Allow user to specify a Backbone model's ID at creation time - javascript

When saving a model, Backbone determines whether to send an HTTP POST or PUT request by whether or not the model's ID attribute is set. If there is an ID, the model is considered to already exist.
For my application, this logic is incorrect because I must allow the user to specify an ID (as I interact with a poorly designed legacy system).
How should I handle this problem? I still would like to use PUT if the model is changed.
I am considering the following options:
Override isNew, which is the Backbone method that simply checks if an ID is present.
Override sync.
Determine if the concept of cid would somehow solve the problem.

One solution is to address the symptoms rather than the cause. Consider adding to your model a new create method:
var FooModel = Backbone.Model.extend({
urlRoot: '/api/foo',
create: function () {
return this.save(null, {
type: 'post', // make it a POST rather than PUT
url: this.urlRoot // send the request to /api/foo rather than /api/foo/:id
});
}
});
This is the solution I use, but I don't consider it ideal because the view logic/caller now needs to call create rather than save when creating (which is rather easy to do). This extended API bothers me for my use-case (despite working and being rather small), but perhaps it'll work for yours.
I'd love to see some additional answers to this question.

So I went down the path of trying to change up isNew.
I came up with new criteria that would answer whether a model is new:
Was the model created via a fetch from a collection? Then it's definitely not new.
Was the model created with an ID attribute? This is a choice I made for my case, see disadvantages below for the effect of doing this, but I wanted to make new Model({ id: 1, name: 'bob' }) not be considered new, while setting the ID later on (new Model({ name:
bob'}).set('id', 1)) would be.
Was the model ever synced? If the model was successfully synced at any point, it's definitely not new because the server knows about it.
Here's what this looks like:
var UserDefinedIDModel = Backbone.Model.extend({
// Properties
_wasCreatedWithID: false,
_wasConstructedByFetch: false,
_wasSynced: false,
// Backbone Overrides
idAttribute: 'some_id',
urlRoot: '/api/foo',
constructor: function (obj, options) {
this._wasCreatedWithID = !!obj[this.idAttribute];
this._wasConstructedByFetch = options && options.xhr && options.xhr.status === 200;
// Preserve default constructor
return Backbone.Model.prototype.constructor.apply(this, arguments);
},
initialize: function () {
this.on('sync', this.onSync.bind(this));
},
isNew: function () {
// We definitely know it's not new
if (this._wasSynced || this._wasConstructedByFetch) return false;
// It might be new based on this. Take your pick as to whether its new or not.
return !this._wasCreatedWithID;
},
// Backbone Events
onSync: function () {
this._wasSynced = true;
}
});
Advantages over the other answers
No logic outside of the backbone model for handling this odd usecase.
No server-side changes to support this
No new pseudo properties
Disadvantages
This is a lot of code when you could just create a new create method as per my other answer.
Currently myCollection.create({ some_id: 'something' }); issues a PUT. I think if you need support for this you'll have to do myCollection.create({ some_id: 'something' }, { url: '/api/foo', type: 'post' }); You can remove the _wasCreatedWithoutID check to fix this, but then any construction of a new model that derives its data from an existing one will be treated as new (in my case, this is undesirable).

Here's another solution :
In your model define an idAttribute that don't exists in your server model/table/... and that wouldn't be displayed to the DOM.
So let's suppose that the JSON that you send to the server is as follows :
{
'id': 1,
'name': 'My name',
'description': 'a description'
}
Your model should look like :
var MyModel = Backbone.Model.extend({
idAttribute: 'fakeId'
});
Now, when you create a new model and try to save it to the server, no one would initialize the fakeId and it would be considered a new object (POST).
When you fetch your model from the server you have to set the fakeId in your model, and your server must duplicate the id in the fakeId like this your model will be considered as an existing (PUT)

Related

Backbone sync issue firing POST instead of PUT

I have written the following code in my model:
urlroot: '/url/sms',
setAuthId: function(value) {
var _this = this ;
if (this.get("smsauth") != value) {
this.set("smsauth",value);
this.save();
//Ideally, I want to achieve this AJAX call request with backbone.
// $.ajax({
// url: "/url/sms",
// data: value,
// type: 'PUT',
// processData: false,
// success: function(result) {
// _this.set("authId", value);
// },
// error : function(){
// console.log('Error setting authid');
// }
// });
}
},
Ideally, we should be firing a "PUT" request everytime. But the backbone is firing a POST request because "ID" is not present.
I'm quite new to backbone, I was wondering if there is anyway to sync with server without having to pass an ID? How can I solve this problem?
I basically want to fire a PUT request NOT post request for the URL. (Since my backend only supports PUT request).
The only real way to force Backbone.Model.save() to do a PUT is the way #dbf explained, you have to set your idAttribute. To properly set idAttribute your model should have an attribute that is unique. (This is not a hard requirement, since model.isNew() just checks that your model has a property named id or whatever string you supply to your model idAttribute property. It doesn't check for uniqueness).
I sense that in your case, you may not have a unique attribute in your models, so setting idAttribute may be a challenge. For that reason, I suggest you don't specify an idAttribute in your model definition. Rather, we just handle it dynamically.Just refactor your code like this:
setAuthId: function(value) {
var _this = this ;
if (this.get("smsauth") != value) {
// any model attribute is fine, we just need to return a prop
this.prototype.idAttribute = "smsauth"
this.save("smsauth",value) // Save will do a set before the server request
// model.save returns a promise. Here we'll reset the idAttribute
.then(/* success handler */ function (response) {
_this.set("authId",value);
_this.prototype.idAttribute = 'id' // You can set this to "authId" if that
// uniquely identifies this model
},/* error handler */ function (response) {
_this.prototype.idAttribute = 'id' // reset idAttribute to default
});
}
}
It's not really clear to me what you are saving. The fact you are handling with POST suggest its a new entry. Quoting from the docs this behaviour is correct. PUT is update, POST is create (under CRUD operations).
If the model isNew, the save will be a "create" (HTTP POST), if the
model already exists on the server, the save will be an "update" (HTTP
PUT).
What you might try is what #Sami suggest by overwriting the save with an update request (do realise that all solutions here are incorrect/workarounds).
If you really need PUT and cannot alter your backend for some mysterious reason to accept POST, you could change the idAttribute within the model.
var smsModel = Backbone.Model.extend({
idAttribute: "smsauth" // for example
});
Do realise that your backend, very likely, has a design flaw where you are changing and creating workarounds to work with it, which you should consider to avoid.
I have used this snippet.
this.save({}, {
type: 'PUT'
});
I found all your answers really fascinating, I am going to try everyone of them.
Thanks for your suggestions, this is why I like SO. Something new to learn.
You can override save method.
Something like
var model = Backbone.Model.extend({
save: function(options){
return Backbone.sync("update", this, options);
}
});

backbone.stickit and html-form: How to save (patch) only changed attributes?

tl;dr
How to use backbone.stickit with a html form to change an existing model fetched from the server and only PATCH the changed attributes (changed by user input within the html form) to the server?
/tl;dr
I'm using backbone.stickit in a backbone.js application to bind a model to a HTML-form which is part of a backbone view. This works fine so far, but it becomes a little bit complicated if I'm going to save the bound model. This is because I want to use the PATCH-method and only send the changed attributes to the server. I try to illustrate what I've done so far:
Fetching the model from Server
user = new User(); //instatiate a new user-model
user.fetch(); //fetching the model from the server
console.log(user.changedAttributes()); // Returns ALL attributes, because model was empty
The last line indicates my problem, because I thought I can used the changedAtrributes() method later to get the attributes which need a patch on the server. So I tried this workaround which I found here
user.fetch({
success: function (model, response, options) {
model.set({});
}
});
user.changedAtrributes(); //Returns now "false"
Do stickit-bindings
Now I render my view and call the stickit() method on the view, to do the bindings:
//Bindings specified in the view:
[...]
bindings: {
"#username" : "username"
"#age" : "age"
}
[...]
//within the render method of the view
this.stickit();
The bindings work fine and my user model gets updated, but changedAttributes() remain empty all the time.
Save the model to the server
If the user has made all required changes, the model should be saved to the server. I want to use the PATCH method and only send the changed attributes to the server.
user.save(null, {patch:true}); //PATCH method is used but ALL attributes are sent to the server
OR
user.save(user.changedAttributes(),{patch : true});
With the second approach there are different outcomes:
if I didn't use the user.set({}) woraround, all attributes get PATCHED to the server
if I use the user.set({}) woraround the return value of changedAttributes() is "false" and all attributes are PUT to the server
if I call a user.set("age","123") before calling save(), then only the age attribute is PATCHED to the server
So outcome 3 is my desired behaviour, but there are 2 problems with this: First stickit doesn't seem to use the set() method on the model to update the attributes if they are changed within the html-form. And second, if you call set() with one attribute and afterwards with another, only the second attributes is returned by changedAttributes().
Maybe I just overseen something in the backbone or backbone.stickit docs, so I didn't get the desired behaviour working. Any ideas about that?
NOTE: As found out the problem wasn't directly related to backbone.stickit, more to backbone itself.
Solved this problem on my own, maybe this helps someone who may stumble upon this question:
Backbone only keep track of unchanged attributes, but not of unsaved attributes. So with
model.changedAttributes();
you will only get the attributes of the model, which was changed since the last
model.set("some_attribute","some_value")
Finally I stumbled upon backbone.trackit which is a backbone.js plugin maintained by the creator of backbone.stickit. With this plugin you can track unsaved attributes (all attributes which have changed since the last model.save()) and then use them in the save-method of a model. Example (my usecase):
Backbone.View.extend({
bindings: {
"#name" : "name",
"#age" : "age"
},
initialize: function () {
this.model = new User();
this.model.fetch({
success: function (model, response, options) {
//this tells backbone.stickit to track unsaved attributes
model.startTracking();
}
});
},
render: function () {
this.$el.html(tmpl);
this.stickit();
return this;
},
onSaveUserToServer: function () {
//first argument: only unsaved attributes, second argument: tell backbone to PATCH
this.model.save(this.model.unsavedAttributes(), { patch: true });
});
});

Optimal URL structure for Backbone.js and Backbone implementation

I'm developing a RESTful API for a Quiz app, which is going to be built with Backbone.js and Marionette. I'm quite new to backbone and was wondering what de best URL structure would be. I have the following resources:
Answer,
Question which contains Answers,
Question Group which contains Questions,
Quiz which contains Question Groups.
Two possible URL structures come to mind:
GET /quizzes/:id
GET /quizzes/:id/questiongroups
GET /quizzes/:id/questiongroups/:id
GET /quizzes/:id/questiongroups/:id/questions
GET /quizzes/:id/questiongroups/:id/questions/:id
GET /quizzes/:id/questiongroups/:id/questions/:id/answers
or:
GET /quizzes/:id
GET /quizzes/:id/questiongroups
GET /questiongroups/:id
GET /questiongroups/:id/questions
...
Now, I have been trying to use both of these options. With the first one, I can't figure out how to define the collections as a property of the parent models in Backbone so that I can use fetch() on them. The problem with the second option is a bit different: as I understand it, Backbone derives the url for a model from its collection, but the collection is a child of another resource, whereas the url for getting a single resource uses another collection, namely the global set of resources.
I'm pretty sure I'd have to override url() in both cases. I tried some things but didn't come up with anything useable at all. Also, I'd rather not override every single url()-model in the app, changing the API structure to suit the preferences of Backbone seems like a better option to me.
Any pointers as to what seems the right way to do it with Backbone would be great!
Thanks
If questiongroups can only appear in a single quiz, then the first option (the hierarchical one) is an obvious choice. To comply with RESTful conventions, you might want to consider using singular nouns instead: /quiz/:id/questiongroups/:id/question/:id/answer/:id
To solve your fetching problem, I would recommend using nested backbone models as per this answer: https://stackoverflow.com/a/9904874/1941552. I've also added a cheeky little parentModel attribute.
For example, your QuizModel could look something like this:
var Quiz = Backbone.Model.extend({
urlRoot: '/quiz/', // backbone appends the id automatically :)
defaults: {
title: 'My Quiz'
description: 'A quiz containing some question groups.'
},
model: {
questionGroups: QuestionGroups,
},
parse: function(response){
for(var key in this.model){
var embeddedClass = this.model[key];
var embeddedData = response[key];
response[key] = new embeddedClass(embeddedData, {
parse:true,
parentModel:this
});
}
return response;
}
});
Then, your QuestionGroups model could have the following url() function:
var QuestionGroups = Backbone.Model.extend({
// store metadata and each individual question group
url: function() {
return this.parentModel.url()+'/questiongroup/'+this.id;
}
});
Alternatively, if you don't need to store any metadata, you could use a Backbone.Collection:
var QuestionGroups = Backbone.Collection.extend({
model: QuestionGroup,
url: function() {
return this.parentModel.url()+'/questiongroup/'+this.id;
}
});
I'm afraid I haven't tested any of this, but I hope it can be useful anyway!

How to add a new many relationship to parent model?

Disclaimer: I tried to make a jsfiddle of this, but without a public source for the RESTAdapter, I couldn't really make it work.
I have a model with a hasMany array of child models. I need to add a new model to this child array and save to the server:
App.FooModel = DS.Model.extend({
'name': DS.attr('string'),
'bars': DS.hasMany('App.BarModel')
});
App.BarModel = DS.Model.extend({
'name': DS.attr('string'),
});
App.ApplicationController = Ember.Controller.extend({
init: function() {
var foo = App.FooModel.find(101); // -- currently has bars[201, 202, 203]
var newBar = loadFixture( App.BarModel, 204 );
var self = this;
setTimeout( function() { // -- just to be sure our models are loaded before we try this
// foo.currentState: saved
foo.get('bars').addObject(newBar);
// foo.currentState: saved
foo.store.commit(); // -- nothing happens
}, 1000);
}
});
App = Ember.Application.create({
store: DS.Store.create({
revision: 11
})
});
But nothing happens. My parent model doesn't get marked as dirty, so the store never attempts a commit. Is there a different way I should be adding this relationship to the parent? Is this a bug?
Current Workaround:
foo.get('bars').addObject(newBar);
var save = foo.get('name');
foo.set('name', (save + '!'));
foo.set('name', save); // -- this marks our record as dirty, so a save will actually happen
foo.store.commit();
Edit 1: I'm aware that ember-data will only serialize this data if it was embedded to begin with (https://stackoverflow.com/a/15145803/84762), but I have overridden my serializer to handle this. The issue I'm having is that the store never even attempts to save this change so we never even get to the serializer.
Edit 2: I suspect this might have something to do with this bug, but at the same that would mean this wouldn't work for anyone and I have a hard time believing no one else has run into this, yet.
It looks like you're Modeling a one to many relationship yet you didn't include the belongsTo option on App.BarModel. Check this link out:
http://emberjs.com/guides/models/defining-models/#toc_one-to-many
App.Post = DS.Model.extend({
comments: DS.hasMany('App.Comment')
});
App.Comment = DS.Model.extend({
post: DS.belongsTo('App.Post')
});
For what I understand, you did not use the embedded feature of relationship but overrided your serializer to handle the serialization of bars objects into foo object.
I think your bug probably came from here : if your relation is not embedded there is no reason to mark the foo object dirty as when you add an object to his bars association what should change is usually a key foo_id of the bar object you added, then there is no changes of the foo object to send to the API.

Backbone Model: Keep Collection when saving

I have a simple Backbone model that looks like this:
(function () {
App.Company = Backbone.Model.extend({
defaults: {},
urlRoot: "/Contacts/Companies",
initialize: function () {
var contactPersons = this.get("ContactPersons") || [];
this.set("ContactPersons", new App.ContactPersonCollection(contactPersons));
}
});
})();
Whenever I save the model to the server, the ContactPersons collection is reset to an Array.
Is it really necessary for me to manually turn it into a collection, after a model is saved?
UPDATE: This works as intended -- See answer for better approach (IMHO)
(function () {
App.Company = Backbone.Model.extend({
defaults: {},
urlRoot: "/Contacts/Companies",
initialize: function () {
var contactPersons = this.get("ContactPersons") || [];
if (_.isArray(contactPersons)) {
this.set("ContactPersons", new App.ContactPersonCollection(contactPersons));
}
},
parse: function (response) {
if (response.ContactPersons && _.isArray(response.ContactPersons)) {
response.ContactPersons = new App.ContactPersonCollection(response.ContactPersons);
}
return response;
}
});
})();
When you send data back from the server, how are you handling the response? For example if you just send back a [{},{},{}] I don't think Backbone automatically knows to treat that as a collection. Thus, it sets the ContactPersons attribute as what it gets, your vanilla array.
What you can do, is override your set function inside your model which will take the array of objects passed in and write to the collection as proper. See this example:
set: function(attributes, options) {
if (_.has(attributes, 'ContactPersons') && this.get("ContactPersons")) {
this.get('ContactPersons').reset(attributes.ContactPersons);
delete attributes.ContactPersons;
}
return Backbone.Model.prototype.set.call(this, attributes, options);
}
So basically as long as your server response is properly namespaced (response.ContactPersons) then after parsing it will pass your response to the set function. The collection data is treated specially as a collection. Here, I'm just reseting the collection that already exists with the new data. All your other model attributes should continue to be passed on to the original set().
UPDATE - Growing doubt about own answer
I haven't been able to get this question/answer out of my mind. It certainly works, but I'm becoming unconvinced that using a modified set() vs. just doing things in parse() is any better. If someone has some comments on the difference between using a modified set() vs. parse() with nested models, I'd really welcome the input.

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