Using Realm in iOS swift 4 - ios

Question

I am using Realm and it looks good.But I am confused here. Because I did not get how Realm is working and what is its structure of saving data.
I am basically an Android developer and you can say I am newbie in iOS. So in my mind I was thinking That there will be a main file of database. and then inside it, there will be different tables and in tables I can save data.
But I am very amazed that I saved data but It did not asked me for table name and I really do not know how to create table in it. AS in Java we have first create table then we reflect our model as row in that table in database. I am using following file to save Data in Realm . Please have a look and clear following confusions
tell me how realm works?
how the Table is created in realm ?
How to check if db is existed I mean if data is saved already?
How to check if any table let say (Country table) is already created so to retrieve data ??
and see the following class. It is basically a helper class.
public class DbHelper {
private init() {}
static let sharedDbHelper = DbHelper()
var realmObj = try! Realm()
/**
Generic function to create Object in the DB
*/
func save <T: Object> (_ obj : T){
do {
try realmObj.write {
realmObj.add(obj)
}
}catch{
print("DbHelperException","Create",error)
}
}
/**
Generic function to update Object in the DB
*/
func update <T: Object> (_ obj : T, with dictionary: [String : Any?]){
do{
try realmObj.write {
for (key,value) in dictionary{
obj.setValue(value, forKey: key)
}
}
}catch {
print("DbHelperException","Update",error)
}
}
/**
Generic function to delete Object in the DB
*/
func delete <T: Object> (_ obj : T){
do {
try realmObj.write {
realmObj.delete(obj)
}
}catch {
print("DbHelperException","Delete",error)
}
}
/**
Function to manage the error and post it
*/
func postDbError(_ error : Error) {
NotificationCenter.default.post(name: NSNotification.Name(""), object: error)
}
/**
Function to observe the error and post it
*/
func observeDbErrors(in Vc: UIViewController, completion: #escaping (Error?) -> Void) {
NotificationCenter.default.addObserver(forName: NSNotification.Name(""), object: nil, queue: nil) { (notification) in
completion(notification.object as? Error)
}
}
/**
Function to remove observer of the error
*/
func stopDbErrorObserver (in Vc: UIViewController ){
NotificationCenter.default.removeObserver(Vc, name: Notification.Name(""), object: nil)
}
}

Answer 1

I think all your questions are concerned with the same issue, you think that a Realm Database works using tables, however, this is not the case, instead a Realm Database uses Realms. They can be local (your case), in-memory, or synchronized.
A Realm can contain multiple kinds of objects, which would represent the tables you are thinking of.
If you want to have different tables, the solution would be to define multiple RealmObjects.
To check if your Realm doesn't contain any instance of a specific object you could do something like this: database.objects(YourRealmObject).isEmpty()

Answer 2

The equivalent to a "table" in Realm is a model that you define as a class . You can read about this here: https://realm.io/docs/swift/latest/#models
Here's an example that Realm provides:
class Dog: Object {
#objc dynamic var name = ""
#objc dynamic var owner: Person? // Properties can be optional
}
So in this case, Dog is your table name, and name and owner are your column names (each with a specific data type).