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11.16 串接構(gòu)造器</div>
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一個子類在實例化的時候會調(diào)用類方法<span style="color: #0000FF">new</span><span style="color: #800080">()</span>。在函數(shù)中定義的任何代碼執(zhí)行之前，<span style="color: #0000FF">new</span><span style="color: #800080">()</span>執(zhí)行的一個動作是調(diào)用其超類的<span style="color: #0000FF">new</span><span style="color: #800080">()</span>方法，并且會沿著繼承樹按這種方式一直向上調(diào)用。因此，所有的構(gòu)造器都會按正確的順序調(diào)用，它們都是起始于根基類并結(jié)束于當前的類。 </p>
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如果超類的初始化方法需要參數(shù)，那么會有兩種選擇：一種選擇是總是提供相同的參數(shù)，另外一種選擇是使用super關(guān)鍵字。如果參數(shù)總是相同的，那么它們可以在被擴展的時候指定： </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00369"><pre class="Element12"><span style="color: #0000FF">class</span> EtherPacket <span style="color: #0000FF">extends</span> Packet<span style="color: #800080">(</span><span style="color: #FF0000">5</span><span style="color: #800080">);</span></pre></div></div>
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這個例子將<span style="color: #FF0000">5</span>傳遞到與<i>Packet</i>相關(guān)聯(lián)的<span style="color: #0000FF">new</span>例程。 </p>
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一個更加通用的方法是使用<span style="color: #0000FF">super</span>關(guān)鍵字來調(diào)用超類構(gòu)造器： </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00370"><pre class="Element12"><span style="color: #0000FF">function</span> <span style="color: #0000FF">new</span><span style="color: #800080">();</span>
<span style="color: #0000FF">super</span><span style="color: #800080">.</span><span style="color: #0000FF">new</span><span style="color: #800080">(</span><span style="color: #FF0000">5</span><span style="color: #800080">);</span>
<span style="color: #0000FF">endfunction</span></pre></div></div>
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為了使用這個方法，<span style="color: #0000FF">super</span><span style="color: #800080">.</span><span style="color: #0000FF">new</span><span style="color: #800080">(</span><span style="color: #FF0000">5</span><span style="color: #800080">)</span>必須是new函數(shù)執(zhí)行的第一條語句。</p></div>
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