I am making a ZF2 app. I am using entities, mappers and services (e.g. UserEntity, UserMapper, UserService) to manage the objects/models. Properties in the entities are CamalCased (e.g. FirstName, LastName) while in the database, fields are using underscore (first_name, last_name). I will plan to use a hydrator to map the properties and db-fields when retrieving or saving. The service object (UserService) will be used to communicate with the mapper to retrieve and save data models using the mapper. The hydrator will convert the result of mapper and convert them into proper entities.
The thing I am confused is that when the service (UserService) need to provide some cirteria - for example to find all users with a specific 'last name', will the service use the database field names (last_name) or entity properties name (LastName)?
If the db field name is used in the Service, so any change in the db structure will require me to update the service also, which completely fails the reason of using the whole approach.
If you take a look at the ClassMethods:hydrate method (https://github.com/zendframework/zf2/blob/master/library/Zend/Stdlib/Hydrator/ClassMethods.php) you will see that it just copies the properties from one object to another. You have the option of converting the property names to/from camelCase but that's it.
If you change a column name in your database then you will need to change corresponding property name in your object. And vice versa. Which I believe is the crux of your question?
If you want to make table column names be independent of your method names then you need something that lets you define an actual mapping table somewhere. Change a column or method name and you only need to update the configuration mapping table.
Not a ZF2 expert so I could be wrong but it doesn't look like any of the supplied hydrators support this.
I do know that Doctrine 2 supports it.
Related
I want to know the best way of avoiding entity duplication in an ASP.NET Core Web API project.
Imagine that you have a product with a name and manufacturer and you want to make sure if the name is not duplicated. Imagine that a new product with a name came from client (dto) and we need to look if the name (entity) already exists in the database (using EF).
You need to trim the name (name.trim()) for both names from entity and dto
You need to remove all the whitespaces in between (string.replace(" ", string.empty())
You need to change everything to lower case (string.lower())
Finally you need to compare these two
Is there any best practices how to do this without writing all the code? I tried to use string.compare with the compareoptions like ignorecase and ignoresymbols and also the string.equal() with ignorecase option but the EF gives me an alarm that it can not translate the code.
br
I have a suggestion for your approach.
Introduce another column (This can be a primary key with other keys) and save the name with trimming and lowercase when you insert a new record to that table.
Example:
Original Name : Amir Masoud Babaei -->
New Column value: amirmasoudbabaei
And when you insert a new record, do your trimming and lowercase changes and save it to the database. Since it is a primary key, it should throw an error.
So with this approach, you don't need to loop through all the names and validate if the name is already exist.
Say my object has a Name field, and I wish to split it into FirstName and LastName fields. Or maybe it has an address string and I'm adding Lat and Lng fields that require geocoding. Etc etc.
I expected to have access to my DbContext in the Up() and Down() methods, but all I've been able to find (besides the builtin functions) is the .Sql() call. This is enough for adding and removing columns, but not for transforming existing data into new formats.
Is it safe to reference my DbContext inside an Up() invocation? Or is there another recommended pattern for implement migrations that require more than trivial SQL?
No you cannot use DbContext inside Up method because it already refers new model but your database still targets the old model.
Edit:
All data migrations must be done through Sql. You can for example create temporary table, move old data to temporary table, use migration of table structure and move data from temporary table back to the original with using some transformation directly in SQL - splitting varchar values should not be a big deal.
Rather than trying to split the Name into two different fields, rethink your migration. Sometimes it might be best staged. I can think of two ways to perform your transformation.
Migration path #1: New Fields, then Delete old
Create migration for new field for FirstName and LastName, and in the Up() method, you still have the Name field, split it, insert into First and Last fields.
Create another migration to remove the old Name field.
Migration path #2: Repurpose and Rename
Create a migration adding the LastName field, and renaming Name to FirstName, move the last name data, modify the renamed First/Name field to only hold the first name.
Both paths have advantages and disadvantages. And regardless of the complexity of your transformation, you should be able to break it out into logical stages to accomplish the goal.
I want to use a Money value object in my application. I have found several examples of a Money datatype. But I can't figure out how to use them with EF4. I would like to store each amount as a Decimal/CurrencyCode pair (where currencycode is a string - "USD", "SEK", etc) in the database. I tried creating a complexType but I couldn't get that to work. Is this possible?
It should be definitely possible. Your complex type is just pair of decimal and string property. It is exactly what complex type are used for. Depending on your approach you must do:
Database first:
You will define your database first. Your table will contain money and varchar columns representing your new type. When you update your EDMX model from database it will include it as scalar properties to your entity. You must remove those properties. Then go to model browser and create new complex type. Return back to entity and add complex property of your new complex type. And at the end you must go to entity mapping and map your complex type to those database columns.
Here is basic tutorial from MSDN but from unknown reason they didn't include such elementary details like screenshots. Here is some video from channel9.
Model first:
This is similar to database first but you don't have to deal with database creation and mapping. It will be generated for you.
Code first (EF 4.1):
You must create separate class for your complex type and use it as property in your entity. You should not need to map it by default - mapping should be infered. If it doesn't work you can map complext type either by using ComplextTypeAttribute annotation or by defining mapping in DbModelBuilder.
I can further extend approach you need to use if you provide more details.
We've started using Entity Framework 4 for data access and have come across an issue or perhaps lack of understanding.
Our current system is heavily reliant on Stored Procedures, these procedure contain some necessary business logic so we need to continue to use these when doing Select/Insert/Update/Delete.
The issue we are having is the following:
We've mapped a table to an entity, let's say for example this is a User entity and has the following properties - UserId, FirstName, LastName
Now in our sproc to insert a user we accept FirstName, LastName, CreatedById as parameters.
As our User Entity has no CreatedById we get an error indicating that no property of our Entity can be mapped to the "CreatedById" parameter.
Now one thing we've tried is to manually add a CreatedById scalar property to our Entity, but this results in the issue that there is no Field in our User table in the data source that maps to CreatedById. In general the additional property that we'd like to pass in is not something that is stored.
Now there is potential solution to this in that we can just map the procedures to Function Imports and not bother with using the .AddObject, .DeleteObject, .SaveChanges way of manipulating our objects but that doesn't feel like the way to go about it.
that's a good question. There are few options i can tell u.
instead of mapping the entity to the table, map it a view and have the view return CreatedById and then your problem would be solved.
Second option is to create overloaded stored procedure that takes only FirstName, LastName and calls the actual stored procedure with a default value for CreatedById. You can create overloads at the database layer or create it in the model in the ssdl layer which supports inline stored procedure.
exec myproc #firstName,#LastName,null
I'm just starting out with the Entity Framework and ADO.NET Data Services and I've run into an issue that I can't seem to figure out. I have two tables, one that has user information and the other that has a created by field. Within the database, there isn't a foreign key between these tables. The user table contains an arbitrary Id, a username, and a display name. The created by field contains the user's username. In my entity I would like to have the user's display name since this is what I need to display and expose over the ADO.NET Data Service? I'm aware that I could restructure the database, but I was hoping that I could do the join using the username as I would in a SQL statement.
Thanks in advance,
-Damien
You can make a view using a join of both tables, and then use this object to display the user's name.
There's some info on mapping custom queries here.