<h3 dir="auto">Version</h3>
<p dir="auto">2.6.14</p>
<h3 dir="auto">Reproduction link</h3>
<p dir="auto"><a href="https://codesandbox.io/s/lively-monad-ukyzf?file=/src/App.vue" rel="nofollow">codesandbox.io</a></p>
<h3 dir="auto">Steps to reproduce</h3>
<p dir="auto">打开链接 直接在页面中的 输入框输入内容即可复现该错误</p>
<h3 dir="auto">What is expected?</h3>
<p dir="auto">name 的值应该正确的被设置</p>
<h3 dir="auto">What is actually happening?</h3>
<p dir="auto">报错 TypeError: _vm.$set is not a function<br>
我发现是因为 _vm 没有 $set 方法导致的，此时 _vm.$set 如果被渲染成 _vm.injections.rootNode.$set 就没有问题了</p>
<h3 dir="auto">Vue.js version</h3>
<p dir="auto">2.0 rc</p>
<h3 dir="auto">Reproduction Link</h3>
<p dir="auto"><a href="http://codepen.io/anon/pen/xEqbmN?editors=1010#0" rel="nofollow">http://codepen.io/anon/pen/xEqbmN?editors=1010#0</a></p>
<h3 dir="auto">What is Expected?</h3>
<p dir="auto">Not sure if this is what is expected in Vue 2.0. Tried to search but couldn't find anything.<br>
e.g:</p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="data: {
  model: {
    a: ''
  }
}"><pre class="notranslate">data: <span class="pl-kos">{</span>
  <span class="pl-c1">model</span>: <span class="pl-kos">{</span>
    <span class="pl-c1">a</span>: <span class="pl-s">''</span>
  <span class="pl-kos">}</span>
<span class="pl-kos">}</span></pre></div>
<div class="highlight highlight-text-html-basic notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="&lt;input v-model=&quot;model.a&quot; /&gt;
&lt;input v-model=&quot;model.b&quot; /&gt;"><pre class="notranslate"><span class="pl-kos">&lt;</span><span class="pl-ent">input</span> <span class="pl-c1">v-model</span>="<span class="pl-s">model.a</span>" /&gt;
<span class="pl-kos">&lt;</span><span class="pl-ent">input</span> <span class="pl-c1">v-model</span>="<span class="pl-s">model.b</span>" /&gt;</pre></div>
<p dir="auto">If you pass an uninitialized property (<code class="notranslate">model.b</code>) to <code class="notranslate">v-model</code>, it's obviously not reactive so bindings won't update or a deep watch on <code class="notranslate">this.model</code> won't fire off either.</p>
<p dir="auto">Any chance that <code class="notranslate">v-model</code> could use <code class="notranslate">Vue.set</code> internally if it detects a binding with value <code class="notranslate">undefined</code> to automatically create reactive properties? (like Vue 1.0)</p>
<p dir="auto">Or failing that, it should <code class="notranslate">warn</code> when an uninitialized property is passed to <code class="notranslate">v-model</code></p>