GitHub - IBM-Swift/Swift-Kuery-PostgreSQL: PostgreSQL plugin for Swift-Kuery fra...
source link: https://github.com/IBM-Swift/Swift-Kuery-PostgreSQL
Go to the source link to view the article. You can view the picture content, updated content and better typesetting reading experience. If the link is broken, please click the button below to view the snapshot at that time.
README.md
Swift-Kuery-PostgreSQL
PostgreSQL plugin for the Swift-Kuery framework. It enables you to use Swift-Kuery to manipulate data in a PostgreSQL database.
PostgreSQL client installation
To use Swift-Kuery-PostgreSQL you must have the appropriate PostgreSQL C-language client installed.
macOS
$ brew install postgresql
Linux
$ sudo apt-get install libpq-dev
Usage
Add dependencies
Add the SwiftKueryPostgreSQL
package to the dependencies within your application’s Package.swift
file. Substitute "x.x.x"
with the latest SwiftKueryPostgreSQL
release.
.package(url: "https://github.com/IBM-Swift/Swift-Kuery-PostgreSQL.git", from: "x.x.x")
Add SwiftKueryPostgreSQL
to your target's dependencies:
.target(name: "example", dependencies: ["SwiftKueryPostgreSQL"]),
Import package
import SwiftKueryPostgreSQL
Using Swift-Kuery-PostgreSQL
First create an instance of Swift-Kuery-PostgreSQL
by calling:
let connection = PostgreSQLConnection(host: host, port: port, options: [ConnectionOptions]?)
Where:
- host and port are the host and the port of PostgreSQL
- ConnectionOptions an optional set of:
- options - command-line options to be sent to the server
- databaseName - the database name
- userName - the user name
- password - the user password
- connectionTimeout - maximum wait for connection in seconds. Zero or not specified means wait indefinitely.
For more details refer to the PostgreSQL manual.
Alternatively, call:
let connection = PostgreSQLConnection(url: URL(string: "Postgres://\(username):\(password)@\(host):\(port)")!))
To establish a connection call:
PostgreSQLConnection.connect(onCompletion: (QueryError?) -> ())
You now have a connection that can be used to execute SQL queries created using Swift-Kuery.
Getting Started with Swift-Kuery-PostgreSQL locally
Install PostgreSQL server
Mac
brew install postgresql
Ubuntu Linux
sudo apt-get install postgresql postgresql-contrib
Make sure you have the database running. This installation should have also installed two applications we need, namely (createdb and psql) which will be used as clients to your locally running PostgreSQL.
Create a database
Let's create a database called school
:
createdb school
Create the tables
Now, let's create the tables we need for this example.
Use the interative psql
client to open the database we created:
$ psql school
psql (9.5.4)
Type "help" for help.
school=#
First, create the student table:
CREATE TABLE student ( studentId BIGSERIAL PRIMARY KEY, name varchar(100) NOT NULL CHECK (name <> '') );
Next, create the grades table:
CREATE TABLE grades ( key BIGSERIAL PRIMARY KEY, studentId integer NOT NULL, course varchar(40) NOT NULL, grade integer );
Populate the tables
First the students table:
INSERT INTO student VALUES (1, 'Tommy Watson'); INSERT INTO student VALUES (2, 'Fred Flintstone');
And then the grades table:
INSERT INTO grades (studentId, course, grade) VALUES (1, 'How to build your first computer', 99); INSERT INTO grades (studentId, course, grade) VALUES (2, 'How to work at a rock quarry', 71);
Use Swift-Kuery
Now we are set to connect to our database from Swift and use Swift-Kuery to query the data into our Swift application.
Create simple Swift executable
First create a directory for our project and then initialize it.
$ mkdir swift-kuery-play
$ cd swift-kuery-play
$ swift package init --type executable
Creating executable package: swift-kuery-play
Creating Package.swift
Creating README.md
Creating .gitignore
Creating Sources/
Creating Sources/swift-kuery-play/main.swift
Creating Tests/
$
Now, add Swift-Kuery-PostgreSQL as a dependency for our project, this will automatically pull in Swift-Kuery.
Edit Package.swift
to contain the following, substituting "x.x.x"
with the latest Kitura
and Swift-Kuery-PostgreSQL
releases.
// swift-tools-version:4.0 import PackageDescription let package = Package( name: "swift-kuery-play", dependencies: [ .package(url: "https://github.com/IBM-Swift/Kitura.git", from: "x.x.x"), .package(url: "https://github.com/IBM-Swift/Swift-Kuery-PostgreSQL", from: "x.x.x") ], targets: [ .target( name: "swift-kuery-play", dependencies: ["Kitura", "SwiftKueryPostgreSQL"]), ] )
Now, edit your main.swift
file to contain:
import SwiftKuery import SwiftKueryPostgreSQL import Kitura let router = Router() class Grades : Table { let tableName = "grades" let key = Column("key") let course = Column("course") let grade = Column("grade") let studentId = Column("studentId") } let grades = Grades() let connection = PostgreSQLConnection(host: "localhost", port: 5432, options: [.databaseName("school")]) func grades(_ callback: @escaping (String) -> Void) -> Void { connection.connect() { error in if let error = error { callback("Error is \(error)") return } else { // Build and execute your query here. // First build query let query = Select(grades.course, grades.grade, from: grades) connection.execute(query: query) { result in if let resultSet = result.asResultSet { var retString = "" for title in resultSet.titles { // The column names of the result. retString.append("\(title.padding(toLength: 35, withPad: " ", startingAt: 0))") } retString.append("\n") for row in resultSet.rows { for value in row { if let value = value { let valueString = String(describing: value) retString.append("\(valueString.padding(toLength: 35, withPad: " ", startingAt: 0))") } } retString.append("\n") } callback(retString) } else if let queryError = result.asError { // Something went wrong. callback("Something went wrong \(queryError)") } } } } } router.get("/") { request, response, next in grades() { resp in response.send(resp) next() } } Kitura.addHTTPServer(onPort: 8080, with: router) Kitura.run()
Now build the program and run it:
$ swift build
$ .build/debug/swift-kuery-play
Now open a web page to http://localhost:8080 and you should see:
course grade
How to build your first computer 99
How to work at a rock quarry 71
Now we can change our query line and see different results.
Change the line:
let query = Select(grades.course, grades.grade, from: grades)
to
let query = Select(grades.course, grades.grade, from: grades) .where(grades.grade > 80)
and we should only see grades greater than 80:
course grade
How to build your first computer 99
Another possibility is to use QueryResult.asRows
that returns the result as an array of dictionaries where each dictionary represents a row of the result with the column title as the key.
Change your grades
function as follows:
func grades(_ callback: @escaping (String) -> Void) -> Void { connection.connect() { error in if let error = error { callback("Error is \(error)") return } else { let query = Select(grades.course, grades.grade, from: grades) connection.execute(query: query) { result in if let rows = result.asRows { var retString = "" for row in rows { for (title, value) in row { if let value = value { retString.append("\(title): \(value) ") } } retString.append("\n") } callback("\(retString)") } else if let queryError = result.asError { callback("Something went wrong \(queryError)") } } } } }
At http://localhost:8080 you should see:
grade: 99 course: How to build your first computer
grade: 71 course: How to work at a rock quarry
API Documentation
For more information visit our API reference.
Community
We love to talk server-side Swift, and Kitura. Join our Slack to meet the team!
License
This library is licensed under Apache 2.0. Full license text is available in LICENSE
Recommend
About Joyk
Aggregate valuable and interesting links.
Joyk means Joy of geeK