Is it ok to use closures?

Development
1

I would like to learn how Java closures work, is it ok to use them in core? It requires Java8 that’s why I’m asking.

2

One of the reasons we upgraded to Java 8 (besides Java 6 being EOL) was to support new language features.

So yes, it is okay to use closures in openmrs-core (but not in any code that would have to be backported, e.g. bugfixes).

That said, don’t use them pointlessly in a way that impedes code readability. :slight_smile:

3

For instance, this fragment:

VisitService visitService = Context.getVisitService();
List<Visit> visits = Context.getVisitService().getVisitsByPatient(patient);
for (Visit visit : visits) {
    visitService.voidVisit(visit, "Patient deleted");
}

Can be rewritten as:

final VisitService visitService = Context.getVisitService();
List<Visit> visits = Context.getVisitService().getVisitsByPatient(patient);
visits.forEach(visit -> visitService.voidVisit(visit, "Patient deleted"));

Not much gain, and probably not more readable.

4

I think closures improve readability when you’re doing things like filtering collections.

E.g. the following, from Person.java, could be a one-liner using closures. (At least it could be a one-liner in Groovy. I don’t know if Java 8 is as expressive for functional idioms.)

public List<PersonAttribute> getActiveAttributes() {
	List<PersonAttribute> attrs = new Vector<PersonAttribute>();
	for (PersonAttribute attr : getAttributes()) {
		if (!attr.isVoided()) {
			attrs.add(attr);
		}
	}
	return attrs;
}
5

Here’s the one liner, a bit verbose though.

public List<PersonAttribute> getActiveAttributes() {
	return getAttributes().stream().filter(attr -> !attr.isVoided()).collect(Collectors.toList());
}

I wish it was possible to just do:

public List<PersonAttribute> getActiveAttributes() {
    return getAttributes().filter(attr -> !attr.isVoided());
}
6

I am looking forward to being able to use the new java 8 features (especially closures) but I’m curious if a decision has been made about which OpenMRS platform version will be the first to require java 8.

7

The decision was made for it to be the OpenMRS Platform 2.0!

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