小程序数据绑定错误？

Question

为何AppData中没有postData对象？且页面显示空白？
post.js
Page({
data:{
},
onLoad:function(){

var iceCreamData={
  object:{
    date: "Jan 28 2017"
  },
  title: "小时候的冰棍儿与雪糕",
  postImg: "/images/post/post-4.jpg",
  avatar:"/images/avatar/avatar-5.png",
  content:"冰棍与雪糕绝对不是同一个东西。3到5毛钱的雪糕犹如现在的哈根达斯，而5分1毛的冰棍儿就像现在的老冰棒。时过境迁，...",
  readingNum:92,
  collectionNum:{
    array: [108]
  },
  commentNum: 7
},
this.setData({
  postData: iceCreamData
})

}
})

post.wxml
<view>
<view class='post-container'>

<view class='post-author-date'>
  <image src='{{postData.avatar}}'></image>
  <text>{{postData.object.date}}</text>
</view>
<text class='post-tittle'>{{postData.title}}</text>
<image class='post-image' src="{{postData.postImg}}" mode='aspectFill'></image>
<text class='post-content'>{{postData.content}}</text>
<view class='post-like'>
  <image src='/images/icon/wx_app_collect.png'></image>
  <text>{{postData.collectionNum.array[0]}}</text>
  <image src='/images/icon/wx_app_view.png'></image>
  <text>{{postData.readingNum}}</text>
  <image src='/images/icon/wx_app_message.png'></image>
  <text>{{postData.commentNum}}</text>
</view>

</view>
</view>
</view>