Creating encrypted Realm and attempting to catch any exception thrown.

gistfile1.txt

var configuration = Realm.Configuration.defaultConfiguration

let encryptionKey = NSMutableData(length: 64)!
SecRandomCopyBytes(kSecRandomDefault, encryptionKey.length, UnsafeMutablePointer<UInt8>(encryptionKey.mutableBytes))
configuration.encryptionKey = encryptionKey
        
let filename = "private.realm"
let fileURL = configuration.fileURL?.URLByAppendingPathComponent(filename)
configuration.fileURL = fileURL

var realm: Realm!
do {
  realm = try Realm(configuration: configuration)
}
catch let error {
  // handle exception
}

// Throws `libc++abi.dylib: terminating with uncaught exception of type realm::RealmFileException: Unable to open a realm at path '.../private.realm': Realm file decryption failed.` when wrong encryption key is used. Expected it would be caught.