Class: GraphQL::Schema::Resolver

Inherits:
Object
  • Object
show all
Extended by:
Member::BaseDSLMethods, Member::HasArguments, Member::HasPath
Includes:
Member::GraphQLTypeNames, Member::HasPath
Defined in:
lib/graphql/schema/resolver.rb,
lib/graphql/schema/resolver/has_payload_type.rb

Overview

A class-based container for field configuration and resolution logic. It supports:

  • Arguments, via .argument(...) helper, which will be applied to the field.
  • Return type, via .type(..., null: ...), which will be applied to the field.
  • Description, via .description(...), which will be applied to the field
  • Resolution, via #resolve(**args) method, which will be called to resolve the field.
  • #object and #context accessors for use during #resolve.

Resolvers can be attached with the resolver: option in a field(...) call.

A resolver’s configuration may be overridden with other keywords in the field(...) call.

See the Resolver.field_options to see how a Resolver becomes a set of field configuration options.

See Also:

  • for a concrete subclass of `Resolver`.
  • `Resolver` is a replacement for `GraphQL::Function`

Direct Known Subclasses

Mutation, Subscription

Defined Under Namespace

Modules: HasPayloadType

Constant Summary

Constants included from Member::GraphQLTypeNames

Member::GraphQLTypeNames::Boolean, Member::GraphQLTypeNames::ID, Member::GraphQLTypeNames::Int

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Member::HasPath

path

Methods included from Member::HasArguments

add_argument, argument, argument_class, arguments, own_arguments

Methods included from Member::BaseDSLMethods

accessible?, default_graphql_name, description, graphql_name, introspection, introspection?, mutation, name, overridden_graphql_name, to_graphql, visible?

Constructor Details

#initialize(object:, context:, field:) ⇒ Resolver

Returns a new instance of Resolver

Parameters:



33
34
35
36
37
38
39
40
41
42
43
 
# File 'lib/graphql/schema/resolver.rb', line 33

def initialize(object:, context:, field:)
  @object = object
  @context = context
  @field = field
  # Since this hash is constantly rebuilt, cache it for this call
  @arguments_by_keyword = {}
  self.class.arguments.each do |name, arg|
    @arguments_by_keyword[arg.keyword] = arg
  end
  @arguments_loads_as_type = self.class.arguments_loads_as_type
end

Instance Attribute Details

#context ⇒ GraphQL::Query::Context (readonly)

Returns:



49
50
51
 
# File 'lib/graphql/schema/resolver.rb', line 49

def context
  @context
end

#field ⇒ GraphQL::Schema::Field (readonly)

Returns:



52
53
54
 
# File 'lib/graphql/schema/resolver.rb', line 52

def field
  @field
end

#object ⇒ Object (readonly)

Returns The application object this field is being resolved on

Returns:

  • (Object) —

    The application object this field is being resolved on



46
47
48
 
# File 'lib/graphql/schema/resolver.rb', line 46

def object
  @object
end

Class Method Details

.argument(*args, **kwargs, &block) ⇒ Object

Add an argument to this field’s signature, but also add some preparation hook methods which will be used for this argument

See Also:

  • for the signature


287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
 
# File 'lib/graphql/schema/resolver.rb', line 287

def argument(*args, **kwargs, &block)
  loads = kwargs[:loads]
  # Use `from_resolver: true` to short-circuit the InputObject's own `loads:` implementation
  # so that we can support `#load_{x}` methods below.
  arg_defn = super(*args, from_resolver: true, **kwargs)
  own_arguments_loads_as_type[arg_defn.keyword] = loads if loads

  if loads && arg_defn.type.list?
    class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def load_#{arg_defn.keyword}(values)
      argument = @arguments_by_keyword[:#{arg_defn.keyword}]
      lookup_as_type = @arguments_loads_as_type[:#{arg_defn.keyword}]
      context.schema.after_lazy(values) do |values2|
        GraphQL::Execution::Lazy.all(values2.map { |value| load_application_object(argument, lookup_as_type, value) })
      end
    end
    RUBY
  elsif loads
    class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def load_#{arg_defn.keyword}(value)
      argument = @arguments_by_keyword[:#{arg_defn.keyword}]
      lookup_as_type = @arguments_loads_as_type[:#{arg_defn.keyword}]
      load_application_object(argument, lookup_as_type, value)
    end
    RUBY
  else
    class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def load_#{arg_defn.keyword}(value)
      value
    end
    RUBY
  end

  arg_defn
end

.arguments_loads_as_type ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



324
325
326
327
 
# File 'lib/graphql/schema/resolver.rb', line 324

def arguments_loads_as_type
  inherited_lookups = superclass.respond_to?(:arguments_loads_as_type) ? superclass.arguments_loads_as_type : {}
  inherited_lookups.merge(own_arguments_loads_as_type)
end

.complexity(new_complexity = nil) ⇒ Integer, Proc

Specifies the complexity of the field. Defaults to 1

Returns:

  • (Integer, Proc) 


258
259
260
261
262
263
 
# File 'lib/graphql/schema/resolver.rb', line 258

def complexity(new_complexity = nil)
  if new_complexity
    @complexity = new_complexity
  end
  @complexity || (superclass.respond_to?(:complexity) ? superclass.complexity : 1)
end

.extension(extension, **options) ⇒ Object

Registers new extension

Parameters:

  • extension (Class) —

    Extension class

  • options (Hash) —

    Optional extension options



332
333
334
 
# File 'lib/graphql/schema/resolver.rb', line 332

def extension(extension, **options)
  extensions << {extension => options}
end

.extensions ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



337
338
339
 
# File 'lib/graphql/schema/resolver.rb', line 337

def extensions
  @extensions ||= []
end

.extras(new_extras = nil) ⇒ Object

Additional info injected into #resolve

See Also:

  • {GraphQL{GraphQL::Schema{GraphQL::Schema::Field{GraphQL::Schema::Field#extras}


212
213
214
215
216
217
218
 
# File 'lib/graphql/schema/resolver.rb', line 212

def extras(new_extras = nil)
  if new_extras
    @own_extras = new_extras
  end
  own_extras = @own_extras || []
  own_extras + (superclass.respond_to?(:extras) ? superclass.extras : [])
end

.field_options ⇒ Object 



265
266
267
268
269
270
271
272
273
274
275
276
277
 
# File 'lib/graphql/schema/resolver.rb', line 265

def field_options
  {
    type: type_expr,
    description: description,
    extras: extras,
    resolver_method: :resolve_with_support,
    resolver_class: self,
    arguments: arguments,
    null: null,
    complexity: complexity,
    extensions: extensions,
  }
end

.null(allow_null = nil) ⇒ Object

Specifies whether or not the field is nullable. Defaults to true TODO unify with #type

Parameters:

  • allow_null (Boolean) (defaults to: nil) —

    Whether or not the response can be null



223
224
225
226
227
228
229
 
# File 'lib/graphql/schema/resolver.rb', line 223

def null(allow_null = nil)
  if !allow_null.nil?
    @null = allow_null
  end

  @null.nil? ? (superclass.respond_to?(:null) ? superclass.null : true) : @null
end

.resolve_method(new_method = nil) ⇒ Symbol

Default :resolve set below.

Returns:

  • (Symbol) —

    The method to call on instances of this object to resolve the field



203
204
205
206
207
208
 
# File 'lib/graphql/schema/resolver.rb', line 203

def resolve_method(new_method = nil)
  if new_method
    @resolve_method = new_method
  end
  @resolve_method || (superclass.respond_to?(:resolve_method) ? superclass.resolve_method : :resolve)
end

.type(new_type = nil, null: nil) ⇒ Class

Call this method to get the return type of the field, or use it as a configuration method to assign a return type instead of generating one. TODO unify with #null

Parameters:

  • new_type (Class, nil) (defaults to: nil) —

    If a type definition class is provided, it will be used as the return type of the field

  • null (true, false) —

    Whether or not the field may return nil

Returns:

  • (Class) —

    The type which this field returns.



238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
 
# File 'lib/graphql/schema/resolver.rb', line 238

def type(new_type = nil, null: nil)
  if new_type
    if null.nil?
      raise ArgumentError, "required argument `null:` is missing"
    end
    @type_expr = new_type
    @null = null
  else
    if @type_expr
      GraphQL::Schema::Member::BuildType.parse_type(@type_expr, null: @null)
    elsif superclass.respond_to?(:type)
      superclass.type
    else
      nil
    end
  end
end

.type_expr ⇒ Object

A non-normalized type configuration, without null applied



280
281
282
 
# File 'lib/graphql/schema/resolver.rb', line 280

def type_expr
  @type_expr || (superclass.respond_to?(:type_expr) ? superclass.type_expr : nil)
end

Instance Method Details

#authorized?(**inputs) ⇒ Boolean, early_return_data

Called after arguments are loaded, but before resolving.

Override it to check everything before calling the mutation.

Parameters:

  • inputs (Hash) —

    The input arguments

Returns:

  • (Boolean, early_return_data) —

    If false, execution will stop (and early_return_data will be returned instead, if present.)

Raises:



135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
 
# File 'lib/graphql/schema/resolver.rb', line 135

def authorized?(**inputs)
  self.class.arguments.each_value do |argument|
    arg_keyword = argument.keyword
    if inputs.key?(arg_keyword) && !(value = inputs[arg_keyword]).nil? && (value != argument.default_value)
      loads_type = @arguments_loads_as_type[arg_keyword]
      # If this argument resulted in an object being loaded,
      # then authorize this loaded object with its own policy.
      #
      # But if this argument was "just" a plain argument, like
      # a boolean, then authorize it based on the mutation.
      authorization_value = if loads_type
        value
      else
        self
      end

      arg_auth, err = argument.authorized?(authorization_value, context)
      if !arg_auth
        return arg_auth, err
      else
        true
      end
    else
      true
    end
  end
end

#ready?(**args) ⇒ Boolean, early_return_data

Called before arguments are prepared. Implement this hook to make checks before doing any work.

If it returns a lazy object (like a promise), it will be synced by GraphQL (but the resulting value won’t be used).

Parameters:

  • args (Hash) —

    The input arguments, if there are any

Returns:

  • (Boolean, early_return_data) —

    If false, execution will stop (and early_return_data will be returned instead, if present.)

Raises:



124
125
126
 
# File 'lib/graphql/schema/resolver.rb', line 124

def ready?(**args)
  true
end

#resolve(**args) ⇒ Object

Do the work. Everything happens here.

Returns:

  • (Object) —

    An object corresponding to the return type

Raises:



110
111
112
 
# File 'lib/graphql/schema/resolver.rb', line 110

def resolve(**args)
  raise GraphQL::RequiredImplementationMissingError, "#{self.class.name}#resolve should execute the field's logic"
end

#resolve_with_support(**args) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

This method is actually called by the runtime, it does some preparation and then eventually calls the user-defined #resolve method.



58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
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
102
103
104
105
106
 
# File 'lib/graphql/schema/resolver.rb', line 58

def resolve_with_support(**args)
  # First call the ready? hook which may raise
  ready_val = if args.any?
    ready?(**args)
  else
    ready?
  end
  context.schema.after_lazy(ready_val) do |is_ready, ready_early_return|
    if ready_early_return
      if is_ready != false
        raise "Unexpected result from #ready? (expected `true`, `false` or `[false, {...}]`): [#{authorized_result.inspect}, #{ready_early_return.inspect}]"
      else
        ready_early_return
      end
    elsif is_ready
      # Then call each prepare hook, which may return a different value
      # for that argument, or may return a lazy object
      load_arguments_val = load_arguments(args)
      context.schema.after_lazy(load_arguments_val) do |loaded_args|
        # Then call `authorized?`, which may raise or may return a lazy object
        authorized_val = if loaded_args.any?
          authorized?(loaded_args)
        else
          authorized?
        end
        context.schema.after_lazy(authorized_val) do |(authorized_result, early_return)|
          # If the `authorized?` returned two values, `false, early_return`,
          # then use the early return value instead of continuing
          if early_return
            if authorized_result == false
              early_return
            else
              raise "Unexpected result from #authorized? (expected `true`, `false` or `[false, {...}]`): [#{authorized_result.inspect}, #{early_return.inspect}]"
            end
          elsif authorized_result
            # Finally, all the hooks have passed, so resolve it
            if loaded_args.any?
              public_send(self.class.resolve_method, **loaded_args)
            else
              public_send(self.class.resolve_method)
            end
          else
            nil
          end
        end
      end
    end
  end
end