Interact with Swift on Pharo

by iOS Example

SwiftPlayground-Pharo

Run Swift with the Pharo Swift Playground, interoperate with Pharo, inspect output and Swift ASTs.

Installation

  1. Install and setup the Swift tools for your environment:

  2. In a Playground, evaluate:

    Metacello new
  repository: 'github://brackendev/SwiftPlayground-Pharo';
  baseline: 'SwiftPlayground';
  onConflict: [ :ex | ex useIncoming ];
  onUpgrade: [ :ex | ex useIncoming ];
  onDowngrade: [ :ex | ex useLoaded ];
  ignoreImage;
  load.

Usage

Swift Playground

Write, compile, run, and inspect output of Swift code via the Swift Playground (accessible via the Tools menu).

Important contextual menu items:
  • Do it – Compile and run the selected Swift code
  • Inspect it – Compile and run the selected Swift code, inspect it
  • Print it – Compile and run the selected Swift code, print it (TODO)

Additionally, the contextual menu item, Inspect AST, returns the Swift AST for the selected Swift code. For example, print("Hello, World!") returns:

(import_decl range=[Swift:1:1 - line:1:8] 'Foundation')
  (top_level_code_decl range=[Swift:2:1 - line:2:22]
    (brace_stmt range=[Swift:2:1 - line:2:22]
      (call_expr type='<null>' arg_labels=_:
        (unresolved_decl_ref_expr type='<null>' name=print function_ref=unapplied)
        (paren_expr type='<null>'
          (string_literal_expr type='<null>' encoding=utf8 value="Hello, World!" builtin_initializer=**NULL** initializer=**NULL**)))))

Inline Swift

Outside of the Swift Playground, Swift code can be executed within Pharo code by using the runSwift string class extension. For example:

API Reference

Swift Output and ASTs

Pharo class extension methods can be used to compile, run, and view the AST of Swift code.

String class extension: runSwift

Returns a string representation of a Swift object from Swift code. Use Swift's print function within the Swift code for output to Pharo. For example:

swiftString := 'The five boxing wizards jump quickly' asLowercase asSwiftString.
('let (lowercased, alphabet) = (Set(', swiftString, '), "abcdefghijklmnopqrstuvwxyz")
print("\(!alphabet.contains { !lowercased.contains($0) })")') runSwift.
"Returns 'true'"

Tip: Simple Swift code does not require Swift's print function. For example:

'Array("ABCDE")' runSwift.
"Returns '["A", "B", "C", "D", "E"]'"

swiftArray := #(1 2 3 4 5) asSwiftArray.
(swiftArray, '.map{$0 * $0}.reduce(0, +)') runSwift.
"Returns '55'"

String class extension: swiftAST

Returns the Swift AST of Swift code.

Pharo Object to Swift String Serialization

Pharo class extension methods can be used as quick helpers to serialize Pharo objects to Swift psuedo-objects (string representations of Swift objects). For example, 'Hello, World!' asSwiftString returns '"Hello, World!"'.

In the code below, notice the usage of sentence, asSwiftString, and the swiftCode string concatenation:

sentence := 'The five boxing wizards jump quickly' asLowercase asSwiftString.
swiftCode := ('
// Determine a pangram
let (sentenceSet, alphabet) = (Set(', sentence, '), "abcdefghijklmnopqrstuvwxyz")
print(!alphabet.contains {
  !sentenceSet.contains($0)
})
').
swiftCode runSwift.
"Returns 'true'"

The following extension methods have been implemented (with examples). The examples are also availabe via the SPExamples object.

Array class extension: asSwiftArray

Returns a string representation of a Swift object. Currently only handles one depth of booleans, numbers, and strings.

#(1 'A' 2 true 3 false) asSwiftArray.
"Returns '[1,"A",2,true,3,false]'"

Boolean class extension: asSwiftBoolean

Returns a string representation of a Swift object.

true asSwiftBoolean.
"Returns 'true'"

Dictionary class extension: asSwiftDictionary

Returns a string representation of a Swift object. Currently only handles one depth of booleans, numbers, and strings.

(Dictionary newFrom: {(1 -> 2). ('A' -> 3). (4 -> 'B'). (5 -> true). (false -> 'C'). ('D' -> 'E')})  asSwiftDictionary.
"Returns '[1:2,"A":3,4:"B",5:true,"D":"E",false:"C"]'"

String class extension: asSwiftString

Returns a string representation of a Swift object.

'Hello, World!' asSwiftString.
"Returns '"Hello, World!"'"

Swift Response String to Pharo Object Deserialization

(TODO)

Imports

The Apple Foundation framework is imported into Swift code automatically. To use other Apple frameworks with Swift code, use the Swift import directive as needed.

Asynchronous Swift Code

To prevent asynchronous Swift code from exiting too early, use the Swift dispatchMain() function to never return and use the Swift exit() function to exit where appropriate.

For example, in the Swift code below, a Swift URLRequest network request session is started and then followed by dispatchMain() so the program does not prematurely exit. In the session response closure exit(0) is then called to exit the program.

let sessionConfig = URLSessionConfiguration.default
let session = URLSession(configuration: sessionConfig, delegate: nil, delegateQueue: nil)

var url = URL(string: "https://www.gravatar.com/4f64c9f81bb0d4ee969aaf7b4a5a6f40.json")
var request = URLRequest(url: url!)
request.httpMethod = "GET"

let task = session.dataTask(with: request, completionHandler: { data, response, error in
    if let uError = error {
        print(uError.localizedDescription) // Returns error string
    } else if let uData = data, let string = String(data: uData, encoding: String.Encoding.utf8) {
        print(string) // Returns response string
    }
    exit(0) // Exit after asynchronous work is complete
})
task.resume()

session.finishTasksAndInvalidate() // Start the network request session
dispatchMain() // Prevent premature exit

TODO

  • [ ] Swift Playground Print it
  • [ ] Swift Playground syntax highlighting
  • [ ] Swift response string to Pharo object deserialization
  • [ ] Move documentation to the wiki
  • [ ] Move to Spec2

GitHub