I have the following Kotlin code:
fun getAdminUser(): User { return getAllUsers().first { it.userType == ADMIN } as User } If getAllUsers() doesn't have an element that matches the specified predicate, it throws a NoSuchElementException. I'm happy with this exception but would like to override the exception message to provide more context when it fails. Is it possible to do in Kotlin w/o try-catch?
You could use the firstOrNull function to achieve that.
fun getAdminUser(): User { return (getAllUsers().firstOrNull { it.userType == ADMIN } as? User) ?: throw NoSuchElementException("Element not found") } 
Use firstOrNull to get first element or have null and use the elvis operator to throw NoSuchElementException.
fun getAdminUser(): User { val user = getAllUsers().firstOrNull { it.userType == ADMIN } ?: throw NoSuchElementException("My custom exception message") return user as? User ?: IllegalStateException("The element was neither null nor an instance of User class") } Otherwise to do it in single line you can do something like this:
fun getAdminUser(): User { return getAllUsers().firstOrNull { it.userType == ADMIN }?.also { require(it is User) { "The element was neither null nor an instance of User class" } } ?: throw NoSuchElementException("My custom exception message") }
getAllUsers().firstOrNull { it.userType == ADMIN } ?: throw NoSuchElementException("my custom exception message")