I get an NSInferredMappingModelError when I try to migrate my model.
During the migration, the objects of an entity Example are migrated from having a to-many relationship to a to-one.
The migration fails with the error when it tries to make an NSMappingModel via inferredMappingModelForSourceModel.
I need to use custom migration because of the nature of the project - the program operates on (ideally) any kind of model.
Any ideas or nudges in the right direction?
Because lightweight migration cannot deal with the change you've made, inferredMappingModelForSourceModel is going to fail. You have to create the mapping yourself and load it with mappingModelFromBundles.
It is hard to go into a lot of details here without knowing more specifics but you can learn more about custom migration in Apple's Core Data Model Versioning and Data Migration Programming Guide. You might want to start by looking at the sections "Customizing the Migration Process" and "Mapping Overview".
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Need help! I am new to Core 2.0 and VS 2017 and haven't had much experience with MVC. I have an existing database that I need to use with a core 2.0 project at work. I was able to use the Scaffold-DbContect to initially create the domain models from the existing database.
However, the database developers are making changes to the database and adding new tables. I need to keep my domain models in sync with the database changes that are being made.
The only thing I can find on the internet is how to make changes to the model and update the database schema. However, I need to update the model from changes made to the database.
EF Core works on Code First approach. And You guys are following DB First approach together. So you should make changes in your code and then generate migrations accordingly, Otherwise, it will lead you in trouble.
You can use EF Core Power tool for generating the db changes at code side. But in this case you have to take care while generating migrations from code side.
My core data store in the previous version to my app is different to the current one in the following ways:
Attributes missing
New attributes
Attributes which need changing
New entities
New relationships
Attributes which need moving between entities
How should I go about migrating my data? What I had in mind before looking into this was that I could just write code that could take the data from the previous model and put it in place in the new model.
I think the Core Data Model Versioning and Data Migration Programming Guide will cover these issues in some detail.
I have the older version of the core data model of the released app. Now, in the next version of the app, I am migrating the core data model to new model. Is there a way to get the attribute values from the old model before actually migrating to the new version of the model or is there possibly a way to know if the migration is to be occurred.
When you migrate, Core Data actually moves existing values for you. If you're doing a relatively simple migration, such as adding or removing some properties, Core Data does its best to make the move as seamless as possible. In many cases, you won't need to make any changes other than set your new model. See my answer here for more.
Yes, it is possible.
To get the attribute values from the old model you'll need to create custom entity migration policies (NSEntityMigrationPolicy subclasses). Then in -createDestinationInstancesForSourceInstance:entityMapping:manager:error: you'll receive source instance, and it is completely up to you how to create destination instances from source instances.
There is a method to check if a given store is compatible with store coordinator model: -[NSManagedObjectModel isConfiguration:compatibleWithStoreMetadata:].
I've been working Entity Framework trying to get better with it. I'm liking what I'm seeing thus far but now have a question. With this new 'Code First' approach (from the CTP 4 download) we can now use EF from a code first approach, but I'm trying to find out if one can use an existing EDMX file with this approach.
I have a project I'm working on which has an EDMX file and I notice the ModelBuilder has a RegisterEdmx method but am not finding a lot out there on whether this will allow to use an existing EDMX file with my code first approach.
Also, I know with this new CTP things like RecreateDatabaseIfModelChanges are avilable but these options drop the database and recreate it, wont this cause all your data to be lost if you ever change your models? Is there something I'm missing here?
I can't speak to using previously generated EDMX files but there is support to use Code First with existing databases. As for the automatic Recreate, yes, this will kill all your data. This is meant only in rapid development where the persistence of data doesn't matter (and, in fact, is likely unwanted as you discover issues with business logic and want a clean start with your updates.)
This is meant only as a quick way to develop. As of (when Scott Guthrie blogged about the CTP - jump to section 5) there are no data migration features available. Your options are to manually update the database to match your model, delete the database and let it be recreated or set the automatic recreate option. Only the first option is non-destructive to your data.
I'm working on proof of concept application like crm and i need your some advice.
My application's data layer completely dynamic and run onto EF 3.5. When the user update the entity, change relation or add new column to the database, first i'm planning make for these with custom classes. After I rebuild my database model layer with new changes during the application runtime. And my model layer tie with tightly coupled to my project for easy reflecting model layer changes (It connected to my project via interfaces and loading onto to application domain in the runtime).
I need to create dynamic entities, create entity relations and modify them during the runtime after that i need to create change database script for updating database schema. I know ADO.NET team says "we will be able to provide this property in EF 4.0", but i don't need to wait for them.
How can i update database changes during the runtime via EF 3.5 ?
For example, i need to create new entity or need to change some entity schema, add new properties or change property types after than how can apply these changes on the physical database schema ?
Any ideas ?
This blog post may have what you need. It describes a way to capture the metadata of your model and modify it in-transit, during runtime. I haven't a clue how it works, but it sounds cool.
Changing Entity Framework storage DB schema during Runtime
http://blogs.microsoft.co.il/blogs/idof/archive/2008/08/22/change-entity-framework-storage-db-schema-in-runtime.aspx