I have been reading the Ember documentation for v2.4, and I came across a part that I don't understand:
Some models may have properties that are deeply nested objects of readonly data. The naïve solution would be to define models for each nested object and use hasMany and belongsTo to recreate the nested relationship. However, since readonly data will never need to be updated and saved this often results in the creation of a great deal of code for very little benefit. An alternate approach is to define these relationships using an attribute with no transform (DS.attr()). This makes it easy to access readonly values in computed properties and templates without the overhead of defining extraneous models.
In my use case, I will only be displaying data, it will never be saved back to the server. Every example I have found for nested data, shows setting up separate models for each level of nesting, then setting up the relationships, as referred to as the "naive solution". So what would be the correct way to go about this? Can anyone please expand on this for me? Thanks in advance!
Looking at the comments, the answer would be:
Define the root object and define the fields of that object as DS.attr(). With no type information.
You will still be able to access the nested data using dot notation but you will not need to specify any more of the structure.
Have a look at the following link for a more complete look at this topic.
https://thejsguy.com/2016/01/29/working-with-nested-data-in-ember-data-models.html
Related
I'm trying to add Django to my react project. Currently, I'm stuck on defining correlating model fields in Django to what I had in React state.
This is what my old state looks like (when I stored all the info directly in the state
This is what my new state looks like (when I fetched the data from api and stored it into the state
This is the JSON file I'm using to load the data to django database
The reason I want to have "teamBackground", "textColor", "votedUpColor", "votedDownColor" properties is that I want to be able to style each team.
My question is how can I convert the values of these properties from string to object?
I tried defining these properties as CharField and JSONField, but they don't seem to be working. Is there any way to solve this problem?
Objects cannot be stored in a relational database AFAIK. You also dont need to store them. There are a few possible solutions to your problem.
You can create separate relations for teamBackground, textColor, votedDownColor, votedUpColor. All of these relations would have one column, 'color'. This may be the better solution if you plan to add more attributes to any of these classes. You would then have a one to one relationship between these relations and your original relation.
You can add them as columns in your current relation. While this is probably the most simple way to do it, its not scalable. If you need a different object for teamBackground, textColor, votedDownColor, votedUpColor, then you probably need a separate relation for them as well. However if you are looking for a hack, then you can just add their colors to your original relation instead of adding the object.
Again, kind of a hack but you can convert the objects to a JSON string, and then save that string as a column in your relation. Check here for more information about decoding and encoding JSON in python.
What is good practice for put data persisters in one place. For now i put model.save() in every controller when i save this object. But i think it is not good resolve, because it can make code duplicates.
I found in ember we have services https://guides.emberjs.com/v2.8.0/applications/services/, but according documentation it is place for not use data store.
My question is what is best practice for not duplicate data persist code?
Have you tried extending some base controller or maybe extending controllers with a mixin containing the actions and the logic? I think mixins would be the way to go for that.
I had problem with saving relation to object with same class as parent.
You can check this problem here.
When I read that I can easily set the relationship after the promise has fulfilled here I created another example with that info in mind. But it doesn't work as I expect.
What I expect
Create array of Box instances with relation to previous Box instance in each.
And the question is if I'm doing something wrong or it's a bug. Let me know if you need any informations.
Your example isn't clear and simple enough. It needs to be isolated to EXACTLY what you're having an issue about and nothing else.
Having said that, I have had quite a bit of success saving relations to objects with the same class as parent, and so I don't think this is a problem with Ember Data or Ember.
Your code is quite convoluted and uses the sync library, which I'm not faimilar with.
It's a good idea to things as simply as possible at first, so try creating a jsbin with just the isolated functionality relating to saving relations that you're attempting, and then adding additional layers of functionality and testing after each add.
I want to add a layout model to my website (a general settings file), and I want it to be available in the admin interface for configuration.
class Layout(...Model):
primary_header
logo_image
...
This structure shouldn't saved be in a table.
I am wondering if there is a built-in feature that can help me do this.
Thanks
My use case is a configurable layout of the website. Wordpress style. I would like to store that data in a concrete class, without having to implement the file /xml serialization myself.
What about an abstract model? It does not save in the database and is meant to be subclassed, but you are allowed to create instances of it and use its attributes. I assume you want some kind of temporary data structure to pass around that meets the requirements of a model instance.
class Layout(models.Model):
class Meta:
abstract = True
If you for some reason need actual concrete models, and are fine with it creating tables for them, you could technically also re-implement the save() method and make it no-op.
I don't really understand where and how you will be using this, but this is indeed a model that doesn't save.
Personally, I have actually used models that aren't intended to be saved, in a project that uses mongodb and the nonrel django fork. I create models that are purely meant to be embedded into other models as nested sub-documents and I never want them to be committed to a separate collection.
Update
Here is another suggestion that might make things a whole lot easier for your goal. Why not just use a normal django model, save it to the database like normal, and create a simple import/export function to save it out to XML or read into an instance from XML. That way you get 100% normal admin functionality, you can still query the database for the values, and the XML part is just a simple add-on. You can also use this to version up preferences and mark a certain one as active.
I've read the similar question on adding tags to a Django Blog model, where it mentions maintaining tags on the article as a StringList and a separate object to keep a count of these objects, which is good because I'd basically come up with the same idea myself, however I'm struggling to work how how to maintain the count.
I'm overriding the put() method of the main object, but how do I check to see if the tags have changed compared to the object currently stored? Is there any way to cheaply check the existing data without fetching a 2nd copy of the object?
One way to handle it is to store each object in memcache and only fetch the ones it doesn't find in there, but for a busy site, you're still going to be hitting the datastore quite often.
Check out taggable-mixin. It's a pretty straightforward way to add tags to any AppEngine model class as a mixin.