Different Problem: Attempting to add static function to Json.hx for explicit type return

Haxe
#1

I am looking for the Json class in the haxe package on Github, but for some reason I cannot seem to find it! I was thinking of implementing a Generic type into the encode function as a “helper” function if you want to explicitly provide a Class for the given JSON to cast on before it’s returned. This would be very helpful but I can’t find the source code anywhere…

I was thinking something along the lines of this:

public static function encode<T>(data:String):T
{
    var instance = Type.createInstance(T);
    var fields:Array<String> = Type.getClassFields(instance);
    for (field in fields)
    {
        Reflect.setField(instance, field, getValueOfFieldInData(data));
    }
    return cast(instance, T);
}

And just wrap that around the existing code… wherever it is… obviously I would need to test it because I don’t even know if that will work, but it would save a hell of a lot of time.

Nevermind, found it: https://github.com/HaxeFoundation/haxe/blob/development/std/haxe/Json.hx Posted the topic before searching…

EDIT: Now I am having a difficult time:

/**
        Parses the given JSON-encoded `text` and returns the given Class type
        with the information found in the text.
        
        If given `text` is not valid JSON, an exception will be thrown.
    **/
        public static function decode<T>(cls:Class<T>, text:String):T
        {
            var casted = Type.createEmptyInstance(cls);
            var obj = Json.parse(text);
            var fields = Reflect.fields(obj);
            for (item in fields)
            {
                trySetField(casted, item, Reflect.field(obj, item));
            }
            return casted;
        }
    
        private static function trySetField<T>(obj:Class<T>, field:String, value:Dynamic):Void
         {
            try
            {
                Reflect.setField(obj, field, value);
            }
            catch (msg:String)
            {
            
            }
        }

The following code results in the following error:

encode.T should be Class<Unknown<0>>
for function argument 'obj'

I am really not sure how to solve this…

THE ULTIMATE EDIT OF ALL ULTIMATES: I am just going to create a new bloody class and copy the WORKING code…

Okay, now I truly do have a problem which I would like to dicuss because this is rather amusing:

http://try.haxe.org/#f42f6 This is some test code, and you can build and it works. It parses everything correctly as you would expect.

Now look at this:

nOsyaWs.png1209×527 78.9 KB

The exact same code (just with traces) purely to try and resolve this problem, but I don’t understand why it works on the try.haxe.org website, and not in a standalone Flash Player… So confusing…

Tested in Neko, and prints out correctly … Obviously just a problem with Flash Player

#2

Flash Player is very particular about object casting, you will need to copy the properties over from the original JSON to a new instance that matches the same signature (C++ would also have runtime problems with casting)

#3

You means fields, right? Fields and properties are technically different things in this case :wink:

That’s in theory what the code is already doing, though. I think…

var casted = Type.createEmptyInstance(_cls);

This line creates the “signature” of the class to return.

var obj = Json.parse(_data); 
var fields = Reflect.fields(obj);

These two lines get the fields of the Json object, essentially the signature of the JSON.

for (item in fields)
{
    trySetField(casted, item, Reflect.field(obj, item));
}

And then those lines attempt to set the field value in the casted object with the given name and field within the JSON.

Sorry, I suppose the variable casted doesn’t really make sense since it’s a new instance of something, so maybe I should call it instance instead.

I just realised the target I was working in on the haxe website was JavaScript, so that works fine but all other targets don’t… I wonder why… oh, yeah. JSON!