MPEdn

An EDN (Extensible Data Notation) Objective C I/O library for MacOS and iOS.

The library includes:

MPEdnParser, a parser for reading EDN and generating equivalent Cocoa data structures.
MPEdnWriter, which writes Cocoa data structures as EDN.

For most uses, parsing EDN is as simple as:

[@"{:a 1}" ednStringToObject];

Which returns the parsed object or nil on error.

And to generate EDN from a Cocoa object:

[myObject objectToEdnString];

See the headers for API docs.

Using It In Your Project

To use the library, use one of (in decreasing order of ease-of-use):

Install via CocoaPods: add pod 'MPEDN', '~> 1.0.0' to your Podfile.
Use a workspace containing your project and MPEdn as described here. You may also need to add the -all_load flag to the "Other Linker Flags" section of your project if the ednStringToObject and objectToEdnString category methods do not get linked in.
Generate libMPEdn.a using the supplied Xcode project and copy that and the .h files to your project.

EDN map <-> NSDictionary (but see [MPEdnParser newDictionary] to override).
EDN list or vector <-> NSArray (but see [MPEdnParser newArray] to override).
EDN set <-> NSSet (but see [MPEdnParser newSet] to override).
EDN string <-> NSString.
EDN float <-> NSNumber (numberWithDouble).
EDN int <-> NSNumber (numberWithLong). The N (bigint) suffix is not supported.
EDN decimal ('M' suffix, BigDecimal in Clojure) <-> NSDecimalNumber.
EDN boolean <-> NSNumber (numberWithBool).
EDN character <-> NSNumber (numberWithUnsignedChar).
EDN keyword <-> MPEdnKeyword. If the MPEdnWriter.useKeywordsInMaps property is true (the default is false as of 0.2), strings used as keys in NSDictionary will be output as keywords if possible. Note that strings and keywords never compare as equal, so this could get confusing when reading a dictionary from an external service that uses keywords: in general, prefer explicit use of keywords where possible.
EDN symbol <-> MPEdnSymbol.
EDN tagged values can be translated by tag reader/writer classes implementing MPEdnTaggedValueWriter and/or MPEdnTaggedValueReader (see MPEdnBase64Codec for an example). You can accept any tag regardless of whether there is a reader for it or not by setting the allowUnknownTags property on MPEdnParser, which will represent unknown tagged values with MPEdnTaggedValue instances. MPEdnWriter knows how to output MPEdnTaggedValue's which enables round-tripping of EDN with unknown tags.

Symbols would probably be better handled in future by resolving them to a mapped value, either through a symbol table or a user-defined callback.
Floats are output in full to avoid loss of precision.
Newlines in strings are output in their escaped form (\n rather than a raw 0x0a) even though the raw form is legal in order to make it straightforward to use generated EDN strings in line-oriented protocols.
The parser and writer fully support all Unicode code points in string values (i.e. both 'normal' characters and UTF-16 surrogate pairs), but not elsewhere. Adding general support would be straightforward, at the cost of some speed, but since EDN syntax is defined in terms of ASCII character classes it's not clear that using anything but ASCII outside of strings would be valid EDN in any case.

MPEdn is developed by Matthew Phillips (m@mattp.name). It is licensed under the same open source license as Clojure, the Eclipse Public License v1.0 .