bugsbunnybr / form

Repository for kotlin form validation

FORM

Form makes it easy to format and validate form fields and submit the form when every thing is ready.

And it come in many flavors:

• Form for the 100% pure Kotlin library;
• RxForm for RxJava lovers;
• LiveDataForm for DataBinding/LiveData addicts;

How to Form

1. Create a Form.Builder<T>() where T is the type of each field key;
2. Set the callbacks for the validation events, like builder.setFieldValidationListener() or builder.setValidSubmitListener();
3. Call builder.addField() as many fields you would like to have in form;
4. Execute the builder.build() method to get a hold of a Form instance;
5. Every time the user requests to submit the form, call the method form.doSubmit();

In the sample below we use Int as T because we are using the Android R.id.$viewId Int as keys and String as R since email and password are EditTexts.

val emailChanges = ObservableValue(email.text.toString())
val passwordChanges = ObservableValue(password.text.toString())

email.addTextChangedListener(getTextWatcher(emailChanges))
password.addTextChangedListener(getTextWatcher(passwordChanges))

val emailField = FormField(
        emailContainer.id,
        emailChanges,
        emailValidations
)

val passwordField = FormField(
        passwordContainer.id,
        passwordChanges,
        passwordValidations
)

val form = Form.Builder<Int>()

        .setFieldValidationListener(this)
        .setFormValidationListener(this)
        .setValidSubmitListener(this)
        .setSubmitFailedListener(this)

        .addField(emailField)
        .addField(passwordField)

        .build()

submit.setOnClickListener {
    form.doSubmit()
}

Full sample here

How to RxForm

RxForm README

How to LiveDataForm

LiveDataForm README

FormField<T,R> properties

FormField.key<T>

• It's an ID to identify uniquely the field in a form. Of type T.

FormField.input<R>

• It's an IObservableValue<R> used to feed the field value change events to the form.

FormField.errors<List<ValidationMessage>>

• It's an IObservableValue<List<ValidationMessage>>, call IObservableValue.addChangeListener() to add a ChangeObserver. This is where the form will deliver the validation changes events for this field.

FormField.enabled<Boolean>

• It's an IObservableValue<Boolean>, use this to enable or disable the form validation and submission for this field.
• Setting it with True will cause a field validation if the form strategy allows.
• Setting it with False will cause the FormField.errors to be called with an emptyList if the form strategy validation allows.
• Setting it with False or null will stop calling its validators and remove this field from the form submission data.

FormField.validators<R>

• It's a list of Validator<R>. Each validator will be called in order to process a round of validation for this field.

FormField.validationTriggers<Unit>

• It's a list of IObservableChange<Unit> used to force a round of validation to happen to this field if the form strategy allows.

Form events

There are four standard callbacks in every flavor of Form, depending on the form flavor you choose to use the events are delivered as a pure Kotlin callbacks, an Observable emissions or LiveData events. Does not matter the flavor, the behavior and naming should be consistent enough to understand what is happening.

FieldValidationChange

• It's triggered when a given field validation state change. This callback gives access to a Pair<T,List<ValidationMessage>> if the list is empty, the field identified by the key T is valid.
• This callback allows you to set/unset a error message for each screen field of a form.
• It has the same behavior of FormField.errors.

FormValidationChange

• It's triggered when the form validation state change. A boolean is used to indicate if the form is valid as a whole or not.
• This callback allows you to enable or disable a submit button or hint the user about the form state.

ValidSubmit

• It's triggered when a valid submit happens. This callback gives access to a List<Pair<T, Any?>> where T is a field key, and the Any? is that field current value.
• This callback is called to allow you to send the form data to your server.
• You also can use FormField.input.value to read the current value of a field when submitting.

SubmitFailed

• It's triggered when a submit happens, but the form is not valid. This callback gives access to a List<Pair<T, List<ValidationMesage>>> where T is a field key and List<ValidationMessage> indicates how many validations failed for that given field.
• This callback can be used to scroll to a invalid field after a submit.

VALIDATION

As an optional dependency we offer the possibility to use our validators module.

A form validation is related to each field validation, so we need to define a list of validators for each field in the form. You can define your own validators by implementing the Validator<T> interface, in the sample below we define an HoursValidator and a ValidationMessage. A ValidationMessagetakes amessageto be shown to the user when the validation fails and aValidationTypethat was created to specify which type of validation failed (you can have multiple validators with the sameValidationType`).

Note that your form can validate any type of input, here we used String, but your implementation can be of any class that you define and implements the isValid method.

class HoursValidator(val message: String, val divider: String) : Validator<String> {
    override fun validationMessage(): ValidationMessage {
        return ValidationMessage(message = message, validationType = HOUR_FORMAT)
    }

    override fun isValid(input: String?): Boolean {

        input ?: return false

        return try {
            val parts = input.split(divider)
            val hours = parts.firstOrNull()?.toInt() ?: -1
            val minutes = parts.lastOrNull()?.toInt() ?: -1
            (parts.size == 2
                    && hours >= 0
                    && hours <= 23
                    && minutes >= 0
                    && minutes <= 59)
        } catch (e: Throwable) {
            false
        }
    }
}

FORMATTERS

As an optional dependency we offer the possibility to use our formatters module. Usually a formatter is coupled with the field validation. A field that displays hour and minutes (HH:MM) could be valid if the the hours and minutes are valid only if in a given format. So a given formatter is used together with a given validator.

// 00:00
class HoursFormatter(val divider: String) : TextFormatter {
    private val digitsOnlyRegex = "[^0-9]".toRegex()

    override fun getCursorPosition(previous: String, input: String, output: String) = output.length

    override fun format(input: String): String {
        val clearText = input.toDigitsOnly()

        return when (clearText.length) {
            0, 1 -> clearText
            2, 3, 4 -> clearText.substring(0, 2) + divider + clearText.substring(2)
            else -> clearText.substring(0, 2) + divider + clearText.substring(2, 4)
        }
    }

    private fun String.toDigitsOnly(): String {
        return replace(digitsOnlyRegex, "")
    }
}

Note that each implementation of TextFormatter has a getCursorPosition() method that should return where the field cursor should be positioned after each change in the input field. A more general interface Formatter<T> can be used when the cursor position is not important or possible to be implemented.

Download

Download or grab via Maven:

<dependency>
  <groupId>br.com.youse.forms</groupId>
  <artifactId>form-jdk</artifactId>
  <version>0.7.0</version>
</dependency>

or Gradle:

add

        maven { url 'https://oss.sonatype.org/content/groups/public' }

and

implementation 'br.com.youse.forms:form-jdk:0.7.0'
implementation 'br.com.youse.forms:rx-form-jdk:0.7.0'
implementation 'br.com.youse.forms:validators-jdk:0.7.0' // optional
implementation 'br.com.youse.forms:formatters-jdk:0.7.0' // optional