I am new to Core Data, and am designing a schema. I would like to to comment things like:
This what the field name means, and this is what it should contain
Here is why we have this relationship
This integer corresponds to this enum
this field is in this encoding, or can only contain [a-zA-Z0-9-]
I've read over the Xcode Entity Modeling Tools for Core Data articles, and it appears that you can not add any sort of comments, either to the diagram or on a per-attribute basis. How do you document your schema?
Unfortunately, there is no equivalent of annotations on the xcdatamodel document or comment fields associated with entities/attributes/relationships. In our shop, we have a separate document (an outliner works well) for annotating/commenting on xcdatamodels. Descriptive attribute/relationship names often goes a long way just on its own.
In terms of documenting constraints (e.g. "this field can only contain [a-zA-Z0-9-]"), that can be encoded in validation methods for the custom objects associated with an entity.
Related
Disclaimer: Please do not suggest database-model redesigns / database model concept flaws. This question is about the case described, there is no way to change that case apprently.
Assuming i hava a table fruits, with name, color and type as fields
This means, all apples have the type=apple, all oranges have type=orange and so on.
Now creating a JPA entity/model called Apple with those 3 fields mapped and the Table=fruits, i want to create a AppleRepository where the argument type is statically set to apple and not visible to the outer consumers.
So i do not want to offer
AppleRepository.findByTypeAndNameContains with requiring the caller to now to set type to apple
but rather just
AppleRepository.findByNameContains while type is statically set to apple.
(With the same method i would then chose to Orange and the OrangeRepository using type=orange)
I understand i could use #Query to write a custom query where type is just statically included and only mapping the dynamic parameters... but
Question:
Is there a elegant way to implement that without using #Query?
What you have is the principle behind the "singe table" inheritance strategy. It consists in storing all the entities in a hierarchy inside a single table, and distinguishing them using a discriminator column (i.e. your type column).
See the documentation for details
I am evaluating HippoCMS and am trying to model a schema of Venues. I want to model a document that has non-translatable features such as telephoneNumber and emailAddress, plus translatable features such as description.
How do I model this in HippoCMS? How do I ensure that the non-translated fields are shared between the different translations, to avoid each translated document having its own copy of a value. Obviously no matter which language you are reading a site in, the telephoneNumber shouldn't change.
The only way I have found for the moment is to create a document called Venue and another document called VenueTranslation. Venue would contain the telephoneNumber and VenueTranslation would contain its description and a link back to the Venue document. There would then be VenueTranslation documents for each language.
Is this the correct approach?
That could work, but you will run into usability issues. I'd say it depends on how many venues you plan to enter into the system, how many languages you are targeting, and, in the end, how keen are your CMS users to pick the right Venue document for every VenueTranslation corresponding to a language. I can see how this will quickly become error prone and cumbersome, but I don't have the numbers.
Regarding the final question, it's not correct nor incorrect: it's just that since the granularity of the translations in Hippo is at the document level and not at the field level, you have to do it this way. Your model makes sense but is not well supported in the CMS. This use case is trivial in a CMS that supports the notion of translatable field.
I'm currently developing my first MVC component for Joomla 3.x. All in all I'm bit struggling with language/translation issues in database.
My problem is that I need to store translated content of user generated content which comes from the backend. For example someone enters a new item in German (stored in database) and needs a translation in another language. How to accomplish that in Joomla? I don't like to generate a new item for every different language when the rest is all the same.
I thought about a table "item" and a table "item_language" with that structure (strongly simplified for viewing purposes):
item
id PRIMARY INT
price DOUBLE(4,2)
item_language
itemid PRIMARY INT
language PRIMARY CHAR(5)
name VARCHAR(50)
In item_language I would like to store the different translated versions. In the language field there would be the region code (eg. de-DE) to identify the language.
My problems:
How to display the different (translated) versions in backend?
Is this the right database model?
Any help is appreciated!
You have really found yourself a nice task for a first component in Joomla!
A rather generalist answer:
The database model seems right. Alternatively you could encode in JSON the language data, but this could make later query operations potentially difficult. This way you will only have one table to work with.
As far as I know (if you are using JModel / JTable to manipulate the data) can't do this directly, as JTable is really only designed to manipulate single tables.
What you can do:
For editing: figure a way to represent this graphically ( for your users to see and edit this one to many relationship) and to post this data (language texts as an array) to JModel. In the model you can maintain the desired relationships and save the data using JTable.
Viewing (without editing) shouldn't be an issue, it would be a simple JOIN.
If you are willing to create a basic component on github, I might even give you a hand with JModel / JTable.
I found a way to deal with the things I needed.
Thanks Valentin Despa for guiding me in the right direction :-).
Here the whole procedure (simplified - validations and exact steps omitted):
Define the form fields in the models/forms/site.xml as normal.
In views/site/tmpl/edit.php add self coded Javascript (based on jQuery) to deal with the fields which have content in multiple languages stored as JSON in database.
Clone the original form element and modify the needed attributes (id, name, ...) to display a special version just for the defined languages. As content - extract the JSON for the needed language from original field content and display.
Hide the original field with Javascript and append the customized versions to DOM.
Afterwards in tables/site.php I read the dynamically generated content withJInput and build together the original field by generating JSON and saving to database.
It's working like expected.
I'm about to embark on a project where a user will be able to create their own custom fields. MY QUESTION - what's the best approach for something like this?
Use case: we have medical records with attributes like first_name, last_name etc... However we also want a user to be able to log into their account and create custom fields. For instance they may want to create a field called 'second_phone' etc... They will then map their CRM to their fields within this app so they can import their data.
I'm thinking on creating tables like 'field_sets (has_many fields)', 'fields', 'field_values' etc...
This seems like it would be somewhat common hence why I thought I would first ask for opinions and/or existing examples.
This is where some modern schemaless databases can help you. My favourite is MongoDB. In short: you take whatever data you have and stuff a document with it. No hard thinking required.
If, however, you are in relational land, EAV is one of classic approaches.
I have also seen people do these things:
predefine some "optional" fields in the schema and use them if necessary.
serialize this optional data to string (using JSON, for example) and write it to text blob.
I am currently working on a project where we are rewriting software that was originally written in Visual DataFlex and we are changing it to use SQL and rewriting it into a C# client program and a C#/ASP.Net website. The current database for this is really horrible and has just had columns added to table or pipe(|) characters stuck between the cell values when they needed to add new fields. So we have things like a person table with over 200 columns because stuff like 6 lots of (addressline1, addressline2, town, city, country, postcode) columns for storing different addresses (home/postal/accountPostal/ect...).
What we would like to do is restructure the database, but we also need to keep using the current structure so that the original software can still work as well. What I would like to know is would it be possible using Linq to write a DataContext Object Model Class that could sort of interpret the data base structures so that we could continue to use the current database structure, but to the code it could look like we where using the new structure, and then once different modules of the software are rewritten we could change the object model to use the correct data structure???
First of all, since you mention the DataContext I think you're looking at Linq to SQL? I would advice to use the Entity Framework. The Entity Framework has more advanced modeling capabilities that you can use in a scenario as yours. It has the ability to construct for example a type from multiple tables, use inheritance or complex types.
The Entity Framework creates a model for you that consists of three parts.
SSDL which stores how your database looks.
CSDL which stores your model (your objects and the relationships between them)
MSL which tells the Entity Framework how to map from your objects to the database structure.
Using this you can have a legacy database and map this to a Domain Model that's more suited to your needs.
The Entity Framework has the ability to create a starting model from your database (where all tables, columns and associations are mapped) en then you can begin restructuring this model.
These classes are generated as partial so you could extend them by for exampling splitting the database piped fields into separate properties.
Have you also thought about using Views? If possible you could at views to your database that give you a nicer dataschema to work with and then base your model on the views in combination with stored procedures.
Hope this gives you any ideas.