PostgresClientKit-iOS-Example

Demonstrates use of PostgresClientKit in an iOS app.

This simple iOS app displays historical weather information for a user-specified city. It uses the weather table in the Postgres tutorial.

The app is structured as an Xcode project the consumes packages (including PostgresClientKit) from Swift Package Manager.

Using

First, use psql to create the weather table and insert a few rows.

CREATE TABLE weather (
    city            varchar(80),
    temp_lo         int,           -- low temperature
    temp_hi         int,           -- high temperature
    prcp            real,          -- precipitation
    date            date
);

INSERT INTO weather
    VALUES ('San Francisco', 46, 50, 0.25, '1994-11-27');

INSERT INTO weather (city, temp_lo, temp_hi, prcp, date)
    VALUES ('San Francisco', 43, 57, 0.0, '1994-11-29');
    
INSERT INTO weather (date, city, temp_hi, temp_lo)
    VALUES ('1994-11-29', 'Hayward', 54, 37);

Then, open the provided Xcode project.

open PostgresClientKit-iOS-Example.xcodeproj

In Xcode, open the Environment.json file and set its properties to values appropriate for your Postgres server:

• host
• port
• ssl
• database

In this simple example, the Postgres username and password are hardcoded in AppDelegate.swift. Set these values for your environment.

let model = Model(environment: Environment.current, user: "bob", password: "welcome1")

Choose a simulator and run the app. You should see historical weather information for San Francisco (assuming the weather table contains the sample data from the Postgres tutorial). Logging appears in the Xcode console. Try changing the city to Hayward and tapping Show.

To run on a physical device, select the PostgresClientKit-iOS-Example project in the project navigator, then select the PostgresClientKit-iOS-Example target in the editor, and set the development team to use for code signing.

Implementation notes

Model.swift encapsulates the interaction with the Postgres server.

A connection pool is created containing, at most, one connection. Although this application doesn't need more than one connection, using a connection pool provides several benefits:

• It creates the connection lazily.
• It automatically re-creates the connection if an unrecoverable connection error occurs.
• It performs database operations on a background thread

If the app moves to the background, the connection pool is closed and re-created (see sceneDidEnterBackground(_:) in SceneDelegate). If the app later re-enters the foreground, the new connection pool will lazily create a new connection.