Module: ComputedModel::ClassMethods

Defined in:
lib/computed_model.rb

Overview

A set of class methods for ComputedModel. Automatically included to the singleton class when you include ComputedModel.

Instance Method Summary collapse

Instance Method Details

#bulk_load_and_compute(deps, **options) ⇒ Array<Object>

The core routine for batch-loading.

Parameters:

  • deps (Array<Symbol, Hash{Symbol=>Array}>) —

    A set of dependencies.

  • options (Hash) —

    An arbitrary hash to pass to loaders defined by #define_loader.

Returns:

  • (Array<Object>) —

    The array of the requested models. Based on what the primary loader returns.



227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
 
# File 'lib/computed_model.rb', line 227

def bulk_load_and_compute(deps, **options)
  unless @__computed_model_primary_attribute
    raise ArgumentError, "No primary loader defined"
  end

  objs = orig_objs = nil
  plan = computing_plan(deps)
  plan.load_order.each do |dep_name|
    if @__computed_model_primary_attribute == dep_name
      orig_objs = @__computed_model_primary_loader.call(plan.subdeps_hash[dep_name], **options)
      objs = orig_objs.dup
    elsif @__computed_model_dependencies.key?(dep_name)
      raise "Bug: objs is nil" if objs.nil?

      objs.each do |obj|
        obj.send(:"compute_#{dep_name}")
      end
    elsif @__computed_model_loaders.key?(dep_name)
      raise "Bug: objs is nil" if objs.nil?

      l = @__computed_model_loaders[dep_name]
      keys = objs.map { |o| o.instance_exec(&(l.key_proc)) }
      subobj_by_key = l.load_proc.call(keys, plan.subdeps_hash[dep_name], **options)
      objs.zip(keys) do |obj, key|
        obj.send(:"#{dep_name}=", subobj_by_key[key])
      end
    else
      raise "No dependency info for #{self}##{dep_name}"
    end
    objs.reject! { |obj| !obj.computed_model_error.nil? }
  end

  orig_objs
end

#computed(meth_name) ⇒ Symbol

Declares a computed attribute. See #dependency too.

Examples:

define a field which is calculated from loaded models

dependency :user, :user_external_resource
computed def something
  # Use user and user_external_resource ...
end

Parameters:

  • meth_name (Symbol) —

    a method name to promote to a computed attribute. Typically used in the form of computed def ....

Returns:

  • (Symbol) —

    passes through the argument.



76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
 
# File 'lib/computed_model.rb', line 76

def computed(meth_name)
  var_name = :"@#{meth_name}"
  meth_name_orig = :"#{meth_name}_orig"
  compute_meth_name = :"compute_#{meth_name}"

  @__computed_model_dependencies[meth_name] = ComputedModel.normalize_dependencies(@__computed_model_next_dependency)
  remove_instance_variable(:@__computed_model_next_dependency)

  alias_method meth_name_orig, meth_name
  define_method(meth_name) do
    raise NotLoaded, "the field #{meth_name} is not loaded" unless instance_variable_defined?(var_name)
    instance_variable_get(var_name)
  end
  define_method(compute_meth_name) do
    instance_variable_set(var_name, send(meth_name_orig))
  end
  if public_method_defined?(meth_name_orig)
    public meth_name
  elsif protected_method_defined?(meth_name_orig)
    protected meth_name
  elsif private_method_defined?(meth_name_orig)
    private meth_name
  end

  meth_name
end

#computing_plan(deps) ⇒ Plan

Parameters:

  • deps (Array)

Returns:



264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
 
# File 'lib/computed_model.rb', line 264

def computing_plan(deps)
  normalized = ComputedModel.normalize_dependencies(deps)
  load_order = []
  subdeps_hash = {}
  visiting = Set[]
  visited = Set[]
  if @__computed_model_primary_attribute
    load_order << @__computed_model_primary_attribute
    visiting.add @__computed_model_primary_attribute
    visited.add @__computed_model_primary_attribute
    subdeps_hash[@__computed_model_primary_attribute] ||= []
  end
  normalized.each do |dep_name, dep_subdeps|
    computing_plan_dfs(dep_name, dep_subdeps, load_order, subdeps_hash, visiting, visited)
  end

  Plan.new(load_order, subdeps_hash)
end

#define_loader(meth_name, key:) {|keys, subdeps, **options| ... } ⇒ void

This method returns an undefined value.

Declares a loaded attribute. See #dependency and #define_primary_loader too.

define_loader :foo do ... end generates a reader foo and a writer foo=. The writer is only meant to be used in the loader.

The responsibility of loader is to call foo= for all the given objects, or set computed_model_error otherwise.

Examples:

define a loader for ActiveRecord-based models

define_loader :user_aux_data, key: -> { id } do |user_ids, subdeps, **options|
  UserAuxData.where(user_id: user_ids).preload(subdeps).group_by(&:id)
end

Parameters:

  • meth_name (Symbol) —

    the name of the loaded attribute.

  • key (Proc) —

    The proc to collect keys.

Yields:

  • (keys, subdeps, **options)

Yield Parameters:

  • objects (Array) —

    The ids of the loaded attributes.

  • subdeps (Hash) —

    sub-dependencies

  • options (Hash) —

    A verbatim copy of what is passed to #bulk_load_and_compute.

Yield Returns:

  • (Hash)

Raises:

  • (ArgumentError) 


165
166
167
168
169
170
171
172
173
174
175
176
177
 
# File 'lib/computed_model.rb', line 165

def define_loader(meth_name, key:, &block)
  raise ArgumentError, "No block given" unless block

  var_name = :"@#{meth_name}"

  @__computed_model_loaders[meth_name] = Loader.new(key, block)

  define_method(meth_name) do
    raise NotLoaded, "the field #{meth_name} is not loaded" unless instance_variable_defined?(var_name)
    instance_variable_get(var_name)
  end
  attr_writer meth_name
end

#define_primary_loader(meth_name) {|**options| ... } ⇒ void

This method returns an undefined value.

Declares a primary attribute. See #define_loader and #dependency too.

define_primary_loader :foo do ... end generates a reader foo and a writer foo=. The writer is only meant to be used in the loader.

The responsibility of the primary loader is to list up all the relevant primary models, and initialize instances of the subclass of ComputedModel with @foo set to the primary model which is just being found.

Examples:

define a loader for ActiveRecord-based models

define_loader :raw_user do |users, subdeps, **options|
  user_ids = users.map(&:id)
  raw_users = RawUser.where(id: user_ids).preload(subdeps).index_by(&:id)
  users.each do |user|
    # Even if it doesn't exist, you must explicitly assign nil to the field.
    user.raw_user = raw_users[user.id]
  end
end

Parameters:

  • meth_name (Symbol) —

    the name of the loaded attribute.

Yields:

  • (**options)

Yield Parameters:

Yield Returns:

  • (void)

Raises:

  • (ArgumentError) 


204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
 
# File 'lib/computed_model.rb', line 204

def define_primary_loader(meth_name, &block)
  raise ArgumentError, "No block given" unless block
  raise ArgumentError, "Primary loader has already been defined" if @__computed_model_primary_attribute

  var_name = :"@#{meth_name}"

  @__computed_model_primary_loader = block
  @__computed_model_primary_attribute = meth_name

  define_method(meth_name) do
    raise NotLoaded, "the field #{meth_name} is not loaded" unless instance_variable_defined?(var_name)
    instance_variable_get(var_name)
  end
  attr_writer meth_name
end

#delegate_dependency(*methods, to:, allow_nil: nil, prefix: nil, include_subdeps: nil) ⇒ void

This method returns an undefined value.

A shorthand for simple computed attributes.

Use #computed for more complex definition.

Examples:

delegate name from raw_user

delegate_dependency :name, to: :raw_user

delegate name from raw_user, but expose as user_name

delegate_dependency :name, to: :raw_user, prefix: :user

Parameters:

  • methods (Array<Symbol>) —

    method names to delegate

  • to (Symbol) —

    which attribute to delegate the methods to. This parameter is used for the dependency declaration too.

  • allow_nil (nil, Boolean) (defaults to: nil) —

    If true, nil receivers are is ignored, and nil is returned instead.

  • prefix (nil, Symbol) (defaults to: nil) —

    A prefix for the delegating method name.

  • include_subdeps (nil, Boolean) (defaults to: nil) —

    If true, sub-dependencies are also included.



122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
 
# File 'lib/computed_model.rb', line 122

def delegate_dependency(*methods, to:, allow_nil: nil, prefix: nil, include_subdeps: nil)
  method_prefix = prefix ? "#{prefix}_" : ""
  methods.each do |meth_name|
    pmeth_name = :"#{method_prefix}#{meth_name}"
    if include_subdeps
      dependency to=>meth_name
    else
      dependency to
    end
    if allow_nil
      define_method(pmeth_name) do
        send(to)&.public_send(meth_name)
      end
    else
      define_method(pmeth_name) do
        send(to).public_send(meth_name)
      end
    end
    computed pmeth_name
  end
end

#dependency(*deps) ⇒ void

This method returns an undefined value.

Declares the dependency of a computed attribute. See #computed too.

Examples:

declaring dependencies

dependency :user, :user_external_resource
computed def something
  # Use user and user_external_resource ...
end

declaring dependencies with sub-dependencies

dependency user: [:user_names, :premium], user_external_resource: [:received_stars]
computed def something
  # Use user and user_external_resource ...
end

Parameters:

  • deps (Array<Symbol, Hash{Symbol=>Array}>) —

    Dependency description. If a symbol :foo is given, it's interpreted as { foo: [] }. When the same symbol occurs multiple times, the array is concatenated. The contents of the array (called "sub-dependency") is treated opaquely by the computed_model gem. It is up to the user to design the format of sub-dependencies.



60
61
62
63
 
# File 'lib/computed_model.rb', line 60

def dependency(*deps)
  @__computed_model_next_dependency ||= []
  @__computed_model_next_dependency.push(*deps)
end