我试图找出这个嵌套的顺序,我所做的一切都不会起作用 .
以下是我尝试订购的数据结构示例:
{
"-KV_Lrm_93Agm8kAuXql": {
"body": {
"Acceleration": "0.0",
"Altitude": "11",
"Battery": "12.7",
"Date": "2016/09/10",
"order": 1,
"time": "2016-10-19T20:26:32Z"
}
},
"-KV_LuTfJ9VrKRHoRWuw": {
"body": {
"Acceleration": "0.0",
"Altitude": "11",
"Battery": "12.7",
"Date": "2016/09/10",
"order": 5,
"time": "2016-10-21T20:26:32Z"
}
},
"-KV_Lx9VABuEB8D3I-i1": {
"body": {
"Acceleration": "0.0",
"Altitude": "11",
"Battery": "12.7",
"Date": "2016/09/10",
"order": 2,
"time": "2016-10-01T20:26:32Z"
}
},
"-KV_LzQOM3rHEKQuwyHQ": {
"body": {
"Acceleration": "0.0",
"Altitude": "11",
"Battery": "12.7",
"Date": "2016/09/10",
"order": 10,
"time": "2016-09-01T20:26:32Z"
}
},
"-KV_M0fdznAbKanHoY91": {
"body": {
"Acceleration": "0.0",
"Altitude": "11",
"Battery": "12.7",
"Date": "2016/09/10",
"order": 6,
"time": "2016-09-20T20:26:32Z"
}
}
}
根据firebase文档(https://firebase.googleblog.com/2015/09/introducing-multi-location-updates-and_86.html),您可以执行"deep path query" . 在我的情况下,如果我想按 order 排序,我应该能够:
.orderByChild("body/order")
但这没有任何作用 . 它对结果的排序没有影响 . 我也试过订购日期和时间,但都没有工作 . 这是我的完整节点功能 . 这将返回结果,只是没有订购:
app.get('/api/xirgo-data', function(req, res)
{
var ref = db.ref("xirgo");
ref
.orderByChild("body/order")
.on("value", function(snap) {
return res.json(snap.val());
});
});
谢谢!
1 回答
在Firebase中请求查询值时,生成的快照包含匹配子项的键,值和排序信息 .
但是当您将其转换为字典/关联数组/ JavaScript对象时,由于JavaScript对象本质上是无序的,因此排序信息会丢失 .
要确保您能够以正确的顺序访问匹配项,请使用内置的
DataSnapshot.forEach()
方法: