Dart - Database(indexedDB(2つのブジェクトストアからデータを収集, 絞り込み))

Dart: Up and Running
(O'Reilly Media)
Kathy Walrath Seth Ladd (著)
[Kindle版]
このブログでの感想

開発環境

• OS X Mavericks - Apple (OS)
• Dart Editor (開発環境)
• Dartium | Dart/ Structured web apps (ブラウザ, Dart VM 用 (Chromium with the Dart VM))
• Safari (ブラウザ, JavaScript 用)
• Dart (プログラミング言語)

初めてのコンピュータサイエンス(Jennifer Campbell、Paul Gries、Jason Montojo、Greg Wilson(著)長尾 高弘(翻訳))の15章(データベース)、15.11(練習問題)、2-c.をDartで解いてみる。

その他参考書籍

• What is Dart? [Kindle版] (O'Reilly Media) Kathy Walrath Seth Ladd (著) このブログでの感想

15.11(練習問題)、2-c.

コード

sample.dart

import 'dart:html';
import 'dart:indexed_db' as idb;
import 'dart:async' as async;

void main() {
  run.onClick.listen((MouseEvent event){
    pre.text = window.navigator.userAgent + '\n';
    if(idb.IdbFactory.supported){
      states.clear();
      areas.clear();
      window.indexedDB.open('census.db',
          version: 3,
          onUpgradeNeeded: _initializeDatabase)
      .then(_loadFromDB)
      .then(_show);
    } else {
      pre.text += 'このブラウザではindexedDBは使用出来ません';
    }
  });
  clear.onClick.listen((MouseEvent event) => pre.text = '');
}

ButtonElement run= querySelector('#run_dart');
ButtonElement clear = querySelector('#clear');
PreElement pre = querySelector('#pre0');
List areas = [];
List states = [];
async.Future _loadFromDB(idb.Database db){
  var transaction = db.transaction('Capitals', 'readwrite');
  var object_store = transaction.objectStore('Capitals');
  var key = object_store.keyPath;
  var cursors = object_store.openCursor(autoAdvance: true).asBroadcastStream();
  cursors.listen((var cursor) {
    var value = cursor.value;
    if(value['Population'] > 100000){
      states.add(value[key]);
    }
  });
  transaction = db.transaction('Density', 'readwrite');
  object_store = transaction.objectStore('Density');
  key = object_store.keyPath;
  cursors = object_store.openCursor(autoAdvance: true).asBroadcastStream();
  cursors.listen((var cursor) {
    var value = cursor.value;
    if(states.contains(value[key])){
      areas.add(value['Area']);
      states.remove(value[key]);
    }
  });
  return transaction.completed;
}

void _initializeDatabase(idb.VersionChangeEvent e) {
  idb.Database db = (e.target as idb.Request).result;
  var object_store = db.createObjectStore('Capitals',
      keyPath:'State',
      autoIncrement: true);
}

async.Future _show(idb.Database db){
  for(var area in areas){
    pre.text += '$area\n';
  }
  pre.text += '終了\n';
}