **Strong Parameters integration** with automatic permit lists
 - **ActiveModel compatibility** with validations and serialization
+- **Enhanced error handling** with flat and structured formats
 - **RBS type definitions** for better development experience
 
-## Installation
-
-Add this line to your application's Gemfile:
+## Quick Start
 
 ```ruby
+# 1. Install the gem
 gem 'structured_params'
-```
-
-And then execute:
-
-```bash
-$ bundle install
-```
-
-Or install it yourself as:
-
-```bash
-$ gem install structured_params
-```
-
-## Setup
 
-Register the custom types in your Rails application:
-
-```ruby
-# config/initializers/structured_params.rb
+# 2. Register types in initializer
 StructuredParams.register_types
-```
-
-This registers `:object` and `:array` types with ActiveModel::Type.
-
-## Usage
 
-### Basic Parameter Class
-
-```ruby
+# 3. Define parameter classes
 class UserParams < StructuredParams::Params
   attribute :name, :string
   attribute :age, :integer
-  attribute :email, :string
+  attribute :address, :object, value_class: AddressParams
+  attribute :hobbies, :array, value_class: HobbyParams
 
   validates :name, presence: true
-  validates :email, format: { with: URI::MailTo::EMAIL_REGEXP }
+  validates :age, numericality: { greater_than: 0 }
 end
 
-# Usage in controller
+# 4. Use in controllers
 def create
   user_params = UserParams.new(params[:user])
   if user_params.valid?
     User.create!(user_params.attributes)
   else
-    render json: { errors: user_params.errors }
+    render json: { errors: user_params.errors.to_hash(false, structured: true) }
   end
 end
 ```
 
-### Nested Objects
+## Documentation
+
+- **[Installation and Setup](docs/installation.md)** - Getting started with StructuredParams
+- **[Basic Usage](docs/basic-usage.md)** - Parameter classes, nested objects, and arrays
+- **[Validation](docs/validation.md)** - Using ActiveModel validations with nested structures
+- **[Strong Parameters](docs/strong-parameters.md)** - Automatic permit list generation
+- **[Error Handling](docs/error-handling.md)** - Flat and structured error formats
+- **[Serialization](docs/serialization.md)** - Converting parameters to hashes and JSON
+- **[Advanced Usage](docs/advanced-usage.md)** - Type introspection, performance tips, and more
+
+## Example
 
 ```ruby
 class AddressParams < StructuredParams::Params
   attribute :street, :string
   attribute :city, :string
   attribute :postal_code, :string
+  
+  validates :street, :city, :postal_code, presence: true
 end
 
 class UserParams < StructuredParams::Params
   attribute :name, :string
+  attribute :email, :string
   attribute :address, :object, value_class: AddressParams
+  
+  validates :name, presence: true
+  validates :email, format: { with: URI::MailTo::EMAIL_REGEXP }
 end
 
 # Usage
 params = {
   name: "John Doe",
-  address: {
-    street: "123 Main St",
-    city: "New York",
-    postal_code: "10001"
-  }
+  email: "john@example.com",
+  address: { street: "123 Main St", city: "New York", postal_code: "10001" }
 }
 
 user_params = UserParams.new(params)
-user_params.address # => AddressParams instance
+user_params.valid? # => true
 user_params.address.city # => "New York"
+user_params.attributes # => Hash ready for ActiveRecord
 ```
 
-### Arrays
-
-#### Array of Primitive Types
-
-```ruby
-class UserParams < StructuredParams::Params
-  attribute :tags, :array, value_type: :string
-  attribute :scores, :array, value_type: :integer
-end
-
-# Usage
-params = {
-  tags: ["ruby", "rails", "programming"],
-  scores: [85, 92, 78]
-}
-
-user_params = UserParams.new(params)
-user_params.tags # => ["ruby", "rails", "programming"]
-user_params.scores # => [85, 92, 78]
-```
-
-#### Array of Nested Objects
-
-```ruby
-class HobbyParams < StructuredParams::Params
-  attribute :name, :string
-  attribute :level, :string
-end
-
-class UserParams < StructuredParams::Params
-  attribute :name, :string
-  attribute :hobbies, :array, value_class: HobbyParams
-end
-
-# Usage
-params = {
-  name: "Alice",
-  hobbies: [
-    { name: "Photography", level: "beginner" },
-    { name: "Cooking", level: "intermediate" }
-  ]
-}
-
-user_params = UserParams.new(params)
-user_params.hobbies # => [HobbyParams, HobbyParams]
-user_params.hobbies.first.name # => "Photography"
-```
-
-### Strong Parameters Integration
-
-StructuredParams automatically generates permit lists for Strong Parameters:
-
-```ruby
-class UsersController < ApplicationController
-  def create
-    permitted_params = params.require(:user).permit(*UserParams.permit_attribute_names)
-    user_params = UserParams.new(permitted_params)
-    
-    if user_params.valid?
-      User.create!(user_params.attributes)
-    else
-      render json: { errors: user_params.errors }
-    end
-  end
-end
-
-# UserParams.permit_attribute_names returns:
-# [:name, :age, :email, { address: [:street, :city, :postal_code] }, { hobbies: [:name, :level] }]
-```
-
-### Validation
-
-Since StructuredParams inherits from ActiveModel, you can use all ActiveModel validations:
-
-```ruby
-class UserParams < StructuredParams::Params
-  attribute :name, :string
-  attribute :age, :integer
-  attribute :email, :string
-  attribute :address, :object, value_class: AddressParams
-  
-  validates :name, presence: true, length: { minimum: 2 }
-  validates :age, presence: true, numericality: { greater_than: 0 }
-  validates :email, presence: true, format: { with: URI::MailTo::EMAIL_REGEXP }
-  validates :address, presence: true
-  
-  validate :custom_validation
-  
-  private
-  
-  def custom_validation
-    errors.add(:age, "must be adult") if age && age < 18
-  end
-end
-```
-
-### Serialization
-
-```ruby
-user_params = UserParams.new(params)
-user_params.attributes # => Hash with all attributes
-user_params.to_json    # => JSON string
-```
-
-## Advanced Usage
-
-### Custom Type Registration
-
-If you want to avoid potential naming conflicts, you can register types with custom names:
-
-```ruby
-# Register with custom names
-StructuredParams.register_types_as(
-  object_name: :structured_object,
-  array_name: :structured_array
-)
-
-# Then use in your parameter classes
-class UserParams < StructuredParams::Params
-  attribute :address, :structured_object, value_class: AddressParams
-  attribute :hobbies, :structured_array, value_class: HobbyParams
-end
-```
-
-### Type Introspection
-
-```ruby
-user_params = UserParams.new(params)
-
-# Check attribute types
-UserParams.attribute_types[:name].type        # => :string
-UserParams.attribute_types[:address].type     # => :object
-UserParams.attribute_types[:hobbies].type     # => :array
-
-# Access nested value classes
-UserParams.attribute_types[:address].value_class  # => AddressParams
-UserParams.attribute_types[:hobbies].value_class  # => HobbyParams
-```
-
-## Development
-
-After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
-
-To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and the created tag, and push the `.gem` file to [rubygems.org](https://rubygems.org).
-
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/Syati/structured_params.