I'm trying to load includes on an existing model in sequelize. In express we pre check the models to see if they exist in the middleware.
So once we're in the actual "controller" we want to run some includes on that existing model that is passed in.
req.models.item.incude([
{model: Post, as: 'posts'}
])
Is there any way to accomplish this?
EDIT:
I know we can do something like this.
return req.models.item.getThing()
.then(function (thing) {
req.models.item.thing = thing;
return req.models.item;
});
But:
My expansions for includes are a dynamic property that come via url parameters, so they are not know ahead of time.
It I return the above you will not see the "thing" in the response. I need it nicely built as part of the original instance.
Something like a .with('thing', 'other.thing'); notation would be nice. Or in the case of sequelize .with({include: ...}); or .include([{model: ...}]);
If the variable req.models.item is already an Instance but without its other related instances ("includes"), then you could include them using something like the following code:
Item.findAll({
where: req.models.item.where(),
include: [{
model: SomeAssociateModel,
}]
})
.then(function(itemWithAssoc) {
// itemWithAssoc is an Instance for the same DB record as item, but with its associations
});
See here for some documentation. See here for a script demo'ing this.
Update: Given the instance, how do I just get the associated models?
To do this just use the automatically generated "getAssociation" getter functions, e.g.:
function find_associations_of_instance(instance) {
return instance.getDetails();
}
I've updated the script to include this as an example. For more information on these functions, see the SequelizeJS docs.
Here is what I am trying to understand.
Often times I find myself writing backbone like this:
var CallModel = Backbone.Model.extend({
});
var CallsCollection = Backbone.Collection.extend({
model: CallModel,
url: 'url/to/external/json'
});
It is a very basic example but as you can see, there is nothing really in the model all the data is coming into the Collection via an external url call to a json file that is build from a database.
So whats the purpose of the model? I am sure that I am probably not using backbone.js to its fullest extent which is why I am here asking you guys.
First of all, "there is nothing really in the model all the data is coming into the Collection via an external url call" - this is not true.
Let's assume you've the following:
//Model
var CallModel = Backbone.Model.extend({
defaults: {
cost:0,
duration:0
}
});
(without custom attributes or methods, there is no point in extending the original Backbone.Model)
//Collection
var CallsCollection = Backbone.Collection.extend({
model: CallModel,
url: 'url/to/external/json'
});
And the json data returned from service, probably something like:
//Response
{
callSummary: {
missed: 2,
received: 3,
totalCalls:5
totalDuration: 20
}
calls: [{
id:001,
caller:"Mr.A",
callee:"Mr.B",
cost:1,
duration:5
},{
id:002,
caller:"Mr.X",
callee:"Mrs.Y",
cost:1,
duration:7
},{
id:003,
caller:"Mr.A",
callee:"Mrs.B",
cost:1,
duration:8
}],
//and more additional information from your db
}
Now you populate your collection with data by calling it's fetch method:
CallsCollection.fetch();
Your collection should look something like:
{
models: [{
attributes: {
callSummary: {},
calls: [{},{},{}],
...
},
...
}],
length:1,
url: "url/to/external/json",
...
}
The data will be added to a model's attribute hash. If you don't specify a particular model, as Bart mentioned in his answer, backbone will populate the collection with a Backbone.Model instance: Which is still not much useful - Wew... A collection with single model having entire response data inside it's attributes as it is...
At this point, you're wondering why did I even bother creating a model, and then a collection..?
The problem here is Collections are derived from Arrays, while Models are derived from Objects. In this case, our root data structure is an Object (not an Array), so our collection tried to parse the returned data directly into a single model.
What we really want is for our collection to populate its models from the "calls" property of the service response. To address this, we simply add a parse method onto our collection:
var CallsCollection = Backbone.Collection.extend({
model: CallModel,
url: 'url/to/external/json',
parse: function(response){
/*save the rest of data to corresponding attributes here*/
return response.calls; // this will be used to populate models array
}
});
Now your collection will be something like the following:
{
models: [{
...
attributes: {
...
id:001,
caller:"Mr.A",
callee:"Mr.B",
cost:1,
duration:5
}
},{
...
attributes: {
...
id:002,
caller:"Mr.X",
callee:"Mrs.Y",
cost:1,
duration:7
}
},{
...
attributes: {
...
id:003,
caller:"Mr.A",
callee:"Mrs.B",
cost:1,
duration:8
}
}],
length:3,
url: "url/to/external/json",
...
}
This - is what we want! : Now it is very easy to handle the data: You can make use of the add, remove, find, reset and handful of other collection methods effectively.
You can pass this models array into your templating library of choice, probably with two way bindings: When the respective view for one of the call model changes, the particular model will be updated, events will propagate from your models to the collection, and the particular model will be passed into the handler functions.
You can now call fetch, save, destroy, clear and a lot of other methods with ease on single unit's of data (each model), rather than hurdle with the entire data saved in a single model - which is pretty much useless, you've to iterate through the response data manually and perform CRUD and similar operations by your own, and in most cases: re-render the entire collection view. which is very, very bad and totally unmaintainable.
To conclude: If your data source doesn't return an array of objects, or you don't parse the response and return an array of objects from which n number of models are to be populated - Then defining a collection is pretty much useless.
Hopefully, now you get the idea.
Very helpful source of info:
Backbone, The Primer: Models and Collections
Developing Backbone.js Applications
backbonejs.org
You don't need to specify a model. A Backbone collection will default to using Backbone.Model if you don't specify this option. The following would work equally well if you don't need the models of the collection to be of a particular instance.
var CallsCollection = Backbone.Collection.extend({
url: 'url/to/external/json'
});
Reference
EDIT
In essence, specifying the model option within a collection is just a way to ensure that objects added to this collection will be instances of that particular model class. If the models being added to your collection don't have any custom behaviour outside of what is available to Backbone.Model, you don't need to create and specify a model as Backbone collections will default to using an instance of Backbone.Model as I have already mentioned. If, however, you wanted to ensure that models added to a particular collection were of a particular type and shared customized behaviour (e.g. validations, defaults, etc.), you would create your own model class by extending Backbone.Model and specifying this in the collection. I hope this clears things up for you.
Sounds Weird but this is the way.
Every collection in backbone, must represent a model, so basically a collections is a list of models.
Even if your model has no data, you need to indicate it when you create a Collection.
This is how backbone works for collections.
I am trying to search through several thousand records for a particular record. I have loaded a User model and it has several thousand Shipments that are async. In other words I have the serializer send down shipment_ids with the user model.
App.User = DS.Model.extend({
shipments: DS.hasMany('shipment', { async: true })
});
I want to search through all those ids to see if a particular record's id is among them. However I don't want to go to the api and load each and every single record. I just want to be able to search through the shipment_ids.
I have a jsbin that showcases it loading all the records. How do I change this so it doesn't make any api calls for a shipment and still finds the specific record?
Instead of doing
this.get('shipments').any(function(shipment){
return shipment.get('id') === "10124";
there has to be a way to go through only the ids, no?
Thanks!
The solution described in "Get belongsTo ID without fetching record"
seems to work as of Ember Data 1.0.0-beta.10. Briefly, you can do the following to access the underlying
modelInstance.get('data.belongsToRelation.id');
Presumably you can also do this (though I have not tested it):
modelInstance.get('data.hasManyRelation');
Original Answer (DO NOT USE):
I have accomplished this on a belongsTo by adding a second model field for the id. My example:
App.User = DS.Model.extend({
group: DS.belongsTo('group', { async: true }),
groupId: DS.attr('number')
});
So maybe you can do this?
App.User = DS.Model.extend({
shipments: DS.hasMany('shipment', { async: true }),
shipmentIds: DS.attr('array')
});
You will need to add an array transform in app/transforms/array.js (assuming you use ember-cli)
import DS from 'ember-data';
var ArrayTransform = DS.Transform.extend({
deserialize: function(serialized) {
return serialized;
},
serialize: function(deserialized) {
return deserialized;
}
});
export default ArrayTransform;
Let me know if it works as I probably will need to something similar in my app soon.
This hack is very smelly but it's the only way I have found. And it is to search with _data
this.get('content._data.shipments').any(function(shipment){
return shipment.get('id') === "10124";
});
It won't make any api calls. But there has to be a more acceptable method that won't be prone to breakage when updating Ember.
Here is an updated jsbin to show this. Does anyone have a better solution?
Thanks!
Since Ember Data 2.3 you can use this code:
// get all ids without triggering a request
var commentIds = post.hasMany('comments').ids();
See http://emberjs.com/blog/2016/01/12/ember-data-2-3-released.html for details.
I'm working on a Backbone.js application with multiple "sections". Each "section" may have multiple routes but share a single collection. Here's a simple example (with sections "a" and "b"): http://jsfiddle.net/scttnlsn/LW4Ny/
In the example, all the collections are fetched when the router is initialized so that they can be shared across multiple routes without the need to re-fetch in every route handler. This seems fine at first but I am wary of continuing this way when the number of shared collections starts to grow. Additionally, it seems silly to be fetching collections for "sections" that may never even be visited by the user- I would much rather load data on demand.
The obvious alternative is to fetch the data in each route handler instead of when the router is initialized. This would mean that only data that is actually needed is fetched, however, it still ends up performing unnecessary fetches when moving between routes in the same "section". There would no longer be any "sharing" of collection data.
What's a good way to handle this situation? I feel like I need to implement some sort of cache-like structure. Are there existing solutions?
Thanks!
-Scott
Assuming I understand the issue... you could skip fetching on initialization (as in the alternative you describe), but also skip instantiation of the collection altogether until needed. Then declare a factory(ish) method:
getOrFetchCollection: function(collectionId) {
var collection = this[collectionId];
if(!collection) {
collection = this[collectionId] = new Backbone.Collection();
collection.url = urlFor(collectionId);
collection.fetch();
}
return collection;
}
Then call it from within each route handler:
a1: function() {
var view = new View({ title: 'a1', collection: this.getOrFetchCollection('a') });
show(view);
}
In this stackoverflow post i read about filtering backbone collections and using subsets.
One answer (by sled) recommends using backbone.subset.js (usage example).
I could not find any further resources on backbone.subset.js and I failed implementing it into my project.
It seems like backbone.subset.js is the perfect solution for what i'm trying to achieve.
(Having one "parent" collection that holds all models at all times, and depending on user input filtering the relevant models from the parent collection into a backbone.subset collection.)
My "parent" collection, holding all tasks:
var TasksAll = Backbone.Collection.extend({
url: '/tasks', // the REST url to retrieve collection data
model: Task // the models of which the collection consists of
});
var allTasks = new TasksAll();
Now i want to create a subset collection for e.g. tasks where task.status = 0:
var TasksTrash = new Backbone.Subset({
superset: allTasks,
filter: function(Task) {
return Task.isTrash();
}
});
var trashTasks = new TasksTrash();
Whereas inside the Task model, the method "isTrash" returns true if:
this.get('status') == 0
a) Are there any more resources on backbone.subset.js?
b) How do I implement above scenario?
c) Can I pass 'superset' and 'filter' options as params to the Backbone.Subset init function?
d) I looked into the backbone.subset.js code, when I 'reset' my parent Collection my subset Collections should be updated straight away, right?
PS: I'm fairly new to Backbone. Thanks for your help.
Looking at the source for backbone-subset, it looks as though there is a pre-initialization hook which you could utilize in order to make the 'sieve' or filter available as an option or argument:
https://github.com/masylum/Backbone.Subset/blob/master/backbone.subset.js#L50
As for providing parent as an argument, there is an outstanding patch to add that exact functionality:
https://github.com/masylum/Backbone.Subset/pull/5
With it, you can pass in parent as an option, if it is not an option the library will fall back to looking for it on the object Prototype