I am trying to take an array of structs with various keys and be able to filter each struct to only return a subset of the data. For example:

aPartners = [
  {
   "partnerid":1,
   "partnername": "Partner 1",
   "partnercode": "pt1",
   ...
   "configsettings: {
     ...
   } 
  },
  {
   "partnerid":2,
   "partnername": "Partner 2",
   "partnercode": "pt2",
   ...
   "configsettings: {
     ...
   } 
  }
];
allowedKeys = ["partnername","partnercode"];

How to process the above (arrayReduce/Map etc) to produce an array of structs with just partnername and partnercode in each struct. I tried this but it doesn’t work as needed:

allowedKeys = ["partnername","partnercode"];
for(partner IN aPartners) {
    objKeys = structKeyArray(partner);
	result = objKeys.reduce(function(accumulator, ele)  {
        if( allowedKeys.findNoCase(ele) ) {
			obj = {
				"#ele#": partner[ele]
			};
			return accumulator.append(obj);
		} else {
		    return accumulator;
		}
	}, []); 
};

What should I be using?

If you're starting with an array, and aiming to get out an array of the same size, then you should be using arraymap.

Ok, will give thqt a go. I always seem to start trying to use reduce when I need to use map.

Inside the map closure, you probably use structfilter to get a smaller struct.

Do the structs always have the keys that you want to map across? If so... no need to filter, just return the specific struct, eg: https://trycf.com/gist/4125fd967a56e8f71f0dadb2afd69452/acf2021?theme=monokai NB: it always helps ppl help you if your sample data is syntactically correct / complete.

Yeah, sorry, added the ellipsis to indicate presence of other keys.I am exploring an idea for our API to allow a client to request a subset of fields that would normally be returned by the endpoint. So an organisations endpoint that defaults to return an array of organisations could be asked to just return the organisation name and postcode for example.

what did you come up with? I got this: https://trycf.com/gist/32055f68b067ae3dae95881b3f956c51/lucee5?theme=monokai The key bit is this:

justTheImportantStuff = aPartners.map(
    (partner) => allowedKeys.reduce(
        (subStruct, key) => substruct.insert(key, partner[key]),
        {}
    )
)

So far, just tweaked my original: https://trycf.com/gist/d42c6d88d5b4441b2f7e2b4b87923896/lucee5?theme=monokai Yours looks a lot more straightforward.

The whole

var loc

thing is a bit "CF9". You know there's a

local

scope now, yeah?

Old habits!

and actually... if I may... you don't need any of your intermediary variables in there anyhow!

public array function filterAllowedObjectProperties(
	required array objArray,
	array allowedProperties=[]
) {
	if(!arguments.allowedProperties.len()) {
		return arguments.objArray;
	}
	return arguments.objArray.map(
	    (obj) => allowedProperties.reduce(
			(subStruct, key) => subStruct.insert(key, obj[key]),
			{}
		)
	)
}

(I've also switched from

arrayLen

to just

len

as the rest of the code is using obj.method not function(obj), so keeping it uniform; but that's a small thing)

Perfect! Many thanks for the updated example - implemented. Just tried the concept on one of our public endpoints that returns a bunch of news stories with a lot of data. 10 stories returns approx 55k of data. Add the fields filter is able to reduce it down depending on the data that is actually required. If I just need the news headline and associated organisation I can reduce the request size down to 2.3k of data.