I would like to do something like:
App.Model.find({unique_attribute_a: 'foo'}).objectAt(0).get('attribute_b')`
basically first finding a model by its unique attribute that is NOT its ID, then getting another attribute of that model. (objectAt(0) is used because find by attribute returns a RecordArray.)
The problem is App.Model.find({unique_attribute_a: 'foo'}).objectAt(0) is always undefined. I don't know why.
Please see the problem in the jsbin.
It looks like you want to use a filter rather than a find (or in this case a findQuery). Example here: http://jsbin.com/iwiruw/438
App.Model.find({ unique_attribute_a: 'foo' }) converts the query to an ajax query string:
/model?unique_attribute_a=foo
Ember data expects your server to return a filtered response. Ember Data then loads this response into an ImmutableArray and makes no assumption about what you were trying to find, it just knows the server returned something that matched your query and groups that result into a non-changable array (you can still modify the record, just not the array).
App.Model.filtler on the other hand just filters the local store based on your filter function. It does have one "magical" side affect where it will do App.Model.find behind the scenes if there are no models in the store although I am not sure if this is intended.
Typically I avoid filters as it can have some performance issues with large data sets and ember data. A filter must materialize every record which can be slow if you have thousands of records
Someone on irc gave me this answer. Then I modified it to make it work completely. Basically I should have used filtered.
App.Office.filter( function(e){return e.get('unique_attribute_a') == 'foo'}).objectAt(0)
Then I can get the attribute like:
App.Office.filter( function(e){return e.get('unique_attribute_a') == 'foo'}).objectAt(0).get('attribute_b')
See the code in jsbin.
Does anyone know WHY filter works but find doesn't? They both return RecordArrays.
Related
I'm developing an web app with Django to query and download data from multiple weather stations. It's almost everything good but something that I don't like it's that when I filter by stations, the form passes them to the URL like this:
https://my-server/stations?station_name=1&station_name=2&station_name=3
And since the number of selected stations can reach more than 250 (this added to the fact that spatial data are also passed in the URL as coordinates, polygons...), I would like to know if there is any way to obtain the "station_name" parameter in a list format like this or similar, for me to later divide it in my views.py:
https://my-server/stations?station_name=1%3B2%3B3
On the other hand, I'm not sure if there are any contraindications when generating too long URLs, if not I have no problem maintaining the current format, but otherwise I would like to find a solution.
Thanks in advance
Edit: If it helps, I'm using the Select2MultipleWidget widget for this field.
My code
PriceListItem.objects.get(id=tarif_id).price_eur
In my settings.py
CURRENCY='eur'
My Question:
I would like to pick the different info depending on the CURRENCY variable in settings.py
Example:
PriceListItem.objects.get(id=tarif_id).price_+settings.CURRENCY
Is it possible?
Sure. This has nothing to do with Django actually. You can reach the instance's attribute through pure Python:
getattr(PriceListItem.objects.get(id=tarif_id), 'price_'+settings.CURRENCY)
Note it might be a better idea to have a method on the model which accepts the currency as a parameter and returns the correct piece of data (through the line I wrote above, for example).
I think this should work
item = PriceListItem.objects.get(id=tarif_id)
value = getattr(item, price_+settings.CURRENCY)
In case you are only interested in that specific column, you can make the query more efficient with .values_list:
my_price = PriceListItem.objects.values_list_(
'price_{}'.format(settings.CURRENCY),
flat=True
).get(id=tarif_id)
This will only fetch that specific column from the database, which can be a (a bit) faster than first fetching the entire row into memory, and then discard all the rest later.
Here my_price is thus not a PriceListItem object, but the value that is stored for the specific price_cur column.
It will thus result in a query that looks like:
SELECT pricelistitem.price_cur
FROM pricelistitem
WHERE id=tarif_id
this.store.findAll('game').then(function(results){
// RUN SOME OPERATION ON THEM
})
I would like to know how I can play with the results variable. I understand I can do
results.get('firstObject') // returns the first object.
I'd like to know everything else I can do with it. Is there any api documentation for the results collection?
Thanks!
From ember guides,
The below methods, will return the Promise, it will be resolved to Record or RecordArray.
store.findAll() returns a DS.PromiseArray that fulfills to a DS.RecordArray.
store.findRecord returns a promise that will be resolved with the record.
store.query() returns a DS.PromiseArray in the same way as findAll.
The below two are synchronus method, it will retrieve what is available in the store and returns record itself. it will not request the server to fetch data.
store.peekAll directly returns a DS.RecordArray.
store.peekRecord direclty returns record
It's important to note that DS.RecordArray is not a JavaScript
array, it's an object that implements Ember.Enumerable. This is
important because, for example, if you want to retrieve records by
index, the [] notation will not work--you'll have to use
objectAt(index) instead.
From Ember.Enumerable, most of the time I happened to use the following,
forEach to iterate
map to transform to new Array
filterBy findBy for filtering based on single property check
toArray converting to normal native array
findAll will return a Promise which will resolve to a RecordArray.
The RecordArray is an ArrayProxy.
http://emberjs.com/api/classes/Ember.ArrayProxy.html
This is everything you need.
If you google "ember findall" you will find docs for "Ember.js - Models: Finding Records - Guides" as well.
https://guides.emberjs.com/v2.5.0/models/finding-records/
I'm reviewing some code and I came across a line that does the following:
Person.find_by(name: "Tom").id
The above code gets the FIRST record with a name of "Tom", then builds a model, then gets the id of that model. Since we only want the id, the process of retreiving all data in the model and initializing the model is unneeded. What's the best way to optimize this using active record queries?
I'd like to avoid a raw sql solution. So far I have been able to come up with:
Person.where(name: "Tom").pluck(:id).first
This is faster in some situations since pluck doesn't build the actual model object and doesn't load all the data. However, pluck is going to build an array of records with name "Tom", whereas the original statement only ever returns a single object or nil - so this technique could potentially be worse depending on the where statement. I'd like to avoid the array creation and potential for having a very long list of ids returned from the server. I could add a limit(1) in the chain,
Person.where(name: "Tom").limit(1).pluck(:id).first
but is seems like I'm making this more complicated than it should be.
With Rails 6 you can use the new pick method:
Person.where(name: 'Tom').pick(:id)
This is a little verbose, but you can use select_value from the ActiveRecord connection like this:
Person.connection.select_value(Person.select(:id).where(name: 'Tom').limit(1))
This might work depending on what you're looking for.
Person.where(name: "Tom").minimum(:id)
Person.where(name: "Tom").maximum(:id)
These will sort by id value while the Person.where(name: "Tom").first.id will sort off of your default sort. Which could be id, created_at, or primary_key.
eitherway test and see if it works for you
Good Morning,
why there are two methods, who returning the almost the same result.
I know "only", that the method Method.fetch() returns a promise.
What is the main difference between this two methods?
They return different results :) fetch returns a promise (as you said) immediately, which upon resolution will be your record. find returns a record immediately (possibly empty). If the record already exists client side then it will return that record, if it doesn't, it's an empty record, and once ember model finishes fetching the data it will populate the record with it's properties. They both have their pros/cons. fetch is safer for async programming if you depend on the record being populated before using it. find is convenient for immediate response time, with delayed population. Click run inside the examples a few times to view the differences.
Find
http://jsbin.com/UXOtOJI/20/edit
Fetch
http://jsbin.com/porozuno/1/edit