tyle="color:#999988;font-style:italic">// 每次 get 时如果有订阅者则添加订阅</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">      </span><span class="token keyword" style="color:#00009f">if</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">Dep</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">target<