This framework was developed for [Evergreen](https://github.com/brentsimmons/Evergreen) and is made available here for developers who just need the parsing code. It has no depencies that aren’t provided by the system.
To parse a feed, call `FeedParser.parse(parserData)`, which will return a [ParsedFeed](Feeds/ParsedFeed.swift). Also see related structs: `ParsedAuthor`, `ParsedItem`, `ParsedAttachment`, and `ParsedHub`.
However, if you do want to use a concrete parser directly, see [RSSInJSONParser](Feeds/JSON/RSSInJSONParser.swift), [JSONFeedParser](Feeds/JSON/JSONFeedParser.swift), [RSSParser](Feeds/XML/RSSParser.swift), and [AtomParser](Feeds/XML/AtomParser.swift).
(Note: if you want to write a feed reader app, please do! You have my blessing and encouragement. Let me know when it’s shipping so I can check it out.)
## How to parse OPML
Call `+[RSOPMLParser parseOPMLWithParserData:error:]`, which returns an `RSOPMLDocument`. See related objects: `RSOPMLItem`, `RSOPMLAttributes`, `RSOPMLFeedSpecifier`, and `RSOPMLError`.
## How to parse dates
Call `RSDateWithString` or `RSDateWithBytes` (see `RSDateParser`). These handle the common internet date formats. You don’t need to know which format.
## How to parse HTML
To get an array of `<a href=…` links from from an HTML document, call `+[RSHTMLLinkParser htmlLinksWithParserData:]`. It returns an array of `RSHTMLLink`.
To parse the metadata in an HTML document, call `+[RSHTMLMetadataParser HTMLMetadataWithParserData:]`. It returns an `RSHTMLMetadata` object.
To write your own HTML parser, see `RSSAXHTMLParser`. The two parsers above can serve as examples.
## How to parse HTML entities
When you have a string with things like `—` and `ë` and you want to turn those into the correct characters, call `-[NSString rsparser_stringByDecodingHTMLEntities]`. (See `NSString+RSParser.h`.)
## How to parse XML
If you need to parse some XML that isn’t RSS, Atom, or OPML, you can use `RSSAXParser`. Don’t subclass it — instead, create an `RSSAXParserDelegate`. See `RSRSSParser`, `RSAtomParser`, and `RSOPMLParser` as examples.
### Why use libXML2’s SAX API?
SAX is kind of a pain because of all the state you have to manage.
An alternative is to use `NSXMLParser`, which is event-driven like SAX. However, `RSSAXParser` was written to avoid allocating Objective-C objects except when absolutely needed. You’ll note use of things like `memcp` and `strncmp`.
Normally I avoid this kind of thing *strenuously*. I prefer to work at the highest level possible.
But my more-than-a-decade of experience parsing XML has led me to this solution, which —last time I checked, which was, admittedly, a few years ago —was not only fastest but also uses the least memory. (The two things are related, of course: creating objects is bad for performance, so this code attempts to do the minimum possible.)
All that low-level stuff is encapsulated, however. If you just want to parse one of the popular feed formats, see `FeedParser`, which makes it easy and Swift-y.
