Nice.
Sounds like everyone is leaning towards "no". Would it be worth submitting
a PR to include more usage examples - which I assume could also serve as a
place to collect more feedback? Or just keep it within this thread given
the way it's leaning? (or unless that consensus changes)
Ultimately in my web/UI project the reduction (after using function(...))
is something like...
Failable.asFunction(Parent::getChild)
.andThen(Optional::ofNullable)
.andThen(o -> o.map(Child::getGrandChild))
.andThen(o-> o.map(GrandChild::getName).orElse(defaultValue));
vs my util method
FunctionUtils.nested(Parent::getChild, Child::getGrandChild,
GrandChild::getName, defaultValue);
So it's still a big difference in clarity for me, given how often its used.
FWIW - My project is using Vaadin, and this util function is used to bind
nested bean properties to Vaadin input fields. On that note - In addition
to the bean "getter" binding, it also uses a similar util method to bind
bean "setter" methods - because input fields obviously need access to both.
The setter util call looks similar, with the last argument being
a BiConsumer...
FunctionUtils.nested(Parent::getChild, Child::getGrandChild,
GrandChild::setName);
Although in general this code does not reference any Vaadin specific
functionality, the overall use case may be quite specific to those needs,
so all of these utilities may be better suited to a utils class within a
vaadin specific library.
Dan
On Fri, Aug 4, 2023 at 9:11 PM Gary Gregory <garydgreg...@gmail.com> wrote:
> The function() method is a great technique, it's now in Functions and
> FailableFunction (git master).
>
> I'll see later if it can be used within Lang. I know I can use it in other
> projects.
>
> Wrt an API for a vararg of functions that implements chaining internally,
> I'm not so sure. I've though I needed something like that in past, but I've
> always ended up with other coding patterns I found better at the time for
> whatever reason..
>
> Gary
>
> Gary
>
> On Fri, Aug 4, 2023, 3:24 PM Gary Gregory <garydgreg...@gmail.com> wrote:
>
> > Worth adding adding function(Function)? Seems low cost to add it
> > FailableFunction.
> >
> > Gary
> >
> > On Fri, Aug 4, 2023, 2:04 PM Rob Spoor <apa...@icemanx.nl> wrote:
> >
> >> With just one simple utility method you can get all the chaining you
> want:
> >>
> >> public static <T, R> Function<T, R> function(Function<T, R> func) {
> >> return func;
> >> }
> >>
> >> This doesn't look very useful, but it allows you to turn a method
> >> reference or lambda into a typed Function without needing a cast. After
> >> that it's really simple using what's provided in the Java API:
> >>
> >> Function<MyBean, String> func = function(MyBean::getChild)
> >> .andThen(Child::getName);
> >>
> >> You want a default value? Almost just as easy:
> >>
> >> someFrameworkThing.setProperty(function(ParentBean::getChild)
> >> .andThen(ChildBean::getName)
> >> .andThen(Optional::ofNullable)
> >> .andThen(o -> o.orElse("defaultName"));
> >>
> >>
> >> On 04/08/2023 16:04, Daniel Watson wrote:
> >> > Asking for comments and thoughts on a potential new feature. Already
> >> > developed in a commons-like style, but dont want to submit PR without
> >> > discussion as it may be considered out of scope or too use case
> >> specific.
> >> >
> >> > Justification and details...
> >> >
> >> > I've run into a scenario a few times where nested lamba functions
> would
> >> be
> >> > incredibly useful. e.g.
> >> >
> >> > MyBean::getChild::getName
> >> >
> >> > Obviously this is not a language feature, but can be simulated in a
> >> useful
> >> > way. So far my use has mostly been related to code that works with
> POJO
> >> > beans, and frameworks that use function references to understand those
> >> > beans and properties. Specifically useful where the context of the
> code
> >> > block is the parent entity, but you need to reference a child, and
> >> without
> >> > nested lambdas you end up with things like the below...
> >> >
> >> > ParentBean parentBean = new ParentBean();
> >> > parentBean.setChild(new ChildBean("name"));
> >> > //imagine that FrameworkThing is a generic class, and thus the generic
> >> type
> >> > is ParentBean
> >> > FrameworkThing someFrameworkThing = new FrameworkThing
> >> (ParentBean.class)
> >> > //but we need to get to a property of a child bean
> >> > someFrameworkThing.setProperty((parentBean) -> {
> >> >
> >> > return parentBean.getChild().getName();
> >> >
> >> > });
> >> >
> >> > Obviously this could be handled with a getChildName() method on the
> >> parent
> >> > bean, but that has pitfalls as well (e.g. bean class cannot be
> changed,
> >> or
> >> > adding of properties interferes with other usage of the class e.g.
> JPA,
> >> > JAX). However with a util class the second call can be reduced to
> >> > something like below, leaving the bean API untouched.
> >> >
> >> >
> >>
> someFrameworkThing.setProperty(FunctionUtils.nested(ParentBean::getChild,ChildBean::getName));
> >> >
> >> > Taken alone, that single reduction may seem trivial, but in a scenario
> >> > where these nested references are commonly needed, the reduction makes
> >> the
> >> > code clearer (In my opinion), as it is immediately apparent on a
> single
> >> > line of code that the reference is a simple nested property, rather
> than
> >> > having to interpret an inline lambda function. It also discourages
> >> errant
> >> > placement of code by avoiding the inline function (since the only
> >> purpose
> >> > of the lambda was to retrieve a single nested value). In addition, If
> >> > intermediate nulls need to be handled then the reduction becomes more
> >> > apparent, as the null checks can be handled in the util class rather
> >> than
> >> > cluttering the app code. e.g.
> >> >
> >> >
> >>
> someFrameworkThing.setProperty(FunctionUtils.nested(ParentBean::getChild,ChildBean::getName,"defaultName"));
> >> > //or...
> >> >
> >>
> someFrameworkThing.setProperty(FunctionUtils.nested(ParentBean::getChild,ChildBean::getName,null));
> >> >
> >> > The third parameter here is a String (typed genetically based on the
> >> return
> >> > type of getName) and indicates the default value to be returned if the
> >> > first call to getChild() returns null. e.g. it replaces something
> >> like...
> >> >
> >> > someFrameworkThing.setProperty((parentBean) -> {
> >> >
> >> > ChildBean cb = parentBean.getChild();
> >> > if(cb == null) return null; //or other default value
> >> > else return cb.getName();
> >> >
> >> > });
> >> >
> >> > Given that commons-lang aims to extend existing language features,
> this
> >> > seemed like a reasonable place for a nested lambda util class. So far
> my
> >> > concerns are...
> >> >
> >> > 1. Does this feel too specific to an application to warrant
> >> inclusion in
> >> > commons? (For me it has been useful enough to place into a common
> >> library,
> >> > but commons-lang has a broader scope)
> >> > 2. If not commons-lang, is there some other commons library that
> >> this is
> >> > more suited to?
> >> > 3. There are still wrinkles that may prove complex and potentially
> >> > overly specific e.g. exception handling. Does that potential
> >> complexity
> >> > make it not worth adding?
> >> > 4. Assuming the features discussed here *are* valuable, Is
> handling
> >> only
> >> > java.util.Function a complete-enough feature? Or is it useless
> >> unless it
> >> > also attempts to handle BiFunctions - which become increasingly
> >> complex
> >> > (potentially unfeasible) to implement - i.e. is it too big a
> >> feature to
> >> > consider including?
> >> >
> >> > If folks feel like this is a solid "no" let me know. If the devil is
> in
> >> the
> >> > details and we need to see the PR first I can do that as well.
> >> >
> >> > Dan
> >> >
> >>
> >>
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> >>
> >>
>
