如何使用swift在IOS coredata中将MKPolyline属性存储为可转换的？

Question

允许在 CoreData 中快速存储 MKPolyline 所需的代码是什么？

例如，如果我有一个核心数据实体（例如“myEntity”），我想为其保存 MKPolyline，并将“折线”字段添加为可转换，并将其设置为“可转换”代码。也产生了 NSManagedObject 子类。

myEntity.swift

import UIKit
import CoreData
import MapKit
class myEntity: NSManagedObject {
}

myEntity+CoreDataProperties.swift

import Foundation
import CoreData
extension myEntity {
    @NSManaged var title: String
    @NSManaged var polyline: NSObject? 
}

问题 - 需要什么代码才能使其工作？

（我确实注意到这篇文章是objective-c，但是我很难理解/移植/让它工作-How do you store data from NSMutable Array in Core Data?）

Answer 1

归档折线对象并保存到Core Data：

    let context = self.fetchedResultsController.managedObjectContext
    let entity = self.fetchedResultsController.fetchRequest.entity!
    let newManagedObject = NSEntityDescription.insertNewObjectForEntityForName(entity.name!, inManagedObjectContext: context)
    let polylineObj = polyline() // For test purpose.
    let polylineData = polylineToArchive(polylineObj)
            newManagedObject.setValue(polylineData, forKey: "polyline")
        context.save()

从 NSManagedObject 中取消归档折线：

    let object = self.fetchedResultsController.objectAtIndexPath(indexPath) as! NSManagedObject
    let data = object.valueForKey("polyline") as! NSData
    let polyline = polylineUnarchive(data)
    log(polyline!)

MKPolyline 归档和取消归档功能。还有一些辅助函数。

func polylineUnarchive(polylineArchive: NSData) -> MKPolyline? {
    guard let data = NSKeyedUnarchiver.unarchiveObjectWithData(polylineArchive),
        let polyline = data as? [Dictionary<String, AnyObject>] else {
        return nil
    }
    var locations: [CLLocation] = []
    for item in polyline {
        if let latitude = item["latitude"]?.doubleValue,
            let longitude = item["longitude"]?.doubleValue {
            let location = CLLocation(latitude: latitude, longitude: longitude)
            locations.append(location)
        }
    }
    var coordinates = locations.map({(location: CLLocation) -> CLLocationCoordinate2D in return location.coordinate})
    let result = MKPolyline(coordinates: &coordinates, count: locations.count)
    return result
}

func polylineToArchive(polyline: MKPolyline) -> NSData {
    let coordsPointer = UnsafeMutablePointer<CLLocationCoordinate2D>.alloc(polyline.pointCount)
    polyline.getCoordinates(coordsPointer, range: NSMakeRange(0, polyline.pointCount))
    var coords: [Dictionary<String, AnyObject>] = []
    for i in 0..<polyline.pointCount {
        let latitude = NSNumber(double: coordsPointer[i].latitude)
        let longitude = NSNumber(double: coordsPointer[i].longitude)
        let coord = ["latitude" : latitude, "longitude" : longitude]
        coords.append(coord)
    }
    let polylineData = NSKeyedArchiver.archivedDataWithRootObject(coords)
    return polylineData
}

func polyline() -> MKPolyline {
    let locations = [CLLocation(latitude: 37.582691, longitude: 127.011186), CLLocation(latitude: 37.586112,longitude: 127.011047), CLLocation(latitude: 37.588212, longitude: 127.010438)]
    var coordinates = locations.map({(location: CLLocation) -> CLLocationCoordinate2D in return location.coordinate})
    let polyline = MKPolyline(coordinates: &coordinates, count: locations.count)
    return polyline
}

func log(polyline: MKPolyline) {
    let coordsPointer = UnsafeMutablePointer<CLLocationCoordinate2D>.alloc(polyline.pointCount)
    polyline.getCoordinates(coordsPointer, range: NSMakeRange(0, polyline.pointCount))
    var coords: [Dictionary<String, AnyObject>] = []
    for i in 0..<polyline.pointCount {
        let latitude = NSNumber(double: coordsPointer[i].latitude)
        let longitude = NSNumber(double: coordsPointer[i].longitude)
        let coord = ["latitude" : latitude, "longitude" : longitude]
        coords.append(coord)
    }
    print(coords)
}