class GraphQL::Relay::BaseConnection
Subclasses must implement:
- {#cursor_from_node}, which returns an opaque cursor for the given item - {#sliced_nodes}, which slices by `before` & `after` - {#paged_nodes}, which applies `first` & `last` limits
In a subclass, you have access to
- {#nodes}, the collection which the connection will wrap - {#first}, {#after}, {#last}, {#before} (arguments passed to the field) - {#max_page_size} (the specified maximum page size that can be returned from a connection)
Constants
- CONNECTION_IMPLEMENTATIONS
Map of collection class names -> connection_classes eg `{“Array” => ArrayConnection}`
- CURSOR_SEPARATOR
Just to encode data in the cursor, use something that won't conflict
Attributes
Public Class Methods
Find a connection implementation suitable for exposing `nodes`
@param nodes [Object] A collection of nodes (eg, Array, AR::Relation) @return [subclass of BaseConnection] a connection Class for wrapping `nodes`
# File lib/graphql/relay/base_connection.rb, line 27 def connection_for_nodes(nodes) # Check for class _names_ because classes can be redefined in Rails development nodes.class.ancestors.each do |ancestor| conn_impl = CONNECTION_IMPLEMENTATIONS[ancestor.name] if conn_impl return conn_impl end end # Should have found a connection during the loop: raise("No connection implementation to wrap #{nodes.class} (#{nodes})") end
Make a connection, wrapping `nodes` @param nodes [Object] The collection of nodes @param arguments [GraphQL::Query::Arguments] Query
arguments @param field [GraphQL::Field] The underlying field @param max_page_size
[Int] The maximum number of results to return @param parent [Object] The object which this collection belongs to @param context [GraphQL::Query::Context] The context from the field being resolved
# File lib/graphql/relay/base_connection.rb, line 57 def initialize(nodes, arguments, field: nil, max_page_size: nil, parent: nil, context: nil) @context = context @nodes = nodes @arguments = arguments @field = field @parent = parent @encoder = context ? @context.schema.cursor_encoder : GraphQL::Schema::Base64Encoder @max_page_size = max_page_size.nil? && context ? @context.schema.default_max_page_size : max_page_size end
Add `connection_class` as the connection wrapper for `nodes_class` eg, `RelationConnection` is the implementation for `AR::Relation` @param nodes_class [Class] A class representing a collection (eg, Array, AR::Relation) @param connection_class [Class] A class implementing Connection methods
# File lib/graphql/relay/base_connection.rb, line 43 def register_connection_implementation(nodes_class, connection_class) CONNECTION_IMPLEMENTATIONS[nodes_class.name] = connection_class end
Public Instance Methods
The value passed as `after:`, if there was one @return [String, nil]
# File lib/graphql/relay/base_connection.rb, line 85 def after arguments[:after] end
The value passed as `before:`, if there was one @return [String, nil]
# File lib/graphql/relay/base_connection.rb, line 97 def before arguments[:before] end
An opaque operation which returns a connection-specific cursor.
# File lib/graphql/relay/base_connection.rb, line 141 def cursor_from_node(object) raise NotImplementedError, "must return a cursor for this object/connection pair" end
# File lib/graphql/relay/base_connection.rb, line 71 def decode(data) @encoder.decode(data, nonce: true) rescue ArgumentError raise GraphQL::ExecutionError, "Invalid cursor: #{data.inspect}" end
These are the nodes to render for this connection, probably wrapped by {GraphQL::Relay::Edge}
# File lib/graphql/relay/base_connection.rb, line 103 def edge_nodes @edge_nodes ||= paged_nodes end
# File lib/graphql/relay/base_connection.rb, line 67 def encode(data) @encoder.encode(data, nonce: true) end
Used by `pageInfo`
# File lib/graphql/relay/base_connection.rb, line 132 def end_cursor if end_node = (respond_to?(:paged_nodes_array, true) ? paged_nodes_array : paged_nodes).last return cursor_from_node(end_node) else return nil end end
The value passed as `first:`, if there was one. Negative numbers become `0`. @return [Integer, nil]
# File lib/graphql/relay/base_connection.rb, line 79 def first @first ||= get_limited_arg(:first) end
Used by `pageInfo`
# File lib/graphql/relay/base_connection.rb, line 113 def has_next_page !!(first && sliced_nodes.count > first) end
Used by `pageInfo`
# File lib/graphql/relay/base_connection.rb, line 118 def has_previous_page !!(last && sliced_nodes.count > last) end
# File lib/graphql/relay/base_connection.rb, line 145 def inspect "#<GraphQL::Relay::Connection @parent=#{@parent.inspect} @arguments=#{@arguments.to_h.inspect}>" end
The value passed as `last:`, if there was one. Negative numbers become `0`. @return [Integer, nil]
# File lib/graphql/relay/base_connection.rb, line 91 def last @last ||= get_limited_arg(:last) end
Support the `pageInfo` field
# File lib/graphql/relay/base_connection.rb, line 108 def page_info self end
Used by `pageInfo`
# File lib/graphql/relay/base_connection.rb, line 123 def start_cursor if start_node = (respond_to?(:paged_nodes_array, true) ? paged_nodes_array : paged_nodes).first return cursor_from_node(start_node) else return nil end end
Private Instance Methods
Return a sanitized `arguments` (don't allow negatives)
# File lib/graphql/relay/base_connection.rb, line 152 def get_limited_arg(arg_name) arg_value = arguments[arg_name] if arg_value.nil? arg_value elsif arg_value < 0 0 else arg_value end end
# File lib/graphql/relay/base_connection.rb, line 163 def paged_nodes raise NotImplementedError, "must return nodes for this connection after paging" end
# File lib/graphql/relay/base_connection.rb, line 167 def sliced_nodes raise NotImplementedError, "must return all nodes for this connection after chopping off first and last" end