Functional Nerdgasm in Swift

functional-nerdgasm.swift

typealias DistanceRange = (from: Double, to: Double) // meters
typealias WaterListResult = (water: Water, lodging: Lodging, distance: Double, price: Float?)
typealias LodgingAndDistance = (lodging: Lodging, distance: Double?)

extension Water {

    // Returns waters that are sorted by their nearest (nearest to `center`) lodging's distance to `center`.
    static func watersByProximity(distanceRange: DistanceRange, center: CLLocation) -> [WaterListResult] {
        return ModelsStorage.waters
            .flatMap { (water: Water) -> [WaterListResult] in // Map to water's lodgings combined with their distances to center
                if let lodgings = water.lodgings {
                    let lodgingAndDistance = lodgings
                        .map { return LodgingAndDistance($0, $0.coordinates?.distanceTo(center)) } // attach distances to lodgings
                        .filter { return $0.1 != nil } // filter those with non-nil distance
                        .map { (lD: LodgingAndDistance) -> LodgingAndDistance in // force-unwrap filtered non-nil distances
                            return LodgingAndDistance(lD.lodging, lD.distance!)
                        }
                        .filter { (lD: LodgingAndDistance) -> Bool in // filter those that are within distanceRange
                            return lD.distance >= distanceRange.from && lD.distance < distanceRange.to
                        }
                        .sort({ $0.distance < $1.distance }) // sort lodgings of this water by distance
                        .first // select only first lodging
                    
                    if let foundLodgingAndDistance = lodgingAndDistance {
                        return [WaterListResult(water: water, lodging: foundLodgingAndDistance.lodging, distance: foundLodgingAndDistance.distance!, price: nil)]
                    }
                }
                
                return [] // found no lodgings for this water
            }
            .sort({ $0.distance < $1.distance }) // sort ALL lodgings by their distance
    }
    
}

if the lodgings property of the Water struct is [Lodging] instead of [Lodging]? it gets down to:

extension Water {

    // Returns waters that are sorted by their nearest (nearest to `center`) lodging's distance to `center`.
    static func watersByProximity(distanceRange: DistanceRange, center: CLLocation) -> [WaterListResult] {
        return ModelsStorage.waters
            .flatMap { water -> [WaterListResult] in // Map to water's lodgings combined with their distances to center
                    let lodgingAndDistance = water.lodgings
                        .flatMap { LodgingAndDistance(lodging: $0, distance: $0.coordinates?.distanceTo(center)) } // attach distances to lodgings and filter out nils
                        .filter { $0.distance >= distanceRange.from && $0.distance < distanceRange.to } // filter those that are within distanceRange
                        .sort { $0.distance < $1.distance } // sort lodgings of this water by distance
                        .first // select only first lodging

                    return lodgingAndDistance.map { [WaterListResult(water: water, lodging: $0.lodging, distance: $0.distance, price: nil)] } ?? []
            }
            .sort { $0.distance < $1.distance } // sort ALL lodgings by their distance
    }
}

I'm not sure why you're getting the first lodgingAndDistance then mapping into into an array of WaterListResults, I'm assuming you don't actually want that. If you don't you can get it down to:

extension Water {
    // Returns waters that are sorted by their nearest (nearest to `center`) lodging's distance to `center`.
    static func watersByProximity(distanceRange: DistanceRange, center: CLLocation) -> [WaterListResult] {
        return ModelsStorage.waters
                .flatMap { water in
                    let results = water.lodgings
                                        .flatMap { LodgingAndDistance(lodging: $0, distance: $0.coordinates?.distanceTo(center)) } // attach distances to lodgings, filtering out nils
                                        .filter { $0.distance >= distanceRange.from && $0.distance < distanceRange.to } // filter those that are within distanceRange
                                        .sort { $0.distance < $1.distance } // sort lodgings of this water by distance
                                        .first // select only first lodging
                                        .map { WaterListResult(water: water, lodging: $0.lodging, distance: $0.distance, price: nil) }

                    return results
                }
                .sort { $0.distance < $1.distance } // sort ALL WaterListResults by their distance
    }
}

Have to assign the results thing because otherwise swift thinks the expression is too complex

another option is this;

extension Water {
    // Returns waters that are sorted by their nearest (nearest to `center`) lodging's distance to `center`.
    static func watersByProximity(distanceRange: DistanceRange, center: CLLocation) -> [WaterListResult] {
        let toResults = { water in
            return water.lodgings
                .flatMap { LodgingAndDistance(lodging: $0, distance: $0.coordinates?.distanceTo(center)) } // attach distances to lodgings, filtering out nils
                .filter { $0.distance >= distanceRange.from && $0.distance < distanceRange.to } // filter those that are within distanceRange
                .sort { $0.distance < $1.distance } // sort lodgings of this water by distance
                .first // select only first lodging
                .map { WaterListResult(water: water, lodging: $0.lodging, distance: $0.distance, price: nil) }
        }

        return ModelsStorage.waters.flatMap(toResults).sort { $0.distance < $1.distance } // sort ALL WaterListResults by their distance
    }
}