Ember: Ember Data results into components - ember.js

On my route im requesting via ember-data some records. Lets say the model-type is 'item'.
model: function(){
return this.get('store').find('item');
}
now ive got a component named 'my-foo' which should use the records to do something with the data. Therefore Im calling the component like that:
{{my-foo myItems=model}}
in my routes template. In the components js part, Im trying to get the myItems-field and iterate over them.
this.get('myItems').forEach(...);
Unfortunalety its not clear for me if the model i want to overgive to the component is an collection from records or just a single record (since on some routes the model is the result of store.find('item') on other store.find('item', 23424).
How can I check what kind of data arrives in the component.
(Also Im wondering what kind of object is it since im using ember-data. Is it a DS.recordarray or a promise or something else at this time?)

I can see two solutions to the problem:
Making component aware of the form that model receives
Checking and/or adjusting data type in component (in my opinion better default scenario)
As for making component aware - you could go with 2 approaches. Either differentiate in a way how your component take arguments, so there could be:
{{my-foo myItems=model}} - when you expect to receive multiple items
{{my-foo item=model}} - when you expect to receive single one
And then work accordingly further on, or - the second approach - is to actually split component (while extracting shared part to a different structure) so you would have my-foo for single items and my-foo-array for multiple.
Advantage of this approach is that you don't deal with what-if-multiple logic, that might grow to something unmanagable later on, yet usage of it is dependant on project requirements.
As for checking and/or adjusting - you already have data in, so could make assumption that your data is dirty and sanitize it using computed property. Below example, where single item is wrapped into an array.
export default Ember.Component.extend({
sanitizedItems: Ember.computed('items', function() {
var items = this.get('items');
if(!Array.isArray(items)) {
return [items];
} else {
return items;
}
})
});
Since you're using Ember.Data, depending on your setup, you might get a promise instead of object/array. In this case, you might want to resolve promise using this.get('items').then(function(items) { ... }) before doing sanitization, yet the idea behind is exactly the same.
You can check full example: Gist, Twiddle

Related

Ember Data: When do I use findAll() over query()?

This is the pattern I find myself running into:
I start making an app, and I use findAll() to get a list of [something random].
Once the app is being tested with serious data, the number of random resource instances will grow. I need to limit the number of resource instances on screen. I need to start paginating them. For this I need query string support. E.g. page[offset].
So findAll(criteria) is replaced by query(criteria, querystring).
This is a pattern so much that findAll() is starting to look like a development placeholder for query() to be used later.
I'm probably misunderstanding the use for findAll(). Is it true findAll() cannot use pagination at all (without customizing adapter code)? Can someone explain in what cases findAll() should be used?
I personally use the findAll method for fetching data that appears in various drop-downs and short lists that cannot be filtered by the user. I use query and queryRecord for pretty much everything else.
Here are a couple of particularities of findAll that can be misleading:
findAll returns all of the records present in the store along with the data that is fetched using the record's adapter.
The return of findAll is two-fold, firstly you will receive the content of the store and then it will be refreshed with the data fetched using the adapter, this behavior can be overridden using the reload flag.
To expand on Jean's answer, findAll does just that, finds all! If you had entities such as "post types" where you have [advertisement, blog, poem], findall makes sense, because you are pulling these 3 things all the time (for example in a "post creator").
Query is more precise. Say You had an api returning every car you have ever seen.
Say you had a "car" model with properties "color" and "bodyStyle"
You could use:
// find all red cars -> /cars?color=red
store.query('car', {color: 'red'});
// find all cars that are coupes -> /cars?bodyStyle=coupe
store.query('car', {bodyStyle: 'coupe'});
To your question on pagination, this is typically implemented on the API. A popular pattern is to accept/return "page" and "count" properties. These are typically found in an API payload's "meta" property.
So if you wanted to look through all cars you know of/have in your database:
// find first 10 cars -> /cars?count=10&page=1
store.query('car', {count: 10, page: 1});
// on the next page, find the next 10 cars -> /cars?count=10&page=2
store.query('car', {count: 10, page: 2});
It is worth nothing that to further your own research you should look into query parameter binding on controllers to ease the labor needed to implement a solution like this.
https://guides.emberjs.com/release/routing/query-params/
In the examples in that link you can see how you can transition to routes and use the query parameters in your store requests to fetch relevant data.
In short, findAll() is great for finding a finite set of easy to represent information, typically types of entities.
query() is great for any filtered set of results based on a criteria, as you mentioned.
Happy Coding :)
If you want "all" record of a type I would recommend using query + peekAll, this is more or less what findAll does under the hood but without various timing issues / freshness issues that findAll is subject to.
query is generally a much better API because it lets you paginate, and most apps with data of any consequence eventually hit a point they are forced to paginate either for rendering concerns or data size concerns.

Emberjs one way & two way bindings?

Lets say I want that my page's title will change depending on a really simple field what is the Ember way of doing it?
I didn't really understand the bindings in Ember, do I have to create an object even if all I need is just 1 field?
Does Ember support two way bindings? if it does so how can I constrain the bindings to one-way only?
I think i'm a bit confused with Ember-data & regular Ember, when I use Ember-data do I need to care about bindings at all?
Thanks in advance :)
This is a little vague (or I just don't fully understand what you're asking), so I'll shotgun approach and we can narrow down as you ask more questions.
Preface: Ember Data is a client side record management library, Ember works completely fine without it.
Title
A page's title is a little tricky since it's kind of out of the scope of the viewable dom, but the best way to handle it would be with an observer. In the example below, as the title property changes inside of my application controller I'm setting the document.title.
App.ApplicationController = Em.Controller.extend({
title:undefined,
watchTitle: function(){
document.title = this.get('title');
}.observes('title')
})
Example: http://emberjs.jsbin.com/haducafu/1
Computed Properties
Ember does support one way bindings (though rarely do you need to care about bindings). More often you want to care about dependent properties. eg if property a has changed, property b should be updated etc. In the case below, b is a computed property that depends on a, if a changed, b is dirty, and ember should re-computed it.
App.ApplicationController = Em.Controller.extend({
a:'foo',
b: function(){
return 'Hello: ' + this.get('a');
}.property('a')
})
Example: http://jsbin.com/haducafu/2/edit
Simple Binding
Additionally Ember can do just simple bindings (you can actually skip defining name, since ember would define it the first time it uses it).
App.ApplicationController = Em.Controller.extend({
name:undefined
});
<h2>Hello {{name}}</h2>
Name: {{input value=name}}
Example: http://jsbin.com/haducafu/3/edit
One Way/Read Only:
One way will take the value from its host property, unless you set it, if you set it it stops following the dependent property and becomes its own (not modifying the dependent property).
Read only will take values form the host property, and if you try and set it it will blow chunks.
App.ApplicationController = Em.Controller.extend({
name:'billy',
oneWay: Em.computed.oneWay('name'),
readOnly: Em.computed.readOnly('name')
});
Try changing name first, they will all update, then change oneWay and it will diverge and never return, then change readOnly and it will throw errors.
Example: http://jsbin.com/haducafu/4/edit

I just can't slice Ember Data store output

I'm JS beginner and recently using ember.js for ui development I came across a problem that I can't solve.
I'm trying to reduce amount of posts to fit them on one page. Simply calling slice method on return value of this.get('store').find() doesn't work. I also tried to trim content of return value of all function, but still without success. Any ideas?
You can use the following:
App.YourController = Ember.ArrayController.extend({
arrangedContent: function() {
return this.get('content').slice(0 , 10);
}.property('content')
});
Where YourController is the controller that belongs to your route. So the content will be the resolved promise from this.store.find('modelName'). The arrangedContent property is the place where you modify the content when you want to perform filtering, ordering etc. Without changing the content directly and preserving all the data.
Give a look in that sample http://jsfiddle.net/marciojunior/pwQ5b/
If you really are calling slice on the return value of this.get('store').find you will run into trouble. The find function returns a promise and you need the result the promise resolves to.
You can solve this in one of two ways:
If you are using the standard Ember pattern for loading in your model, you should have a model function defined in your route. This will actually wait until the result is resolved and in your controller you can call slice on this.get('content')
If you are loading your data within the controller you will need to so something like below:
c = this
this.store.find('myModel').then(function(result) {
c.set('paginatedContent', result.slice(0, 10));
});
Here we are waiting for the promise returned by find to resolve to a result before setting the paginated content based on that result.

Filtered arrays and since() functionality in ember-data

I have a backend resource that contains user activities and in the application I would like to present activities based on a single day's worth of activities. I have an ArrayController called ActivitiesController defined in the router like this:
this.resource('activities', { path: '/activities/:by_date' }, function() {
this.route('new');
});
The REST API provides the following GET method:
GET /activities/[by_date]
So far this looks pretty symmetrical and achievable but I'm running into two problems:
Parameterized array find. Typically a parameterized route would be serviced by a ObjectController but in this case the by_date parameter simply reduces/filters the array of activities but it's still an array that's returned. I'm not sure how to structure this in the model hook in the ActivitiesRoute so that its effectively doing a "findAll" rather than expecting a singular resultset.
Since functionality. As there is a reasonable network cost in bringing back these arrays of activities I would like to minimize this as much as possible and the REST API supports this by allowing for a since parameter to be passed along with the date of the last request. This way the server simply responds with a 304 code if no records have been updated since the last call and if there are new records only the new records are returned. Is there anyway to get this "out of the box" with ember-data? Does this require building a custom Adaptor? If so, are there any open source solutions that are available?
p.s. I was thinking that part of the answer to #2 might be to incorporate Alex Speller's Query Parameters: http://discuss.emberjs.com/t/query-string-support-in-ember-router/1962/48
What does your route's model hook look like? I am thinking something like this should work:
model: function(params) {
return this.store.find('activity', { by_date: params.by_date });
}

ember js compare values in DOM if statement or at least in a View with value from DOM

I been trying to compare some values in handlebars if statement {{#if value == 'otherValue'}}, obviously unsuccessfully because handlebars do not like this and expecting a string, boolean, or function name. Well that would be ok, but then I tried to pass parameter in the function like you can do with {{action}} helper, and well that didn't workout either, got this in console
Error: assertion failed: You must pass exactly one argument to the if helper
So then I decided to do this in a View, even so ember js guides points that accessing template values in-scope is unusual and they provide only poor paragraph with no examples.
http://emberjs.com/guides/understanding-ember/the-view-layer/#toc_accessing-template-variables-from-views
So when I tried to do this, I got a problem of accessing those variables, I tried this way this.get('controller.templateVariables') and via full path to View, but value was either undefined or .get() wasn't exists as a method.
So at this moment I decided to save variable in the DOM data property, but turns out this {{#view App.TabsView data-title="{{tab}}"}} is going to literately give me a string {{tab}} when I try to access it from View with this.get('data-title').
The only way left to me was to insert additional element inside view and store variable there, and afterwards access it with jQuery class selector. but element is not yet exist in the DOM at the time of isVisible function gets executed, so I have no access to values at that time. That explains why this.get('element') was returning null.
Similar examples on ember js mostly ends up with something like if (someLogic) {}, but how I can do any logic when there is no variables available to me.
Question
To simplify my question - is there a way how I can do such a thing in ember js? Simple as
// have objects stored in controller
var obj = [{title:'Tab1'}, {title:'Tab2'}, {title:'Tab3'}];
// loop via them in the DOM
obj.forEach(function(tab) {
// do this kind of comparison
if( tab.title == currentTab() ) {
// do something here
}
});
If that is not possible, then what would be the other way to achieve similar functionality?
You can write a handlerbar helper to do this
{{activeTab tab}}
Handlebars.registerHelper('activeTab', function(tab) {
})
See a question about the same issue
Active Tab
Or look at existing helpers to write your own
Bind Helper
Template Helper
I think the best way for me to demonstrate this is with a heavily commented JSFiddle that I've put together for you: http://jsfiddle.net/PbLnm/
Please ask any questions below if you're not sure about anything.
The main part which determines when to add the active class is in the computed property:
// Determine if the object we have for this view is the same as the activeTab's object. If it is the same, then this view is the current active tab.
active: function() {
return Boolean(this.get('parentView.activeTab') == this.get('tab'));
}.property('parentView.activeTab')