How to get prefixes from synchronous parser.parse?

[JaLe29]

I want to use synch version of parse.

Like this:

const N3 = require('n3');
const parser = N3.Parser();
let data = parser.parse(content);

Now, in var data are triples.

In async version:

parser.parse(content, (error, triple, prefixes) => {
			if (triple) {
					//subject: triple.subject,
					//predicate: triple.predicate,
					//object: triple.object
			} else {
				Object.keys(prefixes).forEach((key, index) => {
						//index: index,
						//prefix: prefixes[key]
				});

			}
		})

Is possible to get prefixes, how can I get prefixes using sync version?

[RubenVerborgh]

This is currently not supported, and I unfortunately do not see an easy way to add this without changing the interface. Is async an option for you?

[JaLe29]

So, sync version is better for me.

Now I must use ugly active waiting over async version.

Like this:

                  let ret 
                  parser.parse(content, (error, triple, prefixes) => {
			if (triple) {
					//subject: triple.subject,
					//predicate: triple.predicate,
					//object: triple.object
			} else {
				Object.keys(prefixes).forEach((key, index) => {
						//index: index,
						//prefix: prefixes[key]
				});
                                ret = true
			}
                })

		while (ret === undefined) {
			require('deasync').runLoopOnce();
		}

So, I know, its not best way, but I must use sync.

[RubenVerborgh]

Now I must use ugly active waiting

Well, not really a “must” 😉 You can just call whatever code comes next as a function when you're done. There's no inherent need to be sync in JavaScript.

But I agree it would be nice if the prefixes were returned in sync mode. Given that we have a breaking interface change pending anyway (#118), we might also do this.

[JaLe29]

You can just call whatever code comes next as a function when you're done

I know... :-)

Ok, thank you

[artonio]

So I essentially ended up doing something like this (sorry for TypeScript).

`getQuadsAndPrefixes(ttlData: string, parser: any) {

    return new Promise((resolve, reject) => {

        const quads = [];
        const prefixes = [];
        parser.parse(ttlData, (e, q, p) => {
            if (e) {
                reject(e);
            }
            if (q) {
                quads.push(q);
            }
            if (p) {
                prefixes.push(p);
            }
            resolve({quads: quads, prefixes: prefixes});
        });
    });
}`

This returns a Promise, while this is great on server side (e.g Node), it's not ideal on the client if you don't want to use promises.

Hope this helps someone.

[RubenVerborgh]

Note that your wrapper function isn't yet correct: it should only resolve if there is no triple (named q in your code).

While I don't see why there should be a difference between server and client (it's just JavaScript), note that consuming code isn't obliged to use promises: you can just use async/await.

[artonio]

Do you mean something like this:

if (q) {
        quads.push(q);
} else {
       resolve({quads: quads, prefixes: prefixes});
}

And yes I am using async/await, but that means that I have to make all my functions async in order to do await, which is not the biggest deal i suppose.