It's pretty straightforward to convert a string to a regex:
let regex = try! Regex("foo")
But if I try to get the string back out of the regex, instead of foo, I get something like:
_StringProcessing.Regex<_StringProcessing.AnyRegexOutput>(program: _StringProcessing.Regex<_StringProcessing.AnyRegexOutput>.Program)
Mirrors are of marginal help here. It takes several levels of reflection to get anywhere:
let regexMirror = Mirror(reflecting: regex)
let program = regexMirror.children.first!.value // runtime type: Regex<AnyRegexOutput>.Program
let programMirror = Mirror(reflecting: program)
print(Array(programMirror.children))
[(label: Optional("tree"), value: _StringProcessing.DSLTree(root: _StringProcessing.DSLTree.Node.convertedRegexLiteral(_StringProcessing.DSLTree.Node.concatenation([_StringProcessing.DSLTree.Node.convertedRegexLiteral(_StringProcessing.DSLTree.Node.atom(_StringProcessing.DSLTree.Atom.char("f")), _StringProcessing.DSLTree._AST.ASTNode(ast: ｢f｣)), _StringProcessing.DSLTree.Node.convertedRegexLiteral(_StringProcessing.DSLTree.Node.atom(_StringProcessing.DSLTree.Atom.char("o")), _StringProcessing.DSLTree._AST.ASTNode(ast: ｢o｣)), _StringProcessing.DSLTree.Node.convertedRegexLiteral(_StringProcessing.DSLTree.Node.atom(_StringProcessing.DSLTree.Atom.char("o")), _StringProcessing.DSLTree._AST.ASTNode(ast: ｢o｣))]), _StringProcessing.DSLTree._AST.ASTNode(ast: (｢f｣,｢o｣,｢o｣))))), (label: Optional("compileOptions"), value: _StringProcessing._CompileOptions(rawValue: 0)), (label: Optional("_loweredProgramStorage"), value: nil)]
This is something that gives the appearance of being parseable, but it's full of private types and things I don't particularly care about.
Is there a simple way to get the string representation of a regex?
There is an API to do this, but the bad news is that it’s currently private:
let regex = /[a-z]/
let pattern: String? = regex._literalPattern
If you’re not forced to deal with Apple’s App Stores, it works great. See the declaration here.