Have Record implement Decodable by default

[oddanderson]

In the guide for querying using Joins, the guide relies heavily on structs in favor of objects. When it comes to the filter/querying guide, this makes the examples really simple because struct implements decodable already, assuming you only have a limited set of property types.

However, if one of your object types in a struct is a Record, you need to implement Decodable'sinit(from: decoder) in both the struct AND the record object, such that I end up with:

struct EventInfo: Decodable, FetchableRecord {
    struct PartialContact: Decodable, FetchableRecord {
        var contactName: String
        var contactId: Int64
    }
    var event: Event
    var contact: PartialContact
    
    init(from decoder: Decoder) throws {
        event = try Event.init(from: decoder)
        contact = try PartialContact.init(from: decoder)
    }
}
class Event: Record, Decodable {
    
    private enum CodingKeys: String, CodingKey {
        case id
        ....
    }
    required init(from decoder:Decoder) throws {
        super.init()
        let values = try decoder.container(keyedBy: CodingKeys.self)
        id = try values.decode(Int64?.self, forKey: .id)
        ...
    }

As I was doing so, it seemed like I was writing a fair amount of duplicate code relative to the other functions I need to implement for Record, specifically enum Columns: String, ColumnExpression, required init(row: Row), and override func encode(to container: inout PersistenceContainer)

Curious if it makes sense to use those definitions to enable Record to implement Decodable for free

[groue]

Curious if it makes sense to use those definitions to enable Record to implement Decodable for free

It is not possible to have Record conform to Decodable without forcing all subclasses to conform to Decodable as well (even for people who don't care about Decodable). You can try in a fresh playground:

class Record: Decodable { }

// Compiler error: 'required' initializer 'init(from:)' must be provided by subclass of 'Record'
class MyRecord: Record {
    var id: Int64

    init(id: Int64) {
        self.id = id
    }
}