var myEmailStr = "[email protected]"
var isValid = myEmailStr.validEmail<Int>()  // isValid will be true or false

// Or you can also validate with an error callback method
myEmailStr.validEmail<String>() {
    // This method will be called when myEmailStr is not a valid email.
    Toast.makeText(contex, it, Toast.LENGTH_SHORT).show()
}

var myEditText = findViewById<EditText>(R.id.myEditText)
var isValid = myEditText.nonEmpty<String>()        // Checks if edit text is empty or not

// Or with error callback method like this
myEditText.nonEmpty<String>() {
    // This method will be called when myEditText is empty.
    myEditText.error = it
}

var txtPassword = findViewById<EditText>(R.id.txtPassword)
txtPassword.validator<String>()
           .nonEmpty()
           .atleastOneNumber()
           .atleastOneSpecialCharacters()
           .atleastOneUpperCase()
           .addErrorCallback { 
                txtPassword.error = it
                // it will contain the right message. 
                // For example, if edit text is empty, 
                // then 'it' will show "Can't be Empty" message
           }
           .check()

class EmailRule<ErrorMessage>(
    var errorMsg: ErrorMessage? = null,
    clazz: Class<ErrorMessage>
) : BaseRule<ErrorMessage>(clazz) {
    // add your validation logic in this method
    override fun validate(text: String) : Boolean {
        // Apply your validation rule logic here
        return text.matches(Regex("^([a-zA-Z0-9_.-])+@([a-zA-Z0-9_.-])+\\.([a-zA-Z])+([a-zA-Z])+"))
    }
    
    // Add your invalid check message here
    override fun getErrorMessage(): ErrorMessage? {
        return when {
            errorMsg != null -> errorMsg
            typed(kotlin.String::class.java, java.lang.String::class.java) -> "Invalid Email Address!" as? ErrorMessage
            typed(kotlin.Int::class.java, java.lang.Integer::class.java) -> R.string.vald_invalid_email_address as? ErrorMessage
            else -> throw MismatchErrorTypeException()
        }
    }

    override fun setError(msg: ErrorMessage?) {
        errorMsg = msg
    }
}

var myEditText = findViewById<EditText>(R.id.myEditText)
var myEditText.validator<String>()
    .addRule(EmailRule())
    .addErrorCallback { 
        // In case of invalid, this method will be called.
        // The 'it' will be "Please enter valid email address" message.
        myEditText.error = it
    }
    .check()

var edtFirstName = findViewById<EditText>(R.id.edtFirstName)
var edtLastName = findViewById<EditText>(R.id.edtLastName)
var edtEmail = findViewById<EditText>(R.id.edtEmail)
var edtPassword = findViewById<EditText>(R.id.edtPassword)

if (edtFirstName.nonEmpty<String>() && edtLastName.nonEmpty<String>() 
    && edtEmail.nonEmpty<String>()&& edtPassword.nonEmpty<String>()) {
    // All views are non-empty. You are safe to submit the data to server.
}
else {
    // Any one or more fields are empty. Show the error to the user
    // to fill the whole form.
    // You don't know which field is empty. So you might need to find it.
}

var edtFirstName = findViewById<EditText>(R.id.edtFirstName)
var edtLastName = findViewById<EditText>(R.id.edtLastName)
var edtEmail = findViewById<EditText>(R.id.edtEmail)
var edtPassword = findViewById<EditText>(R.id.edtPassword)

// Empty check
nonEmptyList<String>(edtFirstName, edtLastName, edtEmail, edtPassword) { view, msg ->
    view.error = msg
    // The view will contain the exact view which is empty
    // The msg will contain the error message 
}

// Min-length Check - all views should have atleast 5 characters
minLengthList<String>(5, edtFirstName, edtLastName, edtEmail, edtPassword) { view, msg ->
    view.error = msg
    // The view will contain the exact view which is less than 5 characters
    // The msg will contain the error message 
}

var myNumber = "1234567"
var validator = Validator<String>(myNumber)

validator.startWithNumber()
    .addErrorCallback { msg ->
        // Do something here with the error.
        // The msg variable contains the error message
    }
    .addSuccessCallback {
        // Validation checks are passed. The text is valid.
        // Do anything with success case here.
    }
    .check()

    val editTextPassword = bindValidator<String>("", true)
        .nonEmpty("Please enter your password.")
        .regex(".*[A-Z]+.*", "Must contain capital letters.")
        .regex(".*[0-9]+.*", "Must contain digits.")
        .regex(".*[a-z]+.*", "Must contain small letters.")
        .minLength(8, "Eight or more characters.")
        .maxLength(16, "No more then sixteen characters.")

<com.google.android.material.textfield.TextInputLayout
    android:id="@+id/edt_lay_password"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="@dimen/_10sdp"
    app:errorEnabled="true"
    app:error="@{viewModel.editTextPassword.error ?? ``}"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/btnValidation">

    <com.google.android.material.textfield.TextInputEditText
        android:id="@+id/edt_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="textPassword"
        android:text="@={viewModel.editTextPassword.value}"
        android:hint="Password"/>

</com.google.android.material.textfield.TextInputLayout>

    if(editTextPassword.check()) {
        Log.e(TAG, "True ${editTextEmail.getError()}")
    } else {
        Log.e(TAG, "False ${editTextEmail.getError()}")
    }