Class: JSI::JSICoder

Inherits:
Object
  • Object
show all
Defined in:
lib/jsi/jsi_coder.rb

Overview

this is an ActiveRecord serialization coder intended to serialize between JSON-compatible objects on the database side, and a JSI instance loaded on the model attribute.

on its own this coder is useful with a JSON database column. in order to serialize further to a string of JSON, or to YAML, the gem arms allows coders to be chained together. for example, for a table foos and a column preferences_json which is an actual json column, and preferences_txt which is a string:

Preferences = JSI.new_schema_module(preferences_json_schema)
class Foo < ActiveRecord::Base
  # as a single serializer, loads a Preferences instance from a json column
  serialize 'preferences_json', JSI::JSICoder.new(Preferences)

  # for a text column, arms_serialize will go from JSI to JSON-compatible
  # objects to a string. the symbol `:jsi` is a shortcut for JSI::JSICoder.
  arms_serialize 'preferences_txt', [:jsi, Preferences], :json
end

the column data may be either a single instance of the schema class (represented as one json object) or an array of them (represented as a json array of json objects), indicated by the keyword argument array.

Instance Method Summary collapse

Constructor Details

#initialize(schema, array: false) ⇒ JSICoder

Returns a new instance of JSICoder.

Parameters:

  • schema (#new_jsi) —

    a Schema, SchemaSet, or JSI schema module. #load will instantiate column data using the JSI schemas represented.

  • array (Boolean) (defaults to: false) —

    whether the dumped data represent one instance of the schema, or an array of them. note that it may be preferable to simply use an array schema.



32
33
34
35
36
37
38
 
# File 'lib/jsi/jsi_coder.rb', line 32

def initialize(schema, array: false)
  unless schema.respond_to?(:new_jsi)
    raise(ArgumentError, "schema param does not respond to #new_jsi: #{schema.inspect}")
  end
  @schema = schema
  @array = array
end

Instance Method Details

#dump(object) ⇒ Object, ...

dumps the object for the database

Parameters:

  • object (JSI::Base, Array<JSI::Base>, nil) —

    the JSI or array of JSIs containing the schema instance(s)

Returns:

  • (Object, Array, nil) —

    the schema instance(s) of the JSI(s), or nil if object is nil



62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
 
# File 'lib/jsi/jsi_coder.rb', line 62

def dump(object)
  return nil if object.nil?
  jsonifiable = begin
    if @array
      unless object.respond_to?(:to_ary)
        raise(TypeError, "expected array-like attribute; got: #{object.class}: #{object.inspect}")
      end
      object.to_ary.map do |el|
        dump_object(el)
      end
    else
      dump_object(object)
    end
  end
  jsonifiable
end

#load(data) ⇒ JSI::Base, ...

loads the database column to JSI instances of our schema

Parameters:

  • data (Object, Array, nil) —

    the dumped schema instance(s) of the JSI(s)

Returns:

  • (JSI::Base, Array<JSI::Base>, nil) —

    the JSI or JSIs containing the schema instance(s), or nil if data is nil



45
46
47
48
49
50
51
52
53
54
55
56
 
# File 'lib/jsi/jsi_coder.rb', line 45

def load(data)
  return nil if data.nil?
  object = if @array
    unless data.respond_to?(:to_ary)
      raise TypeError, "expected array-like column data; got: #{data.class}: #{data.inspect}"
    end
    data.to_ary.map { |el| load_object(el) }
  else
    load_object(data)
  end
  object
end