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

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 => ArrayConnection

{}
METHODS_FROM_ARGUMENTS =

Provide easy access to provided arguments:

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

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) ⇒ BaseConnection

Make a connection, wrapping nodes

Parameters:

  • The (Object)

    collection of nodes

  • Query

    arguments

  • field (Object)

    The underlying field

  • max_page_size (Int)

    The maximum number of results to return

  • parent (Object)

    The object which this collection belongs to


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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)
  @nodes = nodes
  @arguments = arguments
  @max_page_size = max_page_size
  @field = field
  @parent = parent
end

Instance Attribute Details

#argumentsObject (readonly)

Returns the value of attribute arguments


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# File 'lib/graphql/relay/base_connection.rb', line 49

def arguments
  @arguments
end

#fieldObject (readonly)

Returns the value of attribute field


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# File 'lib/graphql/relay/base_connection.rb', line 49

def field
  @field
end

#max_page_sizeObject (readonly)

Returns the value of attribute max_page_size


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# File 'lib/graphql/relay/base_connection.rb', line 49

def max_page_size
  @max_page_size
end

#nodesObject (readonly)

Returns the value of attribute nodes


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# File 'lib/graphql/relay/base_connection.rb', line 49

def nodes
  @nodes
end

#parentObject (readonly)

Returns the value of attribute parent


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# File 'lib/graphql/relay/base_connection.rb', line 49

def parent
  @parent
end

Class Method Details

.connection_for_nodes(nodes) ⇒ subclass of BaseConnection

Find a connection implementation suitable for exposing nodes

Parameters:

  • A (Object)

    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 26

def connection_for_nodes(nodes)
  # Check for class _names_ because classes can be redefined in Rails development
  ancestor_names = nodes.class.ancestors.map(&:name)
  implementation_class_name = ancestor_names.find do |ancestor_class_name|
    CONNECTION_IMPLEMENTATIONS.include? ancestor_class_name
  end

  if implementation_class_name.nil?
    raise("No connection implementation to wrap #{nodes.class} (#{nodes})")
  else
    CONNECTION_IMPLEMENTATIONS[implementation_class_name]
  end
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:

  • A (Class)

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

  • A (Class)

    class implementing Connection methods


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# File 'lib/graphql/relay/base_connection.rb', line 44

def register_connection_implementation(nodes_class, connection_class)
  CONNECTION_IMPLEMENTATIONS[nodes_class.name] = connection_class
end

Instance Method Details

#afterObject

The value passed as after:, if there was one


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# File 'lib/graphql/relay/base_connection.rb', line 76

METHODS_FROM_ARGUMENTS.each do |arg_name|
  define_method(arg_name) do
    arguments[arg_name]
  end
end

#beforeObject

The value passed as before:, if there was one


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# File 'lib/graphql/relay/base_connection.rb', line 76

METHODS_FROM_ARGUMENTS.each do |arg_name|
  define_method(arg_name) do
    arguments[arg_name]
  end
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 122

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

#edge_nodesObject

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 84

def edge_nodes
  @edge_nodes ||= paged_nodes
end

#end_cursorObject

Used by pageInfo


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

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

#firstObject

The value passed as first:, if there was one


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# File 'lib/graphql/relay/base_connection.rb', line 76

METHODS_FROM_ARGUMENTS.each do |arg_name|
  define_method(arg_name) do
    arguments[arg_name]
  end
end

#has_next_pageObject

Used by pageInfo


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# File 'lib/graphql/relay/base_connection.rb', line 94

def has_next_page
  !!(first && sliced_nodes.count > first)
end

#has_previous_pageObject

Used by pageInfo


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# File 'lib/graphql/relay/base_connection.rb', line 99

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

#lastObject

The value passed as last:, if there was one


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# File 'lib/graphql/relay/base_connection.rb', line 76

METHODS_FROM_ARGUMENTS.each do |arg_name|
  define_method(arg_name) do
    arguments[arg_name]
  end
end

#page_infoObject

Support the pageInfo field


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

def page_info
  self
end

#start_cursorObject

Used by pageInfo


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# File 'lib/graphql/relay/base_connection.rb', line 104

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