share open connection

[AMBIENTE1]

Hi there,
in my swift project I call an example right at the beginning:

do {
var configuration = PostgresClientKit.ConnectionConfiguration()
configuration.host = "127.0.0.1"
configuration.database = "example"
configuration.user = "bob"
configuration.credential = .scramSHA256(password: "welcome1")

let connection = try PostgresClientKit.Connection(configuration: configuration)
let text = "SELECT start();"
try connection.prepareStatement(text: text).execute()

} catch {
print(error)
}

I need the connection not to be terminated and continue in another function:

func test() {
do {
let text = "SELECT * FROM foo();"
try connection.prepareStatement(text: text).execute(). // error: Cannot find 'connection' in scope
} catch {
print(error)
}

My problem: I don't know how set "connection" as global var
Can you please advise me how to solve this?

[pitfield]

This is a general programming question that gets into object-oriented design. So you might want to consult Apple's Swift tutorial or other resources on the web. There are many approaches to do what you want. Here is one way:

• create a Swift type (a class or struct)
• in that type, add a stored property of type Connection
• in that type, add an initializer that sets that stored property
• move your test() function into that type

[AMBIENTE1]

Thank you for answer. I will try to ask differently.
The question is: How declare variable for connection = ???
then use: connection = try PostgresClientKit.Connection(configuration: configuration)
and after I can use anywhere in project: try connection.prepareStatement(text: text).execute()

[AMBIENTE1]

I tried use struct, but still I have problem with declare conn - Value of type '[conn]' has no member 'prepareStatement'
Any idea?

import UIKit
import PostgresClientKit

struct conn {
let conn : Connection
}
var myconnection = conn

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()

    do {
        var configuration = PostgresClientKit.ConnectionConfiguration()
        configuration.host = "127.0.0.1"
        configuration.database = "example"
        configuration.user = "bob"
        configuration.credential = .scramSHA256(password: "welcome1")

        let aaa = try PostgresClientKit.Connection(configuration: configuration)
        let bbb = conn ( conn: aaa)
        myconnection.append(bbb)
        
        let text = "SELECT start();"
        try myconnection.prepareStatement(text: text).execute()
        
        
    } catch {
        print(error) // better error handling goes here
    }
    
    
}

[AMBIENTE1]

Uff, try myconnection[0].conn.prepareStatement(text: text).execute()
my work is done :)

[AMBIENTE1]

I'm sorry, my problem is still not resolved. My function start() opens session in Postgres database and I need to make this session still open. I checked the function prepareStatement, where is written "Any previous Cursor for this Connection is closed.". Is there a solution to keep the session open?

[pitfield]

Please keep the discussion in this issue, rather than opening a new issue.

[pitfield]

Here is my understanding of what you want to do: You want to create a connection, and then be able to use that connection in various places in your application.

Here is a simple way to do this:

struct Database {

    private static var conn: Connection? = nil

    static func connection() throws -> Connection {

        if conn == nil {
            var configuration = PostgresClientKit.ConnectionConfiguration()
            configuration.host = "127.0.0.1"
            configuration.database = "example"
            configuration.user = "bob"
            configuration.credential = .scramSHA256(password: "welcome1")

            conn = try Connection(configuration: configuration)
        }
    
        return conn!
    }
}

func test() {
    do {
        let text = "SELECT * FROM weather;"
        let cursor = try Database.connection().prepareStatement(text: text).execute()
        // ...and process the results
    } catch {
        print(error)
    }
}

With this simple approach, you need to ensure that only one thread uses the connection at a time, and you need to handle the connection dying, for example because of a transient network issue.

Here is a more sophisticated approach:

https://github.com/pitfield/PostgresClientKit-iOS-Example

This uses a ConnectionPool. The README describes the benefits of doing this.

[AMBIENTE1]

Thank you so much for the solution!!