I'm developing an Android application. I would like to use RxAndroid for form validation. I have done a lot of research on the internet but did not find a guide to take me through. Please help me out with how i can go about with the same, possibly with a small example. Thank you.
I found this tutorial, looks great: Reactive Forms with RxAndroid
First, add RxBinding to your project
RxBinding has a built in method for doing this,
RxTextView.textChanges(). It takes a EditText and returns an
Observable emmitting a CharSequence on each character change.
mInputLayout.setError("Invalid Credit Card Number")
Observable<Boolean> creditCardObservable = RxTextView.textChanges(mCreditCardInput)
.map(inputText -> (inputText.length() == 0) || inputText.toString().matches("credit card regex here"))
.distinctUntilChanged();
creditCardObservable.subscribe(isValid -> mInputLayout.setErrorEnabled(!isValid));
Repeat the process with more values, like:
mCreditCardInputLayout.setError("Invalid Email);
Observable<Boolean> emailObservable = RxTextView.textChanges(mEmailInput)
.map(inputText -> (inputText.length() == 0) || inputText.toString().matches("credit card regex here"))
.distinctUntilChanged();
emailObservable.subscribe(isValid -> mCreditCardInputLayout.setErrorEnabled(isValid))
And then we can enable the button when the values are valid:
Observable.combineLatest(
creditCardObservable,
emailObservable,
(creditValid, emailValid) -> creditValid && emailValid)
.distinctUntilChanged()
.subscribe(valid -> mSubmit.setEnabled(valid));
Optional retrolambda library
Related
I am trying to learn reactive programming, so forgive me if I ask a silly question. I'm also open to advice on changing my design.
I am working in scala-swing to display the results of a simulator. With one setting, a chart is displayed as a histogram; with the other setting the chart is displayed as the cumulative sum. (I'm probably using the wrong word; in the first setting you might have bin1=2, bin2=5, bin3=3; in the second setting the first height is 2, the second is 2 + 5, the third is 2 + 5 + 3, etc.). The simulator can be slow, so I originally used a Future to compute it, and the set the data into the chart. I decided to try a reactive approach, so my requirements are: 1. I don't want to recreate the data when I change the display mode, and 2. I want to set the Observable once for the chart and have the chart listen to the same Observable permanently.
I got this to work when I started the chain with a PublishSubject and the Future set the data into the start of the chain. When the display mode changed, I created a new PublishSubject().map(newRenderingLogic).subscribe(theChartsObservable). I am now trying to do what looks like the "right way," but it's not working correctly. I've tried to simplify what I have done:
val textObservable: Subject[String] = PublishSubject()
textObservable.subscribe(text => {
println(s"Text: ${text}")
})
var textSubscription: Option[Subscription] = None
val start = Observable.from(Future {
"Base text"
}).cache
var i = 0
val button = new Button() {
text = "Click"
reactions += {
case event => {
i += 1
if (textSubscription.isDefined) {
textSubscription.get.unsubscribe()
}
textSubscription = Some(start.map(((j: Int) => { (base: String) => s"${base} ${j}" })(i)).subscribe(textObservable))
}
}
}
On start, an Observable is created and logic to print some text is added to it. Then, an Observable with the generated data is created and a cache is added so that the result is replayed if the next subscription comes in after its results are generated. Then, a button is created. Then on button clicks a middle observable is chained with unique logic (it's a function that creates a function to append the value of i into the string, run with the current value of i; I tried to make something that couldn't just be reused) that is supposed to change with each click. Then the first Observable is subscribed to it so that the results of the whole chain end up being printed.
In theory, the cache operation takes care of not regenerating the data, and this works once, but onComplete is called on textObservable and then it can't be used again. It works if I subscribe it like this:
textSubscription = Some(start.map(((j: Int) => { (base: String) => s"${base} ${j}" })(i)).subscribe(text => textObservable.onNext(text)))
because the call to onComplete is intercepted, but this looks wrong and I wanted to know if there was a more typical way to do this, or architect it. It makes me think that I don't understand how this is supposed to be done if there isn't an out-of-the-box operation to do this.
Thank you.
I'm not 100% sure if I got the essence of your question right, but: if you have an Observable that may complete and you want to turn it into an Observable that never completes, you can just concatenate it with Observable.never.
For example:
// will complete after emitting those three elements:
val completes = Observable.from(List(1, 2, 3))
// will emit those three elements, but will never complete:
val wontComplete = completes ++ Observable.never
Good morning, everyone,
I am having a problem with the handling of two checkboxes which should be mutually exclusive, on the page we cannot put an id because multiselection is provided.
enter image description here
Here the zkoss code:
<cell colspan="2">
<checkbox
label="${labels.label.giaAddebitata}"
checked="#load(each.flagAddebitata eq '1')"
onCheck="#command('addebitata', fladd=event.checked,idPer=each.idPerizia )"
onFocus="#command('manageList', idPer=each.idPerizia)"
disabled="#load(each.statoContabile eq 4 ? true : false)"/>
</cell>
<cell colspan="2">
<checkbox
label="${labels.label.nonAddebitare}"
checked="#load(each.nonAddebitare eq '1')"
onCheck="#command('nonaddebitata',flnoadd=event.checked, idPer=each.idPerizia)"
onFocus="#command('manageList', idPer=each.idPerizia)"
disabled="#load(each.statoContabile eq 4 ? true : false)"/>
</cell>
and the java functions
#Command
#NotifyChange ({ "flagAddebitata","nonAddebitare", "selectedRic"})
public void addebitata(#BindingParam("fladd") boolean fladd,#BindingParam("idPer")int idPerizia ) {
boolean addebitata = fladd;
selectedRic = new HashSet<AddebitoClienteViewDTO>();
for(AddebitoClienteViewDTO add : carList) {
if(add.getIdPerizia() == idPerizia) {
add.setFlagAddebitata(booleanToString.apply(fladd));
selectedRic.add(add);
}
}
logger.debug("SELECTEDRIC non addebitare " + selectedRic);
logger.debug("addebitata funzione " +addebitata);
}
#Command
#NotifyChange ({ "nonAddebitare", "selectedRic"})
public void nonaddebitata(#BindingParam("flnoadd") boolean flnoadd,#BindingParam("idPer")int idPerizia ) {
boolean nonaddebitata = flnoadd;
selectedRic = new HashSet<AddebitoClienteViewDTO>();
for(AddebitoClienteViewDTO add : carList) {
if(add.getIdPerizia() == idPerizia) {
add.setNonAddebitare(booleanToString.apply(flnoadd));
selectedRic.add(add);
}
}
logger.debug("SELECTEDRIC non addebitare " + selectedRic);
logger.debug("nonaddebitata funzione " +nonaddebitata);
}
We tried using the && != " the != alone and adding another binding param to the java functions.
The result we want to achieve is that if one check is clicked the other if it is already selected loses the check.
Alternatively we tried the radiogroup but it does not allow the non-selection of radioboxes, one is always mandatory.
Is there a way to clear the radiobutton without a java clear function?
Thanks
That's a lot of code and hard to turn into a reproducing case due to all of the extra objects, so I'll focus more on the functional requirement.
From your description, I understand that what you want to create is a system in which you can either select "A", "B" or "none".
There is some unspecified behavior in there (like if "A" is selected, can I select "B" and automatically clear selection on "A"? Or does having "A" selected mean that "B" is non-selectable).
From your stated requirement, the component I would choose to express that structure is a dropdown menu with 3 choices ("not selected", "A", "B"), but that might not be what you are trying to achieve with the UI design here?
If you want to make something like that using checkboxes, you may want to keep a single state for the selection status, and a command to update the selection status.
See a simple code sample here: https://zkfiddle.org/sample/hb7f7k/1-Another-new-ZK-fiddle
The left 2 checkboxes work on a "unselect others if selected" workflow.
The right 2 checkboxes work on a "cannot select others while selected, but can unselect" workflow.
Note: that sample is a "bare minimum" implementation. In a real case, you'd improve it by factorizing the code, making it into a template, etc. rather than declaring these values inline.
In the non reactive world the following code snippet is nothing special:
interface Enhancer {
Result enhance(Result result);
}
Result result = Result.empty();
result = fooEnhancer.enhance(result);
result = barEnhancer.enhance(result);
result = bazEnhancer.enhance(result);
There are three different Enhancer implementations taking a Result instance, enhancing it and returning the enhanced result. Let's assume the order of the enhancer calls matters.
Now what if these methods are replaced by reactive variants returning a Flux<Result>? Because the methods depend on the result(s) of the preceding method, we cannot use combineLatest here.
A possible solution could be:
Flux.just(Result.empty())
.switchMap(result -> first(result)
.switchMap(result -> second(result)
.switchMap(result -> third(result))))
.subscribe(result -> doSomethingWith(result));
Note that the switchMap calls are nested. As we are only interested in the final result, we let switchMap switch to the next flux as soon as new events are emitted in preceding fluxes.
Now let's try to do it with a dynamic number of fluxes. Non reactive (without fluxes), this would again be nothing special:
List<Enhancer> enhancers = <ordered list of different Enhancer impls>;
Result result = Result.empty();
for (Enhancer enhancer : enhancers) {
result = enhancer.enhance(result);
}
But how can I generalize the above reactive example with three fluxes to deal with an arbitrary number of fluxes?
I found a solution using recursion:
#FunctionalInterface
interface FluxProvider {
Flux<Result> get(Result result);
}
// recursive method creating the final Flux
private Flux<Result> cascadingSwitchMap(Result input, List<FluxProvider> fluxProviders, int idx) {
if (idx < fluxProviders.size()) {
return fluxProviders.get(idx).get(input).switchMap(result -> cascadingSwitchMap(result, fluxProviders, idx + 1));
}
return Flux.just(input);
}
// code using the recursive method
List<FluxProvider> fluxProviders = new ArrayList<>();
fluxProviders.add(fooEnhancer::enhance);
fluxProviders.add(barEnhancer::enhance);
fluxProviders.add(bazEnhancer::enhance);
cascadingSwitchMap(Result.empty(), fluxProviders, 0)
.subscribe(result -> doSomethingWith(result));
But maybe there is a more elegant solution using an operator/feature of project-reactor. Does anybody know such a feature? In fact, the requirement doesn't seem to be such an unusual one, is it?
switchMap feels inappropriate here. If you have a List<Enhancer> by the time the Flux pipeline is declared, why not apply a logic close to what you had in imperative style:
List<Enhancer> enhancers = <ordered list of different Enhancer impls>;
Mono<Result> resultMono = Mono.just(Result.empty)
for (Enhancer enhancer : enhancers) {
resultMono = resultMono.map(enhancer::enhance); //previousValue -> enhancer.enhance(previousValue)
}
return resultMono;
That can even be performed later at subscription time for even more dynamic resolution of the enhancers by wrapping the whole code above in a Mono.defer(() -> {...}) block.
I wrote a function to update Validator rules on an input if a certain option was selected, using this method (the forms are built using FormGroup):
onValueChanged(data : any) {
let appVIP1 = this.vip1TabForm.get('option1');
let appVIP2 = this.vip2TabForm.get('option2');
let appVIP3 = this.vip3TabForm.get('option3');
//Set required validation if data is 'option3'
if(data != 'option3') {
//Due to initialization errors in UI, need to start with the case
//That there are validations, check to remove them
appVIP1.setValidators([]);
appVIP2.setValidators([]);
appVIP3.setValidators([]);
}
else {
appVIP1.setValidators([Validators.required]);
appVIP2.setValidators([Validators.required]);
appVIP3.setValidators([Validators.required]);
}
}
And I bind that function call to a click event on radio buttons (I initially used the guide from this answer, but the onChange function didn't bind correctly).
This works great, and if the user selects option 1 or 2, the validations are empty, and won't be triggered. If they select option 3, the validations are shown and submission is stopped. However, I run into the problem where the user submits, sees the error, and goes back to change to option 1 or 2. While the validator is cleared, my form still reads as invalid. I have multiple input fields I am validating, so I can't just set the form to valid if the validator is removed this way. How would I go about doing this? Can I remove the has-error for one particular field in the formgroup?
If the correct validators are in place, you can manually call AbstractControl#updateValueAndValidity after they select an option:
this.formBuilder.updateValueAndValidity();
(Where, of course, this.formBuilder is your FormBuilder instance.)
You can also call it on FormElements directly.
This is commonly used to trigger validation after a form element's value has been programmatically changed.
Instead of removing and adding validations. It is more simple to enable and disable fields. You need to add the Validators.required for all required fields. And disable the fields which are not required.
onValueChanged(data : any) {
let appVIP1 = this.vip1TabForm.get('option1');
let appVIP2 = this.vip2TabForm.get('option2');
let appVIP3 = this.vip3TabForm.get('option3');
if(data != 'option3') {
appVIP1.disable();
appVIP2.disable();
appVIP3.disable();
}
else {
appVIP1.enable();
appVIP2.enable();
appVIP3.enable();
}
}
I am trying to add some validation to our form for a field. It is the first .verifying below. At the moment even if it fails the new validation it then goes to check the rest of the .verifying and returns several error messages.
If the field fails my new validation I would like it to not do all the other verifying and just return. So basically if my field matches the regex for a temporary field, I want it to return an error message without continuing the rest of the validation.
val form = Form(
mapping(
"my_field" -> text
.verifying(Messages("error.field.temporary"), x => x.matches(TEMP_FIELD))
.verifying(Messages("error.mandatory", Messages("field")), _.length > 0)
.verifying(Messages("error.field.invalid"), x => x.length == 0 || MyField.isValid(x.toUpperCase()))
.verifying(Messages("error.field.invalid"), x => !MyField.isValid(x.toUpperCase()) || x.takeRight(1).toUpperCase().matches(FIELD_SUFFIX_REGEX))))
(MemberDetails.apply)(MemberDetails.unapply))
Any help appreciated.
I've solved this by using a constraint. Good information is available here: https://www.playframework.com/documentation/2.4.x/ScalaCustomValidations