Dart - クラスの作成(constructorとオプション引数(角括弧「[]」))

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)

Head First JavaScript ―頭とからだで覚えるJavaScriptの基本( Michael Morrison (著), 豊福 剛 (翻訳)、オライリージャパン)の10章(カスタムオブジェクトを作成する)、自分で考えてみよう(p.477-479)をDartで考えてみる。

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

自分で考えてみよう(p.477-479)

コード

sample.dart

import 'dart:html';

void main () {
  run.onClick.listen((MouseEvent event) => Blog.showBlog());
  clear.onClick.listen((MouseEvent event) => div.innerHtml = '');
}

ButtonElement run = querySelector('#run_dart');
ButtonElement clear = querySelector('#clear');
DivElement div = querySelector('#d0');

List<zBlog> blog = [new Blog(null, null,
    'https://lh5.googleusercontent.com/' +
    'rljVgO2PsdWyf5TVbjD3xefkzEDGpXR5QVeAKaPnJlI=s222-p-no'),
                   new Blog(new DateTime(2008, 8, 14), '注文していた…'),
                   new Blog(new DateTime(2008, 8, 19), '新しいキューブは…'),
                   new Blog(new DateTime(2008, 8, 16), '新しいキューブと…'),
                   new Blog(new DateTime(2008, 8, 21), 'ネットで…')];

String shortFormat(DateTime dt){
  return '${dt.month}/${dt.day}/${dt.year}';
}

class Blog implements Comparable{
  static const SIGNATURE = 'This blog created by Puzzler Ruby';
  static void showBlog([int n]) {
      var blog_html = '';
      if (n == null){
        n = blog.length;
      }
      blog.sort((x, y) => x.compareTo(y));
      bool highlight = true;
      blog.forEach((Blog entry){
        div.append(entry.toHtml(highlight));
        highlight = !highlight;
      });
  }
  DateTime date_time;
  String body;
  String image;
  Blog([DateTime date_time, String body, String image]){
    print('$date_time, $body, $image');
    this.date_time = date_time != null ? date_time : new DateTime.now();
    this.body = body != null ? body : 'Nothing going on today';
    this.image = image;
  }
  ParagraphElement toHtml(bool highlight){
    ParagraphElement p = new ParagraphElement();
    p.appendHtml('<zstrong>${shortFormat(date_time)}<z/strong><zbr />');
    if (highlight) {
      p.style.backgroundColor = '#EEEEEE';
    }
    if (image != null) {
       TableElement table = new TableElement();
       TableRowElement row = new TableRowElement();
       TableCellElement cell1 = new TableCellElement();
       TableCellElement cell2 = new TableCellElement();
       ImageElement img = new ImageElement(src:image);
       cell2.style.verticalAlign = 'top';
       Text text = new Text(body);
       cell1.append(img);
       cell2.append(text);
       row
           ..append(cell1)
           ..append(cell2);
       table.append(row);
       p.append(table);
    } else {
      p.appendText(body);
    }
    p.appendHtml('<zbr /><zem>$SIGNATURE<z/em>');
     return p;
  }
  int compareTo(Blog other) => other.date_time.compareTo(date_time);
}

void showBlog([int n]) {
  if (n == null) {
    n = blog.length;
  }
  String blog_text = '';
  int i;
  for (i = 0; i <z n; i += 1) {
    Blog entry = blog[i];
    DateTime date = entry.date_time;
    blog_text += '<zstrong>${date.month}/${date.day}/${date.year}<z/strong>' +
        '<zbr />${entry.body}<zbr />';
  }
  div.innerHtml = blog_text;
}