An example of creating a Swift like guard let extension function in Kotlin with rule validation

GuardLetKotlinExtension.kt

inline infix fun EditText.guard(rule:Boolean,call: () -> Unit): String? {
    if (this.text.isNotEmpty() && rule) return text
    else {
        call()
        return null
    }
}

fun String.isEmail(): Boolean {
    val p = "^(\\w)+(\\.\\w+)*@(\\w)+((\\.\\w+)+)\$".toRegex()
    return matches(p)
}

//example of usage

val phone = field.guard(field.isEmail()){
  println("Your phone is incorrect!")
  return null
}
println($phone)