Firebase中的三向关系 [英] Three-Way Relationship in Firebase
问题描述
在过去的几个月中，我已经学习了很多有关非规范化数据的信息，但是我想知道在扁平化的体系结构世界中是否有可能实现以下目标.我知道如何在Firebase中处理双向关系，但是三向关系又如何.让我解释一下...
I've been learning a lot about denormalised data over the past few months, but I wanted to know if the following is possible in a flattened architecture world. I know how to handle two-way relationships in Firebase, but what about a three-way relationship. Let me explain...
我的数据库中有5个项目，分别为services，providers，serviceAtProvider，reviews和users.我希望能够将providers添加到services，反之亦然.
I have 5 items in my database, services, providers, serviceAtProvider, reviews and users. I want to be able to add providers to services and vice versa.
我还希望在service中有一个针对provider的特定页面，并且希望在该特定服务处有链接到提供者的评论.页面URL可能看起来像这样(site.com/serviceId/providerId).评级是该serviceId内部的providerId唯一的-您不能分别对serviceId s或providerId s进行评级.
I'd also like there to be a specific page for a provider inside a service, and for there to be reviews linked to the provider at that specific service. The page url might look like this (site.com/serviceId/providerId). The rating is unique to that providerId inside of that serviceId – you can't rate serviceIds or providerIds separately.
我不确定如何建立这种复杂的关系.我如何将serviceId和providerId加入该serviceAtProvider项目?
I'm not sure how to go about creating such a complex relationship. How would I join the serviceId and providerId in that serviceAtProvider item?
这是我到目前为止所得到的:
This is what I've got so far:
"services": {
"service1": {
"name": "Hernia Repair",
"providers": {
"provider1": true,
"provider2": true
}
}
},
"providers": {
"provider1": { "name": "The Whittington Hospital" },
"provider2": { "name": "Homerton Hospital" }
},
"serviceAtProvider": {
"service1AtProvider1": { "rating": 4 },
"service1AtProvider2": { "rating": 3 }
},
"reviews": {
"service1AtProvider1": {
"review1": {
"body": "A review from user 1",
"user": "user1"
}
},
"service1AtProvider2": {
"review1": {
"body": "A review from user 2",
"user": "user2"
}
}
},
"users": {
"user1": { "name": "Ben Thomas" },
"user2": { "name": "Beatrix Potter" }
}
我不知道如何创建该serviceAtProvider联接，或者我将如何访问一页上的service1.name，provider1.name，service1AtProvider1.rating，reviews.service1AtProvider1.谁能解释如何做到这一点?
I don't know how to create that serviceAtProviderjoin, or how would I go about accessing the service1.name, provider1.name, service1AtProvider1.rating, reviews.service1AtProvider1 on one page. Can anyone explain how to do this?
还有，我应该遵循什么最佳做法?
Also, are there any best practices I should follow?
感谢您的帮助.预先感谢！
Any help is appreciated. Thanks in advance!
更新
{
"availableServices": {
"service1": { "name": "Hernia Repair" },
"service2": { "name": "Chemotherapy" }
},
"services": {
"provider": {
"name": "The Whittington Hospital",
"service": {
"service1": {
"rating": 4,
"reviewId1": true
},
"service2": {
"rating": 3,
"reviewId2": true
},
}
}
},
"reviews": {
"reviewId1": {
"review1": {
"rating": 4,
"body": "A review from user 1",
"user": "user1"
}
}
},
"users": {
"user1": { "name": "Raphael Essoo-Snowdon" },
"user2": { "name": "Sharlyne Slassi" }
}
}
推荐答案
我将首先使数据结构更简单，更直接.如果没有详细的用例，很难确定适合您需求的正确数据结构.我将尽力在这里做出一些一般性的假设.您必须根据需要进行调整.
I would start by making the data structure a bit simpler and more direct. It's hard to determine the correct data structure for your needs without a detailed use case. I'll do my best to make some generic assumptions here. You'll have to adapt as necessary.
{
"service": {
"service1": { "name": "Foo Service" },
...
},
"provider": {
"provider1": { name: "Foo Place" },
...
},
"ratings": {
"service1": { // service id
"provider1": { // provider id
"average_rating": 4
},
...
},
...
},
"reviews": {
"service1": { // service id
"provider1": { // provider id
"user": "user1",
"rating": 4
},
...
},
...
},
"user": {
"user1": { "name": "Foo Bar" },
...
}
}
现在，要查找提供给定服务的提供商并获得他们的评论，我将执行以下操作:
Now, to look up the providers who offer a given service, and grab their reviews, I would do the following:
var ref = new Firebase(...);
ref.child('ratings/service1').on('child_added', function(reviewSnap) {
console.log(
'Provider ' + reviewSnap.key(),
'Average rating ' + reviewSnap.val().average_rating
);
});
可以通过多种方式加入服务和提供者的名称.这是一种手动技术:
Joining in the names of the services and providers could be done in several ways. Here's a manual technique:
var ref = new Firebase(...);
ref.child('ratings/service1').on('child_added', accumulateReview);
function accumulateReview(reviewSnap) {
var reviewData = reviewSnap.val();
var reviewid = reviewSnap.key();
fetchService(reviewSnap.parent().key(), function(serviceSnap) {
loadRec('provider', reviewSnap.key(), function(providerSnap) {
console.log('Provider: ', providerSnap.key(), providerSnap.val().name);
console.log('Service: ', serviceSnap.key(), serviceSnap.val().name);
console.log('Average rating: ', reviewData.average_rating);
});
});
}
var serviceCache = {};
function fetchService(serviceid, done) {
// demonstrates creating a local cache for things that will be
// looked up frequently
if( !serviceCache.hasOwnProperty(serviceid) ) {
cacheService(serviceid, done);
}
else {
done(serviceCache[serviceid]);
}
}
function cacheService(serviceid, done) {
loadRec('service', function(ss) {
serviceCache[serviceid] = ss;
fetchService(serviceid, done);
});
}
function loadRec(type, key, done) {
ref.child(type).child(key).once('value', done);
}
我还可以使用Firebase.util的 NormalizedCollection 自动执行此过程. a>:
I could also automate some of this process with Firebase.util's NormalizedCollection:
var ref = new Firebase(...);
var nc = Firebase.util.NormalizedCollection(
[ref.child('reviews/service1'), 'review'],
ref.child('provider'),
ref.child('user')
)
.select('review.rating', {key: 'provider.name', alias: 'providerName'}, {key: 'user.name', alias: 'userName'})
.ref();
nc.on('child_added', function(snap) {
var data = snap.val();
console.log('Provider', data.providerName);
console.log('User', data.userName);
console.log('Rating', data.rating);
});
请注意，这里没有什么是一成不变的.这就是我的处理方式.至少有几十种结构至少是一样好或更好.
Note that nothing here is set in stone. This is how I would approach it. There are probably dozens of structures at least as good or better.
这篇关于Firebase中的三向关系的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
