Pass Array or FetchedResults as an argument to method-CodePudding

I have two identical methods that differ in the argument they receive. One receives an Array<Entity> and the other one a FetchedResults<Entity> object, where Entity is a CoreData Entity. It would be nice to simplify code by removing the duplication and only having one method.

    static func groupByDate(_ result : FetchedResults<Entity>)-> [[Entity]]{
        return  Dictionary(grouping: result){ $0.dateDescription }
            .values
            .map{$0}
            .sorted(by: { $0.first!.timestamp! > $1.first!.timestamp! })
    }
    
    static func groupByDate(_ result : [Entity])-> [[Entity]]{
        return  Dictionary(grouping: result){ $0.dateDescription }
            .values
            .map{$0}
            .sorted(by: { $0.first!.timestamp! > $1.first!.timestamp! })
    }

I tried to use a sequence of the Entity type to abstract the method because both Array<Entity> and FetchedRusults<Entity> adhere to the protocol. Unfortunately, I wasn't able to get it to work.

I'm curious how you would solve it.

CodePudding user response：

Both FetchedResults and Array conform to the Sequence protocol so you can use that as a generic type and have a where condition to only allow Sequence types that has Entity as it content

static func groupByDate<Values: Sequence>(_ result: Values) -> [[Entity]] where Values.Element == Entity {
    return Dictionary(grouping: result, by: { $0.dateDescription })
        .values
        .sorted(by: { $0.first!.timestamp! > $1.first!.timestamp! })
}