Class: GraphQL::Pagination::Connection

Inherits:
Object
  • Object
show all
Defined in:
lib/graphql/pagination/connection.rb

Overview

A Connection wraps a list of items and provides cursor-based pagination over it.

Connections were introduced by Facebook’s Relay front-end framework, but proved to be generally useful for GraphQL APIs. When in doubt, use connections to serve lists (like Arrays, ActiveRecord::Relations) via GraphQL.

Unlike the previous connection implementation, these default to bidirectional pagination.

Pagination arguments and context may be provided at initialization or assigned later (see Schema::Field::ConnectionExtension).

Direct Known Subclasses

ArrayConnection, RelationConnection

Defined Under Namespace

Classes: Edge, PaginationImplementationMissingError

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(items, parent: nil, field: nil, context: nil, first: nil, after: nil, max_page_size: :not_given, default_page_size: :not_given, last: nil, before: nil, edge_class: nil, arguments: nil) ⇒ Connection

Returns a new instance of Connection.

Parameters:

  • items (Object) —

    some unpaginated collection item, like an Array or ActiveRecord::Relation

  • context (Query::Context) (defaults to: nil)
  • parent (Object) (defaults to: nil) —

    The object this collection belongs to

  • first (Integer, nil) (defaults to: nil) —

    The limit parameter from the client, if it provided one

  • after (String, nil) (defaults to: nil) —

    A cursor for pagination, if the client provided one

  • last (Integer, nil) (defaults to: nil) —

    Limit parameter from the client, if provided

  • before (String, nil) (defaults to: nil) —

    A cursor for pagination, if the client provided one.

  • arguments (Hash) (defaults to: nil) —

    The arguments to the field that returned the collection wrapped by this connection

  • max_page_size (Integer, nil) (defaults to: :not_given) —

    A configured value to cap the result size. Applied as first if neither first or last are given and no default_page_size is set.

  • default_page_size (Integer, nil) (defaults to: :not_given) —

    A configured value to determine the result size when neither first or last are given.



61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
 
# File 'lib/graphql/pagination/connection.rb', line 61

def initialize(items, parent: nil, field: nil, context: nil, first: nil, after: nil, max_page_size: :not_given, default_page_size: :not_given, last: nil, before: nil, edge_class: nil, arguments: nil)
  @items = items
  @parent = parent
  @context = context
  @field = field
  @first_value = first
  @after_value = after
  @last_value = last
  @before_value = before
  @arguments = arguments
  @edge_class = edge_class || self.class::Edge
  # This is only true if the object was _initialized_ with an override
  # or if one is assigned later.
  @has_max_page_size_override = max_page_size != :not_given
  @max_page_size = if max_page_size == :not_given
    nil
  else
    max_page_size
  end
  @has_default_page_size_override = default_page_size != :not_given
  @default_page_size = if default_page_size == :not_given
    nil
  else
    default_page_size
  end
end

Instance Attribute Details

#after_value ⇒ Object

Raw access to client-provided values. (max_page_size not applied to first or last.)



28
29
30
 
# File 'lib/graphql/pagination/connection.rb', line 28

def after_value
  @after_value
end

#arguments ⇒ Hash<Symbol => Object>

Returns The field arguments from the field that returned this connection.

Returns:

  • (Hash<Symbol => Object>) —

    The field arguments from the field that returned this connection



49
50
51
 
# File 'lib/graphql/pagination/connection.rb', line 49

def arguments
  @arguments
end

#before_value ⇒ Object

Raw access to client-provided values. (max_page_size not applied to first or last.)



28
29
30
 
# File 'lib/graphql/pagination/connection.rb', line 28

def before_value
  @before_value
end

#context ⇒ GraphQL::Query::Context

Returns:



22
23
24
 
# File 'lib/graphql/pagination/connection.rb', line 22

def context
  @context
end

#edge_class ⇒ Class

Returns A wrapper class for edges of this connection.

Returns:

  • (Class) —

    A wrapper class for edges of this connection



161
162
163
 
# File 'lib/graphql/pagination/connection.rb', line 161

def edge_class
  @edge_class
end

#field ⇒ GraphQL::Schema::Field

Returns The field this connection was returned by.

Returns:



164
165
166
 
# File 'lib/graphql/pagination/connection.rb', line 164

def field
  @field
end

#first ⇒ Integer?

Returns A clamped first value. (The underlying instance variable doesn’t have limits on it.) If neither first nor last is given, but default_page_size is present, default_page_size is used for first. If default_page_size is greater than max_page_size, it'll be clamped down to max_page_size. If default_page_size is nil, use max_page_size`.

Returns:

  • (Integer, nil) —

    A clamped first value. (The underlying instance variable doesn’t have limits on it.) If neither first nor last is given, but default_page_size is present, default_page_size is used for first. If default_page_size is greater than max_page_size, it'll be clamped down to max_page_size. If default_page_size is nil, use max_page_size`.



130
131
132
133
134
135
136
137
138
 
# File 'lib/graphql/pagination/connection.rb', line 130

def first
  @first ||= begin
    capped = limit_pagination_argument(@first_value, max_page_size)
    if capped.nil? && last.nil?
      capped = limit_pagination_argument(default_page_size, max_page_size) || max_page_size
    end
    capped
  end
end

#first_value ⇒ Object

Raw access to client-provided values. (max_page_size not applied to first or last.)



28
29
30
 
# File 'lib/graphql/pagination/connection.rb', line 28

def first_value
  @first_value
end

#items ⇒ Object (readonly)

Returns A list object, from the application. This is the unpaginated value passed into the connection.

Returns:

  • (Object) —

    A list object, from the application. This is the unpaginated value passed into the connection.



19
20
21
 
# File 'lib/graphql/pagination/connection.rb', line 19

def items
  @items
end

#last ⇒ Integer?

Returns A clamped last value. (The underlying instance variable doesn’t have limits on it).

Returns:

  • (Integer, nil) —

    A clamped last value. (The underlying instance variable doesn’t have limits on it)



151
152
153
 
# File 'lib/graphql/pagination/connection.rb', line 151

def last
  @last ||= limit_pagination_argument(@last_value, max_page_size)
end

#last_value ⇒ Object

Raw access to client-provided values. (max_page_size not applied to first or last.)



28
29
30
 
# File 'lib/graphql/pagination/connection.rb', line 28

def last_value
  @last_value
end

#parent ⇒ Object

Returns the object this collection belongs to.

Returns:

  • (Object) —

    the object this collection belongs to



25
26
27
 
# File 'lib/graphql/pagination/connection.rb', line 25

def parent
  @parent
end

Instance Method Details

#after ⇒ String?

Returns the client-provided cursor. "" is treated as nil.

Returns:

  • (String, nil) —

    the client-provided cursor. "" is treated as nil.



40
41
42
43
44
45
46
 
# File 'lib/graphql/pagination/connection.rb', line 40

def after
  if defined?(@after)
    @after
  else
    @after = @after_value == "" ? nil : @after_value
  end
end

#before ⇒ String?

Returns the client-provided cursor. "" is treated as nil.

Returns:

  • (String, nil) —

    the client-provided cursor. "" is treated as nil.



31
32
33
34
35
36
37
 
# File 'lib/graphql/pagination/connection.rb', line 31

def before
  if defined?(@before)
    @before
  else
    @before = @before_value == "" ? nil : @before_value
  end
end

#cursor_for(item) ⇒ String

Return a cursor for this item.

Parameters:

  • item (Object) —

    one of the passed in #items, taken from #nodes

Returns:

  • (String)

Raises:



205
206
207
 
# File 'lib/graphql/pagination/connection.rb', line 205

def cursor_for(item)
  raise PaginationImplementationMissingError, "Implement #{self.class}#cursor_for(item) to return the cursor for #{item.inspect}"
end

#default_page_size ⇒ Object 



110
111
112
113
114
115
116
 
# File 'lib/graphql/pagination/connection.rb', line 110

def default_page_size
  if @has_default_page_size_override
    @default_page_size
  else
    context.schema.default_page_size
  end
end

#default_page_size=(new_value) ⇒ Object 



105
106
107
108
 
# File 'lib/graphql/pagination/connection.rb', line 105

def default_page_size=(new_value)
  @has_default_page_size_override = true
  @default_page_size = new_value
end

#edge_nodes ⇒ Object

Deprecated.

use #nodes instead

A dynamic alias for compatibility with Relay::BaseConnection.



173
174
175
 
# File 'lib/graphql/pagination/connection.rb', line 173

def edge_nodes
  nodes
end

#edges ⇒ Array<Edge>

Returns #nodes, but wrapped with Edge instances.

Returns:

  • (Array<Edge>) —

    #nodes, but wrapped with Edge instances



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

def edges
  @edges ||= nodes.map { |n| @edge_class.new(n, self) }
end

#end_cursor ⇒ String

Returns The cursor of the last item in #nodes.

Returns:

  • (String) —

    The cursor of the last item in #nodes



198
199
200
 
# File 'lib/graphql/pagination/connection.rb', line 198

def end_cursor
  nodes.last && cursor_for(nodes.last)
end

#has_default_page_size_override? ⇒ Boolean

Returns:

  • (Boolean) 


118
119
120
 
# File 'lib/graphql/pagination/connection.rb', line 118

def has_default_page_size_override?
  @has_default_page_size_override
end

#has_max_page_size_override? ⇒ Boolean

Returns:

  • (Boolean) 


101
102
103
 
# File 'lib/graphql/pagination/connection.rb', line 101

def has_max_page_size_override?
  @has_max_page_size_override
end

#has_next_page ⇒ Boolean

Returns True if there are more items after this page.

Returns:

  • (Boolean) —

    True if there are more items after this page

Raises:



183
184
185
 
# File 'lib/graphql/pagination/connection.rb', line 183

def has_next_page
  raise PaginationImplementationMissingError, "Implement #{self.class}#has_next_page to return the next-page check"
end

#has_previous_page ⇒ Boolean

Returns True if there were items before these items.

Returns:

  • (Boolean) —

    True if there were items before these items

Raises:



188
189
190
 
# File 'lib/graphql/pagination/connection.rb', line 188

def has_previous_page
  raise PaginationImplementationMissingError, "Implement #{self.class}#has_previous_page to return the previous-page check"
end

#max_page_size ⇒ Object 



93
94
95
96
97
98
99
 
# File 'lib/graphql/pagination/connection.rb', line 93

def max_page_size
  if @has_max_page_size_override
    @max_page_size
  else
    context.schema.default_max_page_size
  end
end

#max_page_size=(new_value) ⇒ Object 



88
89
90
91
 
# File 'lib/graphql/pagination/connection.rb', line 88

def max_page_size=(new_value)
  @has_max_page_size_override = true
  @max_page_size = new_value
end

#nodes ⇒ Array<Object>

Returns A slice of #items, constrained by @first_value/@after_value/@last_value/@before_value.

Returns:

  • (Array<Object>) —

    A slice of #items, constrained by @first_value/@after_value/@last_value/@before_value

Raises:



167
168
169
 
# File 'lib/graphql/pagination/connection.rb', line 167

def nodes
  raise PaginationImplementationMissingError, "Implement #{self.class}#nodes to paginate `@items`"
end

#page_info ⇒ Object

The connection object itself implements PageInfo fields



178
179
180
 
# File 'lib/graphql/pagination/connection.rb', line 178

def page_info
  self
end

#range_add_edge(item) ⇒ Edge

This is called by Relay::RangeAdd – it can be overridden when item needs some modifications based on this connection’s state.

Parameters:

  • item (Object) —

    An item newly added to items

Returns:



145
146
147
 
# File 'lib/graphql/pagination/connection.rb', line 145

def range_add_edge(item)
  edge_class.new(item, self)
end

#start_cursor ⇒ String

Returns The cursor of the first item in #nodes.

Returns:

  • (String) —

    The cursor of the first item in #nodes



193
194
195
 
# File 'lib/graphql/pagination/connection.rb', line 193

def start_cursor
  nodes.first && cursor_for(nodes.first)
end