Class: GraphQL::Field

Inherits:
Object
  • Object
show all
Includes:
Define::InstanceDefinable
Defined in:
lib/graphql/field.rb,
lib/graphql/field/resolve.rb

Overview

Fields belong to ObjectTypes and InterfaceTypes.

They're usually created with the field helper. If you create it by hand, make sure #name is a String.

A field must have a return type, but if you want to defer the return type calculation until later, you can pass a proc for the return type. That proc will be called when the schema is defined.

For complex field definition, you can pass a block to the field helper, eg field :name do ... end. This block is equivalent to calling GraphQL::Field.define { ... }.

Resolve

Fields have resolve functions to determine their values at query-time. The default implementation is to call a method on the object based on the field name.

You can specify a custom proc with the resolve helper.

There are some shortcuts for common resolve implementations:

  • Provide property: to call a method with a different name than the field name
  • Provide hash_key: to resolve the field by doing a key lookup, eg obj[:my_hash_key]

Arguments

Fields can take inputs; they're called arguments. You can define them with the argument helper.

They can have default values which will be provided to resolve if the query doesn't include a value.

Only certain types maybe used for inputs:

  • Scalars
  • Enums
  • Input Objects
  • Lists of those types

Input types may also be non-null -- in that case, the query will fail if the input is not present.

Complexity

Fields can have complexity values which describe the computation cost of resolving the field. You can provide the complexity as a constant with complexity: or as a proc, with the complexity helper.

Examples:

Lazy type resolution

# If the field's type isn't defined yet, you can pass a proc
field :city, -> { TypeForModelName.find("City") }

Defining a field with a block

field :city, CityType do
  # field definition continues inside the block
end

Create a field which calls a method with the same name.

GraphQL::ObjectType.define do
  field :name, types.String, "The name of this thing "
end

Create a field that calls a different method on the object

GraphQL::ObjectType.define do
  # use the `property` keyword:
  field :firstName, types.String, property: :first_name
end

Create a field looks up with [hash_key]

GraphQL::ObjectType.define do
  # use the `hash_key` keyword:
  field :firstName, types.String, hash_key: :first_name
end

Create a field with an argument

field :students, types[StudentType] do
  argument :grade, types.Int
  resolve ->(obj, args, ctx) {
    Student.where(grade: args[:grade])
  }
end

Argument with a default value

field :events, types[EventType] do
  # by default, don't include past events
  argument :includePast, types.Boolean, default_value: false
  resolve ->(obj, args, ctx) {
    args[:includePast] # => false if no value was provided in the query
    # ...
  }
end

Custom complexity values

# Complexity can be a number or a proc.

# Complexity can be defined with a keyword:
field :expensive_calculation, !types.Int, complexity: 10

# Or inside the block:
field :expensive_calculation_2, !types.Int do
  complexity ->(ctx, args, child_complexity) { ctx[:current_user].staff? ? 0 : 10 }
end

Calculating the complexity of a list field

field :items, types[ItemType] do
  argument :limit, !types.Int
  # Mulitply the child complexity by the possible items on the list
  complexity ->(ctx, args, child_complexity) { child_complexity * args[:limit] }
end

Creating a field, then assigning it to a type

name_field = GraphQL::Field.define do
  name("Name")
  type(!types.String)
  description("The name of this thing")
  resolve ->(object, arguments, context) { object.name }
end

NamedType = GraphQL::ObjectType.define do
  # The second argument may be a GraphQL::Field
  field :name, name_field
end

Defined Under Namespace

Modules: DefaultLazyResolve, Resolve

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Define::InstanceDefinable

#define, #metadata, #redefine

Constructor Details

#initializeField

Returns a new instance of Field



206
207
208
209
210
211
212
213
214
215
# File 'lib/graphql/field.rb', line 206

def initialize
  @complexity = 1
  @arguments = {}
  @resolve_proc = build_default_resolver
  @lazy_resolve_proc = DefaultLazyResolve
  @relay_node_field = false
  @connection = false
  @connection_max_page_size = nil
  @edge_class = nil
end

Instance Attribute Details

#argumentsHash<String => GraphQL::Argument>

Returns Map String argument names to their Argument implementations

Returns:



165
166
167
# File 'lib/graphql/field.rb', line 165

def arguments
  @arguments
end

#arguments_classObject

Returns the value of attribute arguments_class



182
183
184
# File 'lib/graphql/field.rb', line 182

def arguments_class
  @arguments_class
end

#complexityNumeric, Proc

Returns The complexity for this field (default: 1), as a constant or a proc like ->(query_ctx, args, child_complexity) { } # Numeric

Returns:

  • (Numeric, Proc)

    The complexity for this field (default: 1), as a constant or a proc like ->(query_ctx, args, child_complexity) { } # Numeric



171
172
173
# File 'lib/graphql/field.rb', line 171

def complexity
  @complexity
end

#connection=(value) ⇒ Object (writeonly)

Sets the attribute connection

Parameters:

  • value

    the value to set the attribute connection to.



184
185
186
# File 'lib/graphql/field.rb', line 184

def connection=(value)
  @connection = value
end

#connection_max_page_sizenil, Integer

Returns:

  • (nil, Integer)


204
205
206
# File 'lib/graphql/field.rb', line 204

def connection_max_page_size
  @connection_max_page_size
end

#deprecation_reasonString?

Returns The client-facing reason why this field is deprecated (if present, the field is deprecated)

Returns:

  • (String, nil)

    The client-facing reason why this field is deprecated (if present, the field is deprecated)



162
163
164
# File 'lib/graphql/field.rb', line 162

def deprecation_reason
  @deprecation_reason
end

#descriptionString?

Returns The client-facing description of this field

Returns:

  • (String, nil)

    The client-facing description of this field



159
160
161
# File 'lib/graphql/field.rb', line 159

def description
  @description
end

#edge_classnil, Class

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.

Returns:

  • (nil, Class)


196
197
198
# File 'lib/graphql/field.rb', line 196

def edge_class
  @edge_class
end

#functionObject, GraphQL::Function

Returns The function used to derive this field

Returns:



180
181
182
# File 'lib/graphql/field.rb', line 180

def function
  @function
end

#hash_keyObject?

Returns The key to access with obj.[] to resolve this field (overrides #name if present)

Returns:

  • (Object, nil)

    The key to access with obj.[] to resolve this field (overrides #name if present)



177
178
179
# File 'lib/graphql/field.rb', line 177

def hash_key
  @hash_key
end

#lazy_resolve_proc<#call(obj, args, ctx)> (readonly)

Returns A proc-like object which can be called trigger a lazy resolution

Returns:

  • (<#call(obj, args, ctx)>)

    A proc-like object which can be called trigger a lazy resolution



153
154
155
# File 'lib/graphql/field.rb', line 153

def lazy_resolve_proc
  @lazy_resolve_proc
end

#mutationGraphQL::Relay::Mutation?

Returns The mutation this field was derived from, if it was derived from a mutation

Returns:



168
169
170
# File 'lib/graphql/field.rb', line 168

def mutation
  @mutation
end

#nameString

Returns The name of this field on its ObjectType (or InterfaceType)

Returns:



156
157
158
# File 'lib/graphql/field.rb', line 156

def name
  @name
end

#propertySymbol?

Returns The method to call on obj to return this field (overrides #name if present)

Returns:

  • (Symbol, nil)

    The method to call on obj to return this field (overrides #name if present)



174
175
176
# File 'lib/graphql/field.rb', line 174

def property
  @property
end

#relay_node_fieldBoolean

Returns True if this is the Relay find-by-id field

Returns:

  • (Boolean)

    True if this is the Relay find-by-id field



144
145
146
# File 'lib/graphql/field.rb', line 144

def relay_node_field
  @relay_node_field
end

#relay_nodes_fieldBoolean

Returns True if this is the Relay find-by-ids field

Returns:

  • (Boolean)

    True if this is the Relay find-by-ids field



147
148
149
# File 'lib/graphql/field.rb', line 147

def relay_nodes_field
  @relay_nodes_field
end

#resolve_proc<#call(obj, args, ctx)> (readonly)

Returns A proc-like object which can be called to return the field's value

Returns:

  • (<#call(obj, args, ctx)>)

    A proc-like object which can be called to return the field's value



150
151
152
# File 'lib/graphql/field.rb', line 150

def resolve_proc
  @resolve_proc
end

#subscription_scopenil, String

Returns Prefix for subscription names from this field

Returns:

  • (nil, String)

    Prefix for subscription names from this field



187
188
189
# File 'lib/graphql/field.rb', line 187

def subscription_scope
  @subscription_scope
end

Instance Method Details

#connection?Boolean

Returns:

  • (Boolean)


190
191
192
# File 'lib/graphql/field.rb', line 190

def connection?
  @connection
end

#edges?Boolean

Returns:

  • (Boolean)


199
200
201
# File 'lib/graphql/field.rb', line 199

def edges?
  !!@edge_class
end

#initialize_copy(other) ⇒ Object



217
218
219
220
# File 'lib/graphql/field.rb', line 217

def initialize_copy(other)
  super
  @arguments = other.arguments.dup
end

#lazy_resolve(obj, args, ctx) ⇒ Object

If #resolve returned and object which should be handled lazily, this method will be called later force the object to return its value.

Parameters:

Returns:

  • (Object)

    The result of calling the registered method on obj



283
284
285
# File 'lib/graphql/field.rb', line 283

def lazy_resolve(obj, args, ctx)
  @lazy_resolve_proc.call(obj, args, ctx)
end

#lazy_resolve=(new_lazy_resolve_proc) ⇒ Object

Assign a new resolve proc to this field. Used for #lazy_resolve



288
289
290
# File 'lib/graphql/field.rb', line 288

def lazy_resolve=(new_lazy_resolve_proc)
  @lazy_resolve_proc = new_lazy_resolve_proc
end

#prepare_lazy(obj, args, ctx) ⇒ GraphQL::Execution::Lazy

Prepare a lazy value for this field. It may be then-ed and resolved later.

Returns:



294
295
296
297
298
# File 'lib/graphql/field.rb', line 294

def prepare_lazy(obj, args, ctx)
  GraphQL::Execution::Lazy.new {
    lazy_resolve(obj, args, ctx)
  }
end

#resolve(object, arguments, context) ⇒ Object

Get a value for this field

Examples:

resolving a field value

field.resolve(obj, args, ctx)

Parameters:

  • object (Object)

    The object this field belongs to

  • arguments (Hash)

    Arguments declared in the query

  • context (GraphQL::Query::Context)


229
230
231
# File 'lib/graphql/field.rb', line 229

def resolve(object, arguments, context)
  resolve_proc.call(object, arguments, context)
end

#resolve=(new_resolve_proc) ⇒ Object

Provide a new callable for this field's resolve function. If nil, a new resolve proc will be build based on its #name, #property or #hash_key.

Parameters:

  • new_resolve_proc (<#call(obj, args, ctx)>, nil)


236
237
238
# File 'lib/graphql/field.rb', line 236

def resolve=(new_resolve_proc)
  @resolve_proc = new_resolve_proc || build_default_resolver
end

#to_sObject



273
274
275
# File 'lib/graphql/field.rb', line 273

def to_s
  "<Field name:#{name || "not-named"} desc:#{description} resolve:#{resolve_proc}>"
end

#typeObject

Get the return type for this field.



246
247
248
# File 'lib/graphql/field.rb', line 246

def type
  @clean_type ||= GraphQL::BaseType.resolve_related_type(@dirty_type)
end

#type=(new_return_type) ⇒ Object



240
241
242
243
# File 'lib/graphql/field.rb', line 240

def type=(new_return_type)
  @clean_type = nil
  @dirty_type = new_return_type
end