Was*_*eem 5 javascript angularjs firebase angularfire
我在firebase中有数据如下所示:
"application": {
"companies": {
"firebase": {
"creation": {
"name": "Firebase Inc",
"location": "USA"
},
"google": {
"creattion": {
"name": "Google Inc",
"location": "USA"
}
}
"facebook": {
},
"apple": {
}
}
}
}
companies密钥下有成千上万的记录.我如何有效地执行以下查询？
如何仅查询creation其名称下存在密钥的记录？
如何只查询creation名称下没有密钥的记录？
我还想调用.on('child_added')返回的结果集,以便稍后我只能处理那些特定的记录.可能吗？
Sin*_*lel 11
以下是无需使用额外参数即可执行此操作的查询:
creation:
var ref = new Firebase(fbUrl+'/companies').orderByChild("creation").equalTo(null);creation:
var ref = new Firebase(fbUrl+'/companies').orderByChild("creation").startAt(!null);".indexOn": "creation"规则.编辑2:我很好奇,所以我把11,000条记录推到了/companies2(一半有creation孩子,有一半没有).我可以使用上面的查询(或我在下面显示的变体之一)在~4秒内检索5500个匹配记录.
编辑3:如果您经常运行这些查询,那么/companies根据存在的情况将孩子分成两个箱子可能是值得的creation.这样,您可以单独阅读这两个段,而无需依赖查询.
这是修改后的工厂的样子(我修改了PLNKR以匹配):
app.factory("CompaniesFactory",function($q, fbUrl){
return function(hasCreation){
var deferred = $q.defer();
var ref = new Firebase(fbUrl+'/companies').orderByChild("creation");
var query;
if (hasCreation) {
query = ref.startAt(!null);
// or:
// query = ref.startAt(true);
} else {
query = ref.equalTo(null);
// or:
// query = ref.endAt(!null);
// query = ref.endAt(true);
}
query.once("value", function(dataSnapshot){
deferred.resolve(dataSnapshot.val());
}, function (error) {
deferred.reject(error);
});
return deferred.promise;
}
});
是的,可以调用.on('child_added')返回的dataSnapshot.请参见DataSnapshot.ref().
(保留此参考)
另一种方式来做到这一点是通过添加另一个参数调用hasCreation到的孩子companies有creation由,和查询.
var ref = new Firebase(fbUrl+'/companies').orderByChild("hasCreation").equalTo(hasCreation);
hasCreation在查询中null,查询将返回没有hasCreation子项的公司.hasCreation在查询中true,查询将返回公司hasCreation===true.{
"company1" : {
"creation" : {
"name" : "company1"
},
"hasCreation" : true
},
"company2" : {
"name" : "company2"
},
"company3" : {
"name" : "company3"
},
"company4" : {
"creation" : {
"name" : "company4"
},
"hasCreation" : true
}
}
您可以".indexOn" : "hasCreation"像这样添加规则:
"so:29179389":{
".read" : true,
".write" : true,
"companies" : {
".indexOn" : "hasCreation"
}
}
app.factory("CompaniesFactory",function($q, fbUrl){
return function(hasCreation){
var deferred = $q.defer();
if (!hasCreation) {
hasCreation = null;
}
var ref = new Firebase(fbUrl+'/companies').orderByChild("hasCreation").equalTo(hasCreation);
ref.once("value", function(dataSnapshot){
deferred.resolve(dataSnapshot.val());
});
return deferred.promise;
}
});
app.controller('HomeController',function($scope,fbUrl,CompaniesFactory) {
$scope.getCompanies = function(hasCreation) {
var companies = new CompaniesFactory(hasCreation).then(function(data){
console.log(data);
$scope.companies = data;
});
}
});
<body ng-app="sampleApp">
<div ng-controller="HomeController">
<button ng-click="getCompanies(true)">Find with creation</button>
<button ng-click="getCompanies(false)">Find without creation</button>
<h2>Companies:</h2>
{{companies}}
</div>
</body>
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