如何在coredata中创建数据库视图

Question

I have quite a few fields in an entity in core data (say the entity is called Address) such as street, number, city, and state. I want the user to input a text string such that the app will search the entity Address for records which matches. How should I do this?

I basically want to have a generated field (search field) which will be "number, street, city, state" and try to find a record such that this search field contains the input string. I want this field to automatically updates itself when any field it contains (eg, "number", "street", "city", "state") changes.

I was looking around on Google and found the database view thing ( https://en.wikipedia.org/wiki/View_(SQL) ) which seems promising. But I cannot find any information on how to create a database view in core data. Anybody can point me a direction? Thanks!

Answer 1

I don't understand some parts of your questions, but my initial thoughts:

I have quite a few fields in an entity in core data (say the entity is called Address) such as street, number, city, and state. I want the user to input a text string such that the app will search the entity Address for records which matches. How should I do this?

I basically want to have a generated field (search field) which will be "number, street, city, state" and try to find a record such that this search field contains the input string. I want this field to automatically updates itself when any field it contains (eg, "number", "street", "city", "state") changes.

Assign your controller (or another object) as a delegate to the UITextField. Override the most appropriate delegate method and then perform a fetch query on the Core Data model with the entered string. Update your view in the callback with the top most result.

I was looking around on Google and found the SQL view thing which seems promising. But I cannot find any information on how to create a database view in core data. Anybody can point me a direction? Thanks!

A SQL View? Are you talking about a database browser? DB Browser Lite has always done the job for me - it allows you to browse the schema, the data and perform SQL queries. Print out to the console the location of the model, and then use the OS File Browser to navigate to that location.

In Objective-C, that console print out would look something like:

     - (NSURL *)applicationDocumentsDirectory {
        return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
    }

Xcode doesn't have a DB viewer per say. As you probably know, you can easily edit the entities and their attritibutes in the Table View when you have the .xccdatamodelId file selected. From that file, you can inspect the entire model and its relationships in the Graph View, almost like a UML snapshot.

Answer 2

You could create a computed property in your Address class and use it for your search. It will update if you change any of the attributes it uses.

var fullAddress: String {
    return "\(number) \(street) \(city ?? "") \(state ?? "")"
}

(Here I assumed city and state are optional attributes)

Regarding a Db view, Core Data is an ORM and not a SQL database so there is no such thing as a view.