how do I serialise NSDictionary from a Class - Swi

Question

in Objective-C, I am using following codes to serialise a custom class to a dictionary which working fine. In order to being familiar to Swift, porting Objective-C codes to Swift. However I couldn’t achieve this one, how do I make this with Swift?

this is how I achieve with Objective-C

.h
#import <Foundation/Foundation.h>
#import <objc/runtime.h>

@interface NSObject (aClass_NSDictionary)
- (NSDictionary *)NSDictionaryFromClass;
@end

.m
@implementation NSObject (aClass_NSDictionary)

- (NSDictionary *)NSDictionaryFromClass {

    Class aClass = [self class];
    u_int propertiesCount;

    objc_property_t *propertiesInAClass = class_copyPropertyList(aClass, &propertiesCount);

    NSMutableDictionary *propertiesDictionary = [[NSMutableDictionary alloc] initWithCapacity:propertiesCount];

    for (int i = 0; i < propertiesCount; i++)
    {
        NSString *strAKey = [NSString stringWithCString:property_getName(propertiesInAClass[i])
                                               encoding:NSUTF8StringEncoding];

        [propertiesDictionary setValue:[self valueForKey:strAKey]
                                forKey:strAKey];
    }
    free(propertiesInAClass);
    return propertiesDictionary;
}
@end

when I wrote same code in swift i couldn’t manage to find out equivalent of [self class].

class class2dicti : NSObject {

    class func nsdictionaryFromAClass() -> NSDictionary {

        let aClass = self.classForCoder
        var propertiesCount : u_int
        let propertiesInAClass : objc_property_t = class_copyPropertyList(aClass, &propertiesCount)

        //return NSDictionary()
    }
}

Update

so far i have tried:

    let aClass = self.classForCoder
    var propertiesCount : u_int
    let propertiesInAClass : objc_property_t = class_copyPropertyList(aClass, &propertiesCount)

and

let aClass : AnyClass! = self.classForCoder()

no success, still same compiler error "Could not find an overload for '__conversion' that accepts the supplied arguments"

Solution

regarding to answers below I found this solution and it worked. Basically I have created extension for my class.

class myClass : NSObject {
    var propertyOne = "prop One"
    var propertyTwo = [1, 2, 3]
    var propertyThree = ["A":1, "B":2, "C":3]
}

extension myClass {
    func toDictionary() -> NSDictionary {

        var aClass : AnyClass? = self.dynamicType
        var propertiesCount : CUnsignedInt = 0
        let propertiesInAClass : UnsafePointer<objc_property_t> = class_copyPropertyList(aClass, &propertiesCount)

        var propertiesDictionary : NSMutableDictionary = NSMutableDictionary()

        for var i = 0; i < Int(propertiesCount); i++ {
            var strKey : NSString? = NSString(CString: property_getName(propertiesInAClass[i]), encoding: NSUTF8StringEncoding)
            propertiesDictionary.setValue(self.valueForKey(strKey), forKey: strKey)
        }
        return propertiesDictionary
    }
}

now this let myclazz = myClass().toDictionary() gives me the NSDictionary. all suggestions are welcome.

Answer 1

I'm using this way archiving anything which conforms the NSCoding protocol.

first I get the URL for the folder, like e.g. Documents folder:

var error: NSError?
let documentURL : NSURL = NSFileManager.defaultManager().URLForDirectory(NSSearchPathDirectory.DocumentDirectory, inDomain: NSSearchPathDomainMask.UserDomainMask, appropriateForURL: nil, create: true, error: &error)

---

then I archive it into that folder:

let object: AnyObject = // ...
let filename: String = "<filename>"
let customExtension: String = "<extension>"
let urlForFile: NSURL = documentURL.URLByAppendingPathComponent(filename).URLByAppendingPathExtension(customExtension)
let result: Bool = NSKeyedArchiver.archivedDataWithRootObject(object).writeToURL(urlForFile, atomically: true)

---

and unarchiving later is quite similar to the recent way:

let data: NSData = NSData.dataWithContentsOfFile(urlForFile.path, options: NSDataReadingOptions.DataReadingUncached, error: &error)
let object: AnyObject = NSKeyedUnarchiver.unarchiveObjectWithData(data)

---

NOTE: that is a raw example, without checking anything whether or not it is nil or handling the possible error. you may need to add those for your final code.

Answer 2

This is how I implemented deep serialization.

If property is DictionarySerializedObject then it's recursively serialized.

Be careful because class_copyPropertyList() does not return properties of optional Swift types like Bool?, [String?] because Foundation does not provide bridges for them. For example it provides bridge for Bool to NSNumber but does not provide bridge for Bool?.

import Foundation

protocol DictionarySerializable {
    func serializeToDictionary() -> [String:AnyObject]
}

class DictionarySerializableObject: NSObject {
}

extension NSObject: DictionarySerializable {
    func serializeToDictionary() -> [String:AnyObject] {
        var aClass: AnyClass? = self.dynamicType
        var propertiesCount: CUnsignedInt = 0
        let properties = class_copyPropertyList(aClass, &propertiesCount)
        var dictionary = [String: AnyObject]()
        for var i = 0; i < Int(propertiesCount); i++ {
            if let name = NSString(CString: property_getName(properties[i]), encoding: NSUTF8StringEncoding) as? String {
                dictionary[name] = getDictionaryValueForObject(self.valueForKey(name))
            }
        }
        free(properties)
        return dictionary
    }

    private func getDictionaryValueForObject(object: AnyObject?) -> AnyObject {
        if let object: AnyObject = object {
            if let object = object as? DictionarySerializableObject {
                return object.serializeToDictionary()
            } else if let object = object as? [AnyObject] {
                var array = [AnyObject]()
                for item in object {
                    array.append(getDictionaryValueForObject(item))
                }
                return array
            } else if let object = object as? NSData {
                return object.base64EncodedStringWithOptions(NSDataBase64EncodingOptions(0))
            } else {
                return object
            }
        } else {
            return NSNull()
        }
    }
}

Answer 3

In Swift you never work with classes. You work with types:

var clazz: AnyClass? = self.dynamicType
class_copyPropertyList(clazz, nil)

All Obj-C methods that return a Class, e.g. classForCoder are updated to return a Swift type instead (AnyClass).

Note that you have other type problems there:

var propertiesCount : CUnsignedInt = 0
let propertiesInAClass : UnsafePointer<objc_property_t> = class_copyPropertyList(clazz, &propertiesCount)

If you actually need to access the Obj-C class as AnyObject, for example to create an array of classes and pass it to Obj-C, see this

Answer 4

I have written an objective c library that automatically does this based on key values and property names. I have a branch to support Swift classes and it works well. https://github.com/aryaxt/OCMapper