graphql-rubyのカーソルを作っているながれ

cursor.tour

{
  "$schema": "https://aka.ms/codetour-schema",
  "title": "カーソルがどうやって作られているか",
  "steps": [
    {
      "file": "lib/graphql/types/relay/page_info.rb",
      "description": "pageinfoの定義から見ていく\n",
      "line": 6
    },
    {
      "file": "lib/graphql/types/relay/page_info.rb",
      "description": "PageInfoBehaviorsをincludeしている",
      "line": 7
    },
    {
      "file": "lib/graphql/types/relay/page_info_behaviors.rb",
      "description": "end_cursor はここ\n",
      "line": 18
    },
    {
      "file": "lib/graphql/types/relay/page_info_behaviors.rb",
      "description": "includedされた時にこのメソッドが呼び出される\n\nhttps://docs.ruby-lang.org/ja/latest/method/Module/i/included.html\n",
      "line": 6
    },
    {
      "file": "lib/graphql/types/relay/page_info_behaviors.rb",
      "description": "child_class のメソッドにClassMethodsを追加している\n\nつまり今回は default_relay?がPageInfoクラスに追加される\n（今後ClassMethodsが増えても記述量が増えなくて便利、的な？）\n",
      "line": 7
    },
    {
      "file": "lib/graphql/types/relay/page_info_behaviors.rb",
      "description": "pageInfoにhas_next_pageメソッドを追加している",
      "line": 9
    },
    {
      "file": "lib/graphql/types/relay/page_info_behaviors.rb",
      "description": "pageInfoにend_cursorメソッドを追加している",
      "line": 18
    },
    {
      "file": "lib/graphql/pagination/connection.rb",
      "description": "end_cursorの実装はここ",
      "line": 214
    },
    {
      "file": "lib/graphql/pagination/connection.rb",
      "description": "end_cursorの実装はここ",
      "line": 214
    },
    {
      "file": "lib/graphql/pagination/connection.rb",
      "description": "nodes.lastがある場合（つまりnodeがなかった場合はnulが返ってくる）\ncursor_for(nodes.last)の値が返ってくる\n\n",
      "line": 215
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "nodes.index(item) + 1\nindexは Array#index のindex。つまりnodeの中でitemが何番目の要素かを返す。0始まりなので+1してる",
      "line": 50
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "@paged_nodes_offset はここで入れてる\n\nrelation_offsetとは",
      "line": 210
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "初期代入はここっぽい　\n@sliced_nodes_offsetとは",
      "line": 188
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "sliced_nodes_offsetの代入場所\n\nnext_offsetとは",
      "line": 141
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "next_offsetの代入場所\n\nrelation_offsetとは",
      "line": 119
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "itemsの型によるっぽい",
      "line": 66
    },
    {
      "file": "lib/graphql/pagination/active_record_relation_connection.rb",
      "description": "ここでrelation_offsetを定義してる",
      "line": 35
    },
    {
      "file": "lib/graphql/pagination/active_record_relation_connection.rb",
      "description": "relation.class は User::ActiveRecord_Relation\n\noffset_valueの定義場所\n\n04:0> m = relation.method(:offset_value)\n05:0> m.source_location\n=> \n[\"/Users/yana/.rbenv/versions/3.1.1/lib/ruby/gems/3.1.0/gems/activerecord-6.1.6.1/lib/active_record/relation/query_methods.rb\",                  , 98]",
      "line": 40
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "難しくなったのでもう一度ここに帰る\n\n(relation対象のnodesのindex + 1) + nodes_offsetのpaged？ -\n\nusers(first:1, after:\"Mg\")（Mgは2番目の要素）\nの計算式は 1 + 2 - 0 だった\n\npaged_nodes_offset は afterより前のnodeの数と考えていいのかな",
      "line": 51
    },
    {
      "file": "lib/graphql/pagination/connection.rb",
      "description": "ここでは定義されていないので継承先で実装されていそう",
      "line": 222
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "nodesはload_nodesした後の@nodesの値",
      "line": 50
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "ActiveRecordRelationはRelationConnectionを継承しているので、cursor_forの実装はここ",
      "line": 47
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "```ruby\n08:0> limited_nodes.to_a\n=> \n[#<User:0x0000000114997f18                                                   \n  id: 3,                                                                     \n  name: \"user\",                                                              \n  email: nil,                                                                \n  created_at: Mon, 18 Jul 2022 09:49:16.616049000 UTC +00:00,                \n  updated_at: Mon, 18 Jul 2022 09:49:16.616049000 UTC +00:00>]               \nirb(#<GraphQL::Pagination::ActiveRecordRelationConnection:0x0000000114dae930>):0\n\n```\nlimited_nodes自体はUser::ActiveRecord_Relation",
      "line": 222
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "pagenationで指定された対象のnodesを @nodes 格納していた",
      "line": 48
    },
    {
      "file": "lib/graphql/pagination/relation_connection.rb",
      "description": "load_nodesは何をしているか",
      "line": 48
    }
  ],
  "ref": "master"
}