antlr/doc/swift-target.md

ANTLR4 Language Target, Runtime for Swift

Usage

1. Install ANTLR4

The getting started guide should get you started.

2. create a Swift lexer or parser

This is pretty much the same as creating a Java lexer or parser, except you need to specify the language target, for example:

$ antlr4 -Dlanguage=Swift MyGrammar.g4

For a full list of antlr4 tool options, please visit the tool documentation page.

3. Get the Swift ANTLR runtime

You will find Swift runtime (framework project) in

antlr4/runtime/Swift 

4. Example

The example from here

(1). Hello.g4

grammar Hello;
r  : 'hello' ID ;          
ID : [a-z]+ ;              
WS : [ \t\r\n]+ -> skip ;  

(2). generate lexer/parser/visitor from Hello.g4 file

$ antlr4 -Dlanguage=Swift -visitor -o gen Hello.g4

in gen folder：

Hello.tokens
HelloBaseListener.swift
HelloBaseVisitor.swift
HelloLexer.swift
HelloLexer.tokens
HelloLexerATN.swift
HelloListener.swift
HelloParser.swift
HelloParserATN.swift
HelloVisitor.swift 

(3). make a custom listener

public class HelloWalker: HelloBaseListener{
    public override func enterR(_ ctx: HelloParser.RContext) {
        print( "enterR: " + ((ctx.ID()?.getText()) ?? ""))
    }

    public override func exitR(_ ctx: HelloParser.RContext) {
        print( "exitR  ")
    }
}

(4). call and run

add TestHello.txt

hello world

run:

import Antlr4

....

do {

	let textFileName = "TestHello.txt"
	if let textFilePath = Bundle.main.path(forResource: textFileName, ofType: nil) {
    	let lexer =  HelloLexer(ANTLRFileStream(textFilePath))
    	let tokens =  CommonTokenStream(lexer)
    	let parser = try HelloParser(tokens)
    	let tree = try parser.r()
    	let walker = ParseTreeWalker()
    	try walker.walk(HelloWalker(),tree)
	} else {
    	print("error occur: can not open \(textFileName)")
	}

}catch ANTLRException.cannotInvokeStartRule {
    print("error occur: CannotInvokeStartRule")
}catch ANTLRException.recognition(let e )   {
    print("error occur\(e)")
}catch {
    print("error occur")
}