https://issues.apache.org/jira/browse/WICKET-6379
Martin Grigorov Wicket Training and Consulting https://twitter.com/mtgrigorov On Wed, May 24, 2017 at 10:45 PM, Sven Meier <s...@meiers.net> wrote: > Hi, > > WDYT ? Do we need to implement #detach() in #map(), #filter(), etc ? >> > > yes, I think this is a good idea: the returned model holds a reference to > the given model, so it should detach it. > > Regards > Sven > > On 24.05.2017 21:36, Martin Grigorov wrote: > >> On Tue, May 23, 2017 at 11:17 PM, Martin Grigorov <mgrigo...@apache.org> >> wrote: >> >> Hi, >>> >>> On Tue, May 23, 2017 at 5:40 PM, Ihmehlmenn <ihmehlm...@gmx.de> wrote: >>> >>> Hello everyone, >>>> >>>> while trying out some of the very cool new features in Wicket 8, >>>> specifically replacing PropertyModels with lambda expressions, I had a >>>> few >>>> questions coming up. Most of them have been answered by the great guide >>>> provided, but following things are still a bit unclear to me: >>>> >>>> Thank you for testing the milestone release and for the feedback! >>> >>> >>> 1) Read-Only Models >>>> Let's say I want to replace the following PropertyModel for showing the >>>> "name" property of a Person obejct in a Label >>>> >>>> new PropertyModel<String>(personModel, "name"); >>>> >>>> with a lambda expression. Which of the following would be the best >>>> approach >>>> and why? >>>> >>>> LambdaModel.of(personModel, Person::getName); >>>> >>>> This way of using LambdaModel is indeed the same as the second way. The >>> advantage LambdaModel has is that you can also set a value when you use >>> the >>> method with the Supplier. >>> >>> >>> personModel.map(Person::getName); >>>> personModel.flatMap(...); // not quite sure yet when to use this one. >>>> See >>>> next question as well >>>> >>> >>> The first two options seem to be identical at the first glance but I >>>> noticed >>>> that the LambdaModel does call detach() on the underlying base model >>>> (just >>>> like the PropertyModel does), whereas the model created by the map() >>>> method >>>> doesn't seem to do that. >>>> >>>> This is a good point! >>> I think it is a bug that should be fixed! >>> >>> Actually here we use closure so adding #detach() is not possible unless >> the >> body is rewritten to instantiate an IModel with #getObject() and #detach() >> impls. >> I am not sure it is worth it. >> @Devs WDYT ? Do we need to implement #detach() in #map(), #filter(), etc ? >> >> >> >>> >>>> 2) Readable/Writeable Models >>>> The documentation has the following example for mapping a model to a >>>> readable/writeable model of a property >>>> >>>> IModel<String> personNameModel = personModel.flatMap(targetPerson -> >>>> LambdaModel.of( >>>> () -> targetPerson::getName, targetPerson::setName >>>> )); >>>> >>>> Why is the call to flatMap() needed? Isn't just using the LambdaModel >>>> the >>>> same but shorter? >>>> >>>> IModel<String> personNameModel = LambdaModel.of(personModel, >>>> Person::getName, Person::setName); >>>> >>>> IModel#flatMap() is like java.util.Optional#flatMap(). >>> It is useful when you already have another IModel impl that knows how to >>> set/get the name of a person. >>> LambdaModel#of(IModel<X>, SerializableFunction<X,R>, >>> SerializableBiConsumer<X,R>) is an easy way to create such IModel impl by >>> using Java 8 lambdas. >>> We should cross-reference them in the javadoc! >>> >>> Another discussion on this topic: http://markmail.org/ >>> message/m6l2w3ryqbdew2co >>> >>> >>> >>>> 3) Constants in Models >>>> In some cases I need to set a static constant value as read only model >>>> in >>>> a >>>> component. Up until now I simply used >>>> Model.of(Constants.MY_STATIC_VALUE); >>>> which probably results in the value being serialised into the session of >>>> the >>>> user. >>>> >>>> The model and its content are serialized with the page. >>> The page is stored in the http session only after being rendered. Once >>> you >>> move to another stateful page it is replaced by it and from there on it >>> is >>> stored only on the disk. >>> >>> >>> Am I assuming correctly, that using following lambda expression as model >>>> is >>>> more "efficient", since the static constant isn't serialised anymore >>>> this >>>> way? >>>> () -> Constants.MY_STATIC_VALUE; >>>> >>>> Correct! >>> The static constant won't be serialized but the closure will be. >>> So this version should be close memory-wise to using >>> AbstractReadOnlyModel >>> for this use case but anonymous inner classes have a reference to the >>> outer >>> instance and afaik lambdas don't have it. >>> >>> >>> >>>> Thanks to everybody pouring so much time into developing Wicket! >>>> >>>> Daniel Radünz >>>> >>>> -- >>>> View this message in context: http://apache-wicket.1842946.n >>>> 4.nabble.com/Questions-regarding-Wicket-8-and-lambda-express >>>> ions-for-models-tp4677918.html >>>> Sent from the Users forum mailing list archive at Nabble.com. >>>> >>>> --------------------------------------------------------------------- >>>> To unsubscribe, e-mail: users-unsubscr...@wicket.apache.org >>>> For additional commands, e-mail: users-h...@wicket.apache.org >>>> >>>> >>>> >
