Repository impl helper(with Realm, Future)

Repository.swift

@_exported import class BrightFutures.Future
import func BrightFutures.future
import var BrightFutures.ImmediateOnMainExecutionContext
import RealmSwift

protocol RepositoryImplType {
    func runWrite(f: (Realm) throws -> Void) -> Future<Void, RepositoryError>
    func runRead<T>(f: (Realm) throws -> T) -> Future<T, RepositoryError>
    func runReadAndBlock<T>(f: (Realm) throws -> T) throws -> T
    func runWriteAndBlock(f: (Realm) throws -> Void) throws -> Void
}

extension RepositoryImplType {
    func runWrite(f: (Realm) throws -> Void) -> Future<Void, RepositoryError> {
        return future(context: RealmIOContext, task: {
            let realm = RealmInstanceManager.sharedManager.realm()
            do {
                realm.beginWrite()
                try f(realm)
                try realm.commitWrite()
                return .Success()
            } catch {
                realm.cancelWrite()
                return .Failure(.IOException(reason: "", error: error as NSError)) // TODO
            }
        }).map(ImmediateOnMainExecutionContext, f: { $0 })
    }
    
    func runRead<T>(f: (Realm) throws -> T) -> Future<T, RepositoryError> {
        return future(context: RealmIOContext, task: {
            let realm = RealmInstanceManager.sharedManager.realm()
            do {
                let res = try f(realm)
                return .Success(res)
            } catch {
                return .Failure(.IOException(reason: "", error: error as NSError)) // TODO
            }
        }).map(ImmediateOnMainExecutionContext, f: { $0 })
    }
    
    func runReadAndBlock<T>(f: (Realm) throws -> T) throws -> T {
        let realm = RealmInstanceManager.sharedManager.realm()
        return try f(realm)
    }
    
    func runWriteAndBlock(f: (Realm) throws -> Void) throws -> Void {
        let realm = RealmInstanceManager.sharedManager.realm()
        do {
            realm.beginWrite()
            try f(realm)
            try realm.commitWrite()
        } catch {
            realm.cancelWrite()
            throw RepositoryError.IOException(reason: "", error: error as NSError) // TODO
        }
    }
}