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Merge pull request #44507 from jonathanhefner/apidocs-improve-active_…
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…record-serialize-doc

Improve `serialize` API doc [ci-skip]
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@jonathanhefner
jonathanhefner committed Feb 23, 2022
2 parents 8e080d0 + 29b2a57 commit 4878741
Showing 1 changed file with 34 additions and 50 deletions.
84 changes: 34 additions & 50 deletions activerecord/lib/active_record/attribute_methods/serialization.rb
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Expand Up @@ -24,38 +24,6 @@ module ClassMethods
# The serialization format may be YAML, JSON, or any custom format using a
# custom coder class.
#
# === Serialization formats
#
# serialize attr_name [, class_name_or_coder]
#
# | | database storage |
# class_name_or_coder | attribute read/write type | serialized | NULL |
# ---------------------+---------------------------+------------+--------+
# <not given> | any value that supports | YAML | |
# | .to_yaml | | |
# | | | |
# Array | Array ** | YAML | [] |
# | | | |
# Hash | Hash ** | YAML | {} |
# | | | |
# JSON | any value that supports | JSON | |
# | .to_json | | |
# | | | |
# <custom coder class> | any value supported by | custom | custom |
# | the custom coder class | | |
#
# ** If +class_name_or_coder+ is +Array+ or +Hash+, values retrieved will
# always be of that type, and any value assigned must be of that type or
# +SerializationTypeMismatch+ will be raised.
#
# ==== Custom coders
# A custom coder class or module may be given. This must have +self.load+
# and +self.dump+ class/module methods. <tt>self.dump(object)</tt> will be called
# to serialize an object and should return the serialized value to be
# stored in the database (+nil+ to store as +NULL+). <tt>self.load(string)</tt>
# will be called to reverse the process and load (unserialize) from the
# database.
#
# Keep in mind that database adapters handle certain serialization tasks
# for you. For instance: +json+ and +jsonb+ types in PostgreSQL will be
# converted between JSON object/array syntax and Ruby +Hash+ or +Array+
Expand All @@ -67,55 +35,71 @@ module ClassMethods
#
# ==== Parameters
#
# * +attr_name+ - The field name that should be serialized.
# * +class_name_or_coder+ - Optional, may be be +Array+ or +Hash+ or
# +JSON+ or a custom coder class or module which responds to +.load+
# and +.dump+. See table above.
# * +attr_name+ - The name of the attribute to serialize.
# * +class_name_or_coder+ - Optional. May be one of the following:
# * <em>default</em> - The attribute value will be serialized as YAML.
# The attribute value must respond to +to_yaml+.
# * +Array+ - The attribute value will be serialized as YAML, but an
# empty +Array+ will be serialized as +NULL+. The attribute value
# must be an +Array+.
# * +Hash+ - The attribute value will be serialized as YAML, but an
# empty +Hash+ will be serialized as +NULL+. The attribute value
# must be a +Hash+.
# * +JSON+ - The attribute value will be serialized as JSON. The
# attribute value must respond to +to_json+.
# * <em>custom coder</em> - The attribute value will be serialized
# using the coder's <tt>dump(value)</tt> method, and will be
# deserialized using the coder's <tt>load(string)</tt> method. The
# +dump+ method may return +nil+ to serialize the value as +NULL+.
#
# ==== Options
#
# +default+ The default value to use when no value is provided. If this option
# is not passed, the previous default value (if any) will be used.
# Otherwise, the default will be +nil+.
# * +:default+ - The default value to use when no value is provided. If
# this option is not passed, the previous default value (if any) will
# be used. Otherwise, the default will be +nil+.
#
# ==== Examples
#
# ==== Example
# ===== Serialize the +preferences+ attribute using YAML
#
# # Serialize a preferences attribute using YAML coder.
# class User < ActiveRecord::Base
# serialize :preferences
# end
#
# # Serialize preferences using JSON as coder.
# ===== Serialize the +preferences+ attribute using JSON
#
# class User < ActiveRecord::Base
# serialize :preferences, JSON
# end
#
# # Serialize preferences as Hash using YAML coder.
# ===== Serialize the +preferences+ +Hash+ using YAML
#
# class User < ActiveRecord::Base
# serialize :preferences, Hash
# end
#
# # Serialize preferences using a custom coder.
# ===== Serialize the +preferences+ attribute using a custom coder
#
# class Rot13JSON
# def self.rot13(string)
# string.tr("a-zA-Z", "n-za-mN-ZA-M")
# end
#
# # returns serialized string that will be stored in the database
# def self.dump(object)
# ActiveSupport::JSON.encode(object).rot13
# # Serializes an attribute value to a string that will be stored in the database.
# def self.dump(value)
# rot13(ActiveSupport::JSON.dump(value))
# end
#
# # reverses the above, turning the serialized string from the database
# # back into its original value
# # Deserializes a string from the database to an attribute value.
# def self.load(string)
# ActiveSupport::JSON.decode(string.rot13)
# ActiveSupport::JSON.load(rot13(string))
# end
# end
#
# class User < ActiveRecord::Base
# serialize :preferences, Rot13JSON
# end
#
def serialize(attr_name, class_name_or_coder = Object, **options)
# When ::JSON is used, force it to go through the Active Support JSON encoder
# to ensure special objects (e.g. Active Record models) are dumped correctly
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