Sync data with ios swift local Database and server

Question

I am trying to build an iOS swift application that uses SQLITE and syncs it to my PHP backend server .

I can build API that reads and write data from server . I can read and write data with swift from server making HTTP requests .

What I am trying to accomplish here is : saving data to local database and sync it to the server database , the local database is user specific and the server database contains all users data .

Local DB

--------------------------
| maint item | due date | 
| abc        | 29-3-2018
| DNA        | 24-1-2017
| boy        | 17-2-2017
--------------------------

Server DB

---------------------------
| Maine item | due date | user 
| abc        | 29-3-2018| Jane 
| DNA        | 24-1-2017| Jane
| boy        | 17-2-2017| Jane
| amc        | 22-7-2017| cameleon

How can I achieve that in swift and if possible please post example project .

Will you send those rows of data as array of items in JSON format? — Paramasivan Samuttiram
– Paramasivan Samuttiram, Commented Apr 21, 2017 at 18:38

Damyan Todorov · Accepted Answer · 2019-04-15 07:58:05Z

1

There are a lot of scenarios, but I recommend this one:

Separate the layers of the project I recommend VIPER, Clean swift or ReSwift architecture.

After that your best friend will be the Interactor ( Thunk in ReSwift), there you will navigate the API and Database managers.

example :

If I have internet, download info from the API check If there is a similar object in the local database and present the new one. If the local is new update the API (or not .. :) ).

If I don't have internet show the local and update the date if the local one is changed...

Of course, there is no simple solution something more about the subject https://en.wikipedia.org/wiki/Eventual_consistency

edited Apr 15, 2019 at 7:58

answered Apr 21, 2017 at 19:07

Damyan Todorov

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1 Comment

Sameh Over a year ago

I was asking more of like a standard / simple way to do it . Like I thought it would have been done several times before and there's some sort of a standards example by the way I don't require SQLLite

A. Barone · Accepted Answer · 2017-04-21 18:45:08Z

0

You could use FMDB to handle SQLite, just add it to your podfile:

pod "FMDB"

then install:

pod install

and import it in your bridging header:

#import <FMDB/FMDB.h>

The documentation is in Objective-C, but it's quite easy to translate that in swift. For example:

import FMDB

let path = NSSearchPathForDirectoriesInDomains(.libraryDirectory, .userDomainMask, true)[0] + "/database.db"
let db = FMDatabase(path: path)
guard db.open() else {
            log.error("Unable to open database")
            return
}
db.executeStatements("CREATE TABLE ...")

Regarding the syncing process it's not so straightforward because you have to handle conflicts, unique IDs and so on.

If SQLite is not a requirement take a look at CouchDB or SyncDB.

I hope this will help you!

answered Apr 21, 2017 at 18:45

A. Barone

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2 Comments

A. Barone Over a year ago

Import the bridging header is not required if you use_frameworks! in your podfile. Then just import FMDB.

Sameh Over a year ago

Actually SQLITE is not a requirement I'm looking at your suggestions .

Community · Accepted Answer · 2017-05-23 12:25:52Z

You can look at http://github.com/groue/GRDB.swift.

It is a Swift SQLite library that ships with sample code for synchronizing a JSON document and a database table: https://github.com/groue/GRDB.swift/blob/master/Playgrounds/JSONSynchronization.playground/Contents.swift

The output of this demo playground is below. You can see that its algorithm is very efficient, and only applies the minimal amount of changes to the database:

-- Initial import {
--   "persons": [{
--     "id": 1,
--     "name": "Arthur"
--   }, {
--     "id": 2,
--     "name": "Barbara"
--   }, {
--     "id": 3,
--     "name": "Craig"
--   }, ]
-- }
SELECT * FROM persons ORDER BY id
INSERT INTO "persons" ("id", "name") VALUES (1,'Arthur')
INSERT INTO "persons" ("id", "name") VALUES (2,'Barbara')
INSERT INTO "persons" ("id", "name") VALUES (3,'Craig')

-- Import {
--   "persons": [{
--     "id": 2,
--     "name": "Barbie" (name is modified)
--   }, {
--     "id": 3,
--     "name": "Craig"  (not modified)
--   }, {
--     "id": 4,
--     "name": "Daniel" (new person)
--   }, ]
-- }    
SELECT * FROM persons ORDER BY id
DELETE FROM "persons" WHERE "id"=1
UPDATE "persons" SET "name"='Barbie' WHERE "id"=2
INSERT INTO "persons" ("id", "name") VALUES (4,'Daniel')

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