Re: Modify JSON in Swift
> On 7 Nov 2015, at 20:48, Roland King wrote: > > Quincey explained why it doesn’t work, value semantics run deep and > consistent in Swift. > > What you could do if you wanted, after messing with images, put it back into > the json dictionary again, after your for var image in .. code > > json[ “images” ] = images > > now you have modified json to have a new images member. oh not quite - you’re modifying images too - so you have to replace each image in that as well as you go. perhaps use one of the array operators which takes an array and returns a new array to get new images from old. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: Modify JSON in Swift
Quincey explained why it doesn’t work, value semantics run deep and consistent
in Swift.
What you could do if you wanted, after messing with images, put it back into
the json dictionary again, after your for var image in .. code
json[ “images” ] = images
now you have modified json to have a new images member.
> On 7 Nov 2015, at 14:54, Rick Mann wrote:
>
> I'm trying to do this, but I can't modify the JSON structure.
>
>
> ---
> import Foundation
>
> let s = "{ \"images\" : [ { \"thumb\" : \"url1\", \"width\" : 10 }, {
> \"thumb\" : \"url2\", \"width\" : 20 } ] }"
> let data = (s as NSString).dataUsingEncoding(NSUTF8StringEncoding)!
>
> do
> {
> if var json = try NSJSONSerialization.JSONObjectWithData(data, options:
> .MutableContainers) as? [String:AnyObject]
> {
> print("JSON: \(json)")
> if var images = json["images"] as? [[String:AnyObject]]
> {
> for var image in images
> {
> if let thumbURL = image["thumb"]
> {
> image["thumb"] = "FOOBAR: \(thumbURL)"
> print("new: \(image["thumb"])")
> }
> }
>
> let newData = try
> NSJSONSerialization.dataWithJSONObject(json, options:
> NSJSONWritingOptions(rawValue: 0))
> let s2 = NSString(data: newData, encoding:
> NSUTF8StringEncoding)
> print(s2)
> }
> }
> }
>
> catch let e as NSError
> {
> print("Error parsing model.json: \(e)")
> }
> ---
> JSON: ["images": (
>{
>thumb = url1;
>width = 10;
>},
>{
>thumb = url2;
>width = 20;
>}
> )]
> new: Optional(FOOBAR: url1)
> new: Optional(FOOBAR: url2)
> Optional({"images":[{"thumb":"url1","width":10},{"thumb":"url2","width":20}]})
> ---
>
> But it seems the way I drill down into the initial json dictionary gives me
> copies, or otherwise prevents me from modifying the dictionary like this.
>
> Any suggestions on what I can do? I really don't want to have to walk and
> rebuild the JSON myself.
>
> --
> Rick Mann
> rm...@latencyzero.com
>
>
>
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Re: Modify JSON in Swift
On Nov 6, 2015, at 22:54 , Rick Mann wrote: > > if var images = json["images"] as? [[String:AnyObject]] No, that won’t work because Swift dictionaries have *value* semantics, so you’re *asking* for a copy here. The same thing in Obj-C works because the variable ‘images’ would be a reference. One possible solution would be to change this: > if var json = try NSJSONSerialization.JSONObjectWithData(data, options: > .MutableContainers) as? [String:AnyObject] to this: > if var json = try NSJSONSerialization.JSONObjectWithData(data, options: > .MutableContainers) as? NSMutableDictionary and stick to the realm of NS collection classes, but it’s pretty ugly. The other issue you have to be careful of is that casting a NSDictionary to (say) ‘[String: AnyObject]’ is probably going to copy the dictionary (to a real Dictionary) anyway, because this is a conversion (i.e. copy) cast, not a pure bridging cast. The only cast (AFAIK) from an object that’s a NSDictionary to Dictionary *without* a conversion is ‘[NSObject: AnyObject]’. This particular case, of working with Obj-C-derived NSJSONSerialization JSON objects in Swift, is actually really really hard. If the structure of the JSON object is fixed, it’s probably easier to define a Swift struct for it (or rather, a hierarchy of nested structs, dictionaries and arrays), and populate it once at the start and reconstruct the serialization dictionary at the end. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
