DynamoDB Dynomite Field

The fields and field methods are how you declare fields.

app/models/product.rb

class Product < ApplicationItem
  fields :category,
         :sku,
         :name,
         :price, type: :integer
  field :stock_quantity, type: :integer, default: 1
  field :ttl, type: :integer, default: -> { 1.hour.from_now.to_i }
  field :sold_at, type: :time
end

You can use the fields method to declare multiple fields at the same time.

You can also use the field method to declare each field and provide additional options like type and default.

  • The type option does additional typecasting. See: Typecasting
  • The default option can accept a Proc or symbol for a method name to be called.

Undeclared Fields Behavior

If you assign values directly to attributes on undeclared model fields like so:

post = Post.first
post.attributes[:foo] = "bar" # foo is not a declared field
post.save # dynomite does some checking

Dynomite will process them in different ways.

  1. warn: Removes the undeclared attributes but logs a warning.
  2. silent: Silently remove the undeclared attributes. This prevents “dirty” data from getting your table from a mass assignment.
  3. error: Raises an error.
  4. allow: Allows the undeclared attributes to be assigned.

The default behavior is warn. Dynomite checks for declared fields upon saving the item.

You can configure the behavior with:

config/initializers/dynomite.rb

Dynomite.configure do |config|
  # available: warn silent error allow
  config.undeclared_field_behavior = :warn # default: will remove the attributes and log a warning
end

On the reading side, with attributes that do not have a field declaration, you can access and read it by reading the attribute via more direct methods:

  • Hash notation: post[:foo]
  • attributes: attributes[:foo]
  • read_attribute: read_attribute(:foo)

Since there is no field declaration, no dot method is available. You are directly accessing and setting attributes.

It’s recommended to use field declarations for clarity.

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