Class: GraphQL::Relay::BaseConnection

Inherits:
Object
  • Object
show all
Defined in:
lib/graphql/relay/base_connection.rb

Overview

Subclasses must implement:

- {#cursor_from_node}, which returns an opaque cursor for the given item
- {#sliced_edges}, which slices by `before` & `after`
- {#paged_edges}, which applies `first` & `last` limits

In a subclass, you have access to

- {#object}, the object which the connection will wrap
- {#first}, {#after}, {#last}, {#before} (arguments passed to the field)

Direct Known Subclasses

ArrayConnection, RelationConnection

Constant Summary collapse

CURSOR_SEPARATOR =

Just to encode data in the cursor, use something that won’t conflict

"---"
CONNECTION_IMPLEMENTATIONS =

Map of collection classes -> connection_classes eg Array -> ArrayConnection

{}
METHODS_FROM_ARGUMENTS =

Provide easy access to provided arguments:

[:first, :after, :last, :before, :order]

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(object, arguments) ⇒ BaseConnection

Returns a new instance of BaseConnection.



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# File 'lib/graphql/relay/base_connection.rb', line 54

def initialize(object, arguments)
  @object = object
  @arguments = arguments
end

Instance Attribute Details

#arguments ⇒ Object (readonly)

Returns the value of attribute arguments.



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# File 'lib/graphql/relay/base_connection.rb', line 52

def arguments
  @arguments
end

#object ⇒ Object (readonly)

Returns the value of attribute object.



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# File 'lib/graphql/relay/base_connection.rb', line 52

def object
  @object
end

Class Method Details

.connection_for_items(items) ⇒ subclass of BaseConnection

Returns a connection wrapping ‘items`.

Returns:



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# File 'lib/graphql/relay/base_connection.rb', line 35

def self.connection_for_items(items)
  implementation = CONNECTION_IMPLEMENTATIONS.find do |items_class, connection_class|
    items.is_a?(items_class)
  end
  if implementation.nil?
    raise("No connection implementation to wrap #{items.class}")
  else
    implementation[1]
  end
end

.create_type(wrapped_type, &block) ⇒ Object

Create a connection which exposes edges of this type



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# File 'lib/graphql/relay/base_connection.rb', line 21

def self.create_type(wrapped_type, &block)
  edge_type = Edge.create_type(wrapped_type)

  connection_type = ObjectType.define do
    name("#{wrapped_type.name}Connection")
    field :edges, types[edge_type]
    field :pageInfo, PageInfo, property: :page_info
    block && instance_eval(&block)
  end

  connection_type
end

.register_connection_implementation(items_class, connection_class) ⇒ Object

Add ‘connection_class` as the connection wrapper for `items_class` eg, `RelationConnection` is the implementation for `AR::Relation`



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# File 'lib/graphql/relay/base_connection.rb', line 48

def self.register_connection_implementation(items_class, connection_class)
  CONNECTION_IMPLEMENTATIONS[items_class] = connection_class
end

Instance Method Details

#cursor_from_node(object) ⇒ Object

An opaque operation which returns a connection-specific cursor.

Raises:

  • (NotImplementedError) 


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# File 'lib/graphql/relay/base_connection.rb', line 89

def cursor_from_node(object)
  raise NotImplementedError, "must return a cursor for this object/connection pair"
end

#edges ⇒ Object

Wrap nodes in Edges so they expose cursors.



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# File 'lib/graphql/relay/base_connection.rb', line 69

def edges
  @edges ||= paged_nodes.map { |item| Edge.new(item, self) }
end

#has_next_page ⇒ Object

Used by ‘pageInfo`



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# File 'lib/graphql/relay/base_connection.rb', line 79

def has_next_page
  first && sliced_nodes.count > first
end

#has_previous_page ⇒ Object

Used by ‘pageInfo`



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# File 'lib/graphql/relay/base_connection.rb', line 84

def has_previous_page
  last && sliced_nodes.count > last
end

#page_info ⇒ Object

Support the ‘pageInfo` field



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# File 'lib/graphql/relay/base_connection.rb', line 74

def page_info
  self
end