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_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)

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 class names -> connection_classes eg {"Array" => ArrayConnection}

{}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(nodes, arguments, field: nil, max_page_size: nil, parent: nil, context: nil) ⇒ BaseConnection

Make a connection, wrapping nodes

Parameters:

  • nodes (Object) —

    The collection of nodes

  • arguments (GraphQL::Query::Arguments) —

    Query arguments

  • field (GraphQL::Field) —

    The underlying field

  • max_page_size (Int) —

    The maximum number of results to return

  • parent (Object) —

    The object which this collection belongs to

  • context (GraphQL::Query::Context) —

    The context from the field being resolved



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# 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

Instance Attribute Details

#arguments ⇒ Object (readonly)

Returns the value of attribute arguments



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

def arguments
  @arguments
end

#context ⇒ Object (readonly)

Returns the value of attribute context



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

def context
  @context
end

#field ⇒ Object (readonly)

Returns the value of attribute field



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

def field
  @field
end

#max_page_size ⇒ Object (readonly)

Returns the value of attribute max_page_size



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

def max_page_size
  @max_page_size
end

#nodes ⇒ Object (readonly)

Returns the value of attribute nodes



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

def nodes
  @nodes
end

#parent ⇒ Object (readonly)

Returns the value of attribute parent



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

def parent
  @parent
end

Class Method Details

.connection_for_nodes(nodes) ⇒ subclass of BaseConnection

Find a connection implementation suitable for exposing nodes

Parameters:

  • nodes (Object) —

    A collection of nodes (eg, Array, AR::Relation)

Returns:

  • (subclass of BaseConnection) —

    a connection Class for wrapping nodes



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# 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

.register_connection_implementation(nodes_class, connection_class) ⇒ Object

Add connection_class as the connection wrapper for nodes_class eg, RelationConnection is the implementation for AR::Relation

Parameters:

  • nodes_class (Class) —

    A class representing a collection (eg, Array, AR::Relation)

  • connection_class (Class) —

    A class implementing Connection methods



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# 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

Instance Method Details

#after ⇒ String?

The value passed as after:, if there was one

Returns:

  • (String, nil) 


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# File 'lib/graphql/relay/base_connection.rb', line 85

def after
  arguments[:after]
end

#before ⇒ String?

The value passed as before:, if there was one

Returns:

  • (String, nil) 


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# File 'lib/graphql/relay/base_connection.rb', line 97

def before
  arguments[:before]
end

#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 141

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

#decode(data) ⇒ Object 



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# 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

#edge_nodes ⇒ Object

These are the nodes to render for this connection, probably wrapped by Edge



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# File 'lib/graphql/relay/base_connection.rb', line 103

def edge_nodes
  @edge_nodes ||= paged_nodes
end

#encode(data) ⇒ Object 



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# File 'lib/graphql/relay/base_connection.rb', line 67

def encode(data)
  @encoder.encode(data, nonce: true)
end

#end_cursor ⇒ Object

Used by pageInfo



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# 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

#first ⇒ Integer?

The value passed as first:, if there was one. Negative numbers become 0.

Returns:

  • (Integer, nil) 


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

def first
  @first ||= get_limited_arg(:first)
end

#has_next_page ⇒ Object

Used by pageInfo



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# File 'lib/graphql/relay/base_connection.rb', line 113

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 118

def has_previous_page
  !!(last && sliced_nodes.count > last)
end

#inspect ⇒ Object 



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# File 'lib/graphql/relay/base_connection.rb', line 145

def inspect
  "#<GraphQL::Relay::Connection @parent=#{@parent.inspect} @arguments=#{@arguments.to_h.inspect}>"
end

#last ⇒ Integer?

The value passed as last:, if there was one. Negative numbers become 0.

Returns:

  • (Integer, nil) 


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# File 'lib/graphql/relay/base_connection.rb', line 91

def last
  @last ||= get_limited_arg(:last)
end

#page_info ⇒ Object

Support the pageInfo field



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# File 'lib/graphql/relay/base_connection.rb', line 108

def page_info
  self
end

#start_cursor ⇒ Object

Used by pageInfo



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# 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