ImportOperations.swift

    private var didBeginImport = false // This is a hack until I've figured out why completion block runs twice..
    private func createImportOperations(data: [String: AnyObject]) {
        guard !didBeginImport else { return }
        didBeginImport = true

        if let ingredients = data["ingredients"] as? [[String: AnyObject]] {
            ingredients.forEach {
                let op = IngredientOperation(data: $0, repository: repo, state: state)
                if let id = op.identifier {
                    state.ingredientOperations.updateValue(op, forKey: id)
                }
                operationQueue.addOperation(op)
            }
        }

        if let sources = data["sources"] as? [[String: AnyObject]] {
            sources.forEach {
                let op = SourceOperation(data: $0, repository: repo, state: state)
                if let id = op.identifier {
                    state.sourceOperations.updateValue(op, forKey: id)
                }
                operationQueue.addOperation(op)
            }
        }

        if let categories = data["categories"] as? [[String: AnyObject]] {
            categories.forEach {
                let op = CategoryOperation(data: $0, repository: repo, state: state)
                if let id = op.identifier {
                    state.categoryOperations.updateValue(op, forKey: id)
                }
                op.addDependencies(dependencies: state.sourceOperations(in: op.sourceDependencies))
                operationQueue.addOperation(op)
            }
        }

        if let recipes = data["recipes"] as? [[String: AnyObject]] {
            recipes.forEach {
                let op = RecipeOperation(data: $0, repository: repo, state: state)
                op.addDependencies(dependencies: state.sourceOperations(in: op.sourceDependencies))
                op.addDependencies(dependencies: state.categoryOperations(in: op.categoryDependencies))
                op.addDependencies(dependencies: state.ingredientOperations(in: op.ingredientDependencies))
                operationQueue.addOperation(op)
            }
        }
    }

ImportState.swift

final class ImportState {

    /// Pending and completed ingredient operations.
    var ingredientOperations: [String: IngredientOperation] = [:]

    /// Pending and completed source operations.
    var sourceOperations: [String: SourceOperation] = [:]

    /// Pending and completed category operations.
    var categoryOperations: [String: CategoryOperation] = [:]

    /// An array of errors that occured during import.
    var errors: [Error] = []

    func ingredientOperations(in ingredients: Set<String>) -> [IngredientOperation] {
        return ingredients.map { ingredientOperations[$0] }.flatMap { $0 }
    }

    func sourceOperations(in sources: Set<String>) -> [SourceOperation] {
        return sources.map { sourceOperations[$0] }.flatMap { $0 }
    }

    func categoryOperations(in categories: Set<String>) -> [CategoryOperation] {
        return categories.map { categoryOperations[$0] }.flatMap { $0 }
    }

}