I currently have three models, Model, Manufacturer, and Device: A Model belongs to a Manufacturer, and a Device belongs to a Model. However, when I list the devices, I'd also like an entry for the manufacturer. I know I can fetch it easily with model.model.manufacturer.name, however, I'd like Device to have it's own manufacturer property. I have looked into Ember's computed properties, however, I can't seem to find a way to compute the model's manufacturer as the device's property, e.g.:
manufacturer: Ember.computed('manufacturer', function () {
return this.belongsTo('model').manufacturer
})
That's what I'm aiming for, but it doesn't work. Is this even possible at all?
Thank you!
You need to define like this :
manufacturer: Ember.computed.alias('model.manufacturer')
and if you don't want to set manufacturer in Device model, so use oneWay instead alias
Related
I have a QAbstractListModel that has a bunch of custom objects stored in it, and you can access the different fields of the custom objects in the model by specifying a role (if this is an improper use of Qt roles let me know because I must be confused). I want to display this data in a user friendly QTableView. I can get things displaying using a proxy model, but the issue is I don't want to display the raw values, I want to display specific data derived from the raw data. So for instance, I don't want a column for both ItemA.foo and ItemA.bar, I want to display just ItemA.foo - ItemA.bar in a single column. And to add to that, I want the automatic update functionality you get with models where if either ItemA.foo or ItemA.bar change, I want the difference column to automatically update and recalculate.
I would think that the way to do this would be to use some kind of table proxy model that listens to the source model, and then populates its own fields with the values derived from the source model and listens for dataChanged() signals from the source model. Then you plug this proxy model in to a QTableView. But to me this sounds like something that should be done in a view. Or is this something that should be done by the delegate? I could even go so far as to do these calculations in the base model itself and add roles specific to these values that should be displayed in the table, but that sounds like I am really overloading the responsibilities of the model.
TLDR: How do you manipulate data from a model in a QTableView? Should I do the data manipulation in the base model and then send that to the QTableView? Should I use a proxy model that manipulates the base data and sends it to the QTableView? Or am I completely misunderstanding something?
and you can access the different fields of the custom objects in the model by specifying a role
If you look at the documentation for Qt::ItemDataRole, you would see that Qt models should indeed provide different data for different roles but each role means some distinguished purpose of the data corresponding to the role. For example, the most commonly used role is probably Qt::DisplayRole as the data for this role defines the content displayed in the view e.g. it's the text in the table cell. If you are satisfied with all the other aspects of the view - font, background etc - you can just return empty QVariant for corresponding roles from your model, the view would figure out these details on its own. If you are using roles as a substitute for columns i.e. to return different pieces of conceptually the same data item, it is probably not the intended use of roles.
For the other part of your question - you can customize the appearance of data displayed in the view through the use of a delegate. For example, you could subclass QStyledItemDelegate, override its displayText method to display ItemA.foo - ItemA.bar instead of just ItemA.foo and then set this delegate into the column of your view corresponding to ItemA.foo via setItemDelegateForColumn. The tricky part here would be to detect changes in both ItemA.foo and ItemA.bar columns which would affect the text displayed in the delegate. A while back I implemented a dedicated class in one of my projects which listens to changes in some column of the original model and "reroutes" the change into another column through signal emitting. I did it to solve this very issue - to catch changes in what delegate should display although technically another model column is affected into which the delegate is not set.
I'm working on an e-commerce platform build using Django and Postgresql. In my platform I have an entity called "Category" and an entity called "Attribute". A category can have multiple attributes, but an attribute can only belong to one category.
For example, the "digital camera" category can have lens, image quality, etc. as its attributes.
I have come to realize that some attributes can belong to all categories. For example: packaging, shipping, customer service, etc.
In addition to these general attributes, in the future I may end up having attributes that belong to multiple categories. For example battery can belong to all categories in the Electronics department (categories belong to a department). But I'm not sure if this is a good idea as it may make things unnecessarily complex.
What's the best way to approach this? Please note that I need to be able to query the general attributes often. I have thought of the following solutions:
Make a default category and assign those attributes to that category. In the code write a special logic that will always look at these categories.
Allow a nullable foreign key in the attributes table. So an attribute can belong to no specific category indicating that it belongs to all categories.
Make another table for general attributes.
Store the category-attribute relationship in a third table. But then my question is how can I query for attributes that don't belong to any specific category?
I appreciate your help in advance.
UPDATE:
Not sure if this is the best solution, but I took the easy route and ended up making nullable m2m relationship between attribute and the other models. Thank you all for your help.
I like to develop a shopping cart website with multiple products.
(ex.: mobile phone, furniture etc.,)
here mobile phone specification will cover
size of display
memory
operating system
camera etc.,
but for furniture - its specification is entirely different from above electronic product.
type of wood
color
weight
shape
glass or mat finish etc.,
My question is: how to handle a common database-table for product specification ?
each & every category of product & its spec will be differ - so how to have a common
table ProductSpecificationTable ?
I searched many site including google.. but cant able to get the perfect soultion.
Please help me to move to next step.
Ask yourself the question: How can I accomplish this kind of database? First of all you need products.. Every product has to be in some kind of category and every category has to have his own properties. So, you've to create a product table with unique id and every product needs a category id. At this moment it is time to link from your property table to your category table(by id) and to set the values you need a 'property_value' table.
**table:** **id**
product --> category id
property --> category_id
property_value --> property_id
I hope you will understand my explanation otherwise just ask :)
You can add 1 more table to accomplish that. Table that contains cat_id, product_id and the property. That is a many to many relationship. I believe this way you can accomplish thst.
You can achieve this with a single table within a database but that will complicate the CRUD operations over the table. So I will recommend you to create one database like ‘Inventory’ which can have multiple tables (one table for each of the Product Type).
First Table could be list of Product Types you have (mobile phones, accessories, furniture):
You can use this table to populate your list of items available. Here the column _table_name will contain the actual name of the Tables.
Then for each of the product you can have different tables with different number of columns:
Table for Product Type Mobile Phones:
Table for Product Type Furniture:
I hope this will help.
I'm looking for an idiomatic way to write an "active record" like method to filter out inactive models
Using the latest ember-data I usually pull in all employee records like so
var employees = this.store.all('employee');
Keep in mind that I'm doing this "filter" 100% client side because I have everything in memory. I use all the employees for a few parts of the app and need the "all" like behavior in these situations. But as I'm also allowing "active/ inactive" status I'd like to filter them down client side for a few features.
I wanted a nice way to query this using a simple filter and I thought it would be active-record like to extend the model and add this but I wanted some guidance first (ie- should I be doing this when the store is not injected into the model directly, and if yes how should I go about injecting this?)
If I shouldn't do this, what is the best way to get all employees and filter down to get only the active ones? (ie- can I just invoke store.all and apply the filter or do I need to work with this data differently) ?
(here is a sample of the filter I'm doing manually now)
return content.filter(function(apt) {
return apt.get('employee').get('active') === true;
});
Ember Data's store has a filter method that has the same functionality as the all filter, aka live record array.
store.filter('employee', function(employee){
return employee.get('active');
});
I'm currently implementing a solution using django admin, it allows users to define in the db a product, and then custom attributes and details, more details may be aggregated by a common attribute, this allows me to query with ajax a custom view that returns some JSON data to build automagically the form fields that I need directly in the same formset view (manipulating the DOM).
The current DB design follows this schema:
Catalog(name, description, photo)
Product(rel_catalog, name, base_price, photo, manufacturer_email)
ProductDetail(rel_product, rel_attribute, percentage_price, fixed_price)
ProductAttribute(rel_product, name, description)
As you may see I have a catalog, where there can be more products, a lot of details per product, aggregated by attributes. Then I simple show by default the Catalog, then the select with all available products for that catalog, then, choosing the right Product, I obtain the complete form (each row has a label with ProductAttribute.name and a select with related ProductDetail).
All works pretty dam good, but I also need to store this references in the DB when someone completes the form (making an order with choosen products). This forms are displayed as StackedInline (the ModelAdmin is for the Order).
I don't know how many options there may be per product so I was thinking to use this design to track orders:
Order(customer, status, notes, tot_price, inserted_by)
OrderItem(rel_order, catalog, product, unit_price)
But I don't know how to store the dynamic added inputs...
I was thiking to implement OrderItemProperty(rel_orderitem, rel_productdetail, rel_productattribute) to store each single input... but how do I loop over this unknown fields?
Maybe do you suggest a better design?
If you need more code just ask for it and I'll reply with a pastebin link.
Thankyou.
Finally I got a working solution,
I've created a custom view, overriding the default "add/" view, this way I can customize whatever I want to and I can read the POST data handling each validation, putting then the data in the right model.