iOS parsing text similar to markdown

mraheel · Jan 26, 2013

I'm gonna try and create a simple iOS text parser, nothing complicated at all, I need it to be customisable, thats the reason I'm attempting this.

A markdown parser is great, but its meant as a publishing tool and is too extensive. I want something very similar in concept,

Forexample, Consider a text file with:

Code:

    A paragraph with with title with maybe a couple of lines without a title.


    Title
    -----
    A paragraph with a title.


    Title
    -----
    A paragraph with a title, this also includes bullet list.
       1. item0
       2. item1
       3. item2

Basically there are three "para" items in the above text file. I want to each of them parsed and added into an Array.

My question is, whats the best way to parse these items? How can I:

1. Separate each of those paras into items.
1. Check if item has a "title"
2. If it does, Separate the "Title" and paragraph text in each of those items.

Any comments is very very appreciated.

ArtOfWarfare · Jan 26, 2013

I'm not quite sure I understand what you're looking to do, but I think NSString's componentsSeperatedByString: method will prove useful to you.

PhoneyDeveloper · Jan 26, 2013

APIs to use for parsing something like this include:

Code:

NSScanner
NSString enumerateLinesUsingBlock:
NSString componentsSeparatedByString:
NSString componentsSeparatedByCharactersInSet:

Your parser needs to be a little state machine. It walks down the text line by line. It accumulates the lines in the current paragraph. It ends a paragraph with blank lines. It identifies titles by ... etc.

dejo · Jan 26, 2013

Also remember that iOS now has regular-expression support.

mraheel · Jan 27, 2013

Thanks for the input guys,

I got the basic idea, I'm wondering if thats the right way to go.

Code:

NSScanner
NSString enumerateLinesUsingBlock:
NSString componentsSeparatedByString:
NSString componentsSeparatedByCharactersInSet:

These APIs will do it, heres my routine:

1- Find sets of paragraph,
Divide paragraphs - [separated by string: @"\n\n"];

2- Go over each paragraph, check if @"\n---" exists, if it does, strip out title and text below it.

3. if the text has numbers with a period and a return @"\n" preceding it, and lots of them, its a numbered list, capture em, put them in an array.

Pretty much possible, except when the text does not follow specific pattern, which is pushing me toward NSRegularExpression as dejo rightly mentioned.

Any good guides on NSRegularExpression? Its really hard to understand.

Albright · Jan 27, 2013

If Markdown is too much, would you consider just using a subset of it? Or perhaps another markup syntax like Textile?

I really think that by rolling your own markup syntax and parser, you're unnecessarily complicating things and trying to solve a problem which has already been solved many different ways. Let the inevitable edge cases be somebody else's problem.

mraheel · Jan 28, 2013

Albright said:
If Markdown is too much, would you consider just using a subset of it? Or perhaps another markup syntax like Textile?

I really think that by rolling your own markup syntax and parser, you're unnecessarily complicating things and trying to solve a problem which has already been solved many different ways. Let the inevitable edge cases be somebody else's problem.

You are absolutely right. My goal was to create and learn, but i realise that maybe its not worth it.

Textile is exactly what I need, However, I cannot find an ObjC library.

ArtOfWarfare · Jan 28, 2013

mraheel said:
You are absolutely right. My goal was to create and learn, but i realise that maybe its not worth it.

Textile is exactly what I need, However, I cannot find an ObjC library.

There's a javascript one that you can use via a UIWebView:

http://stackoverflow.com/questions/2595871/textile-parsing-in-objective-c

Edit: Although the link seems to be broken?

mraheel · Jan 28, 2013

Well, the whole point of me doing this was Not to use a UIWebView. The data type didnt really require it.

dejo · Jan 28, 2013

mraheel said:
Well, the whole point of me doing this was Not to use a UIWebView.

And we were supposed to know this how?

ArtOfWarfare · Jan 28, 2013

mraheel said:
Well, the whole point of me doing this was Not to use a UIWebView. The data type didnt really require it.

What's the issue with a UIWebView? The JavaScript can be run locally on your device - there's no need for an Internet connection.

mraheel · Jan 30, 2013

dejo said:
And we were supposed to know this how?

My bad, should have made it clear before.

What's the issue with a UIWebView? The JavaScript can be run locally on your device - there's no need for an Internet connection.

yes, it can, my goal was to actually create NSObjects and use them as a dataset derived from simple textiles that could be used else where, not just a uiwebview.

Like if i can recognise a bullet list from a textfile, I can create an NSArray out of it, and use it in a uitableview.

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iOS parsing text similar to markdown

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