Extract table from NSAttributedString

Question

Suppose I have read NSAttributedString from a file (html or rtf) and in that file I clearly see several tables. Is there a way to extract those tables or at least find an NSRange that corresponds to the table? It would be ideal if I could somehow extract (array of) NSTextTableBlock,NSTextTable or NSTextBlock from NSAttributedString. But if that's not possible, then at least there should be a way to find NSRanges of table cells or something similar. Swift (possibly 4) is preferred but obj-c is fine too.

For example imagine such scenario:

let html =
"""
<table style="height: 51px;" width="147">
    <tbody>
        <tr>
            <td style="width: 65.5px;">a</td>
            <td style="width: 65.5px;">b</td>
        </tr>
        <tr>
            <td style="width: 65.5px;">c</td>
            <td style="width: 65.5px;">d</td>
        </tr>
    </tbody>
</table>
"""
var str = NSAttributedString(html: html.data(using: .utf8)!,    options: [:], documentAttributes: nil)!

and then I would like to do something more or less like this:

for table in str{
    for row in table{
        for cell in row{
            //do something
        }
    }
}

Answer 1

I found a bit naive solution to this problem but it works. You basically iterate over all characters in NSAttributedString, query their attributes and then check if among them is a NSParagraphStyle with a table.

This piece of code extracts array of NSTextTable from given location (remember that tables can be nested)

extension NSAttributedString{

func paragraphStyle(at index:Int)->NSParagraphStyle?{
    let key = NSAttributedStringKey.paragraphStyle
    return attribute(key, at: index, effectiveRange: nil) as! NSParagraphStyle?
}
func textBlocks(at index:Int)->[NSTextBlock]?{
    return paragraphStyle(at: index)?.textBlocks
}
func tables(at index:Int)->[NSTextTable]?{
    guard let tbs = textBlocks(at: index) else{
        return nil
    }
    var output = Set<NSTextTable>()
    for tb in tbs{
        if let t = tb as? NSTextTableBlock{
            output.insert(t.table)
        }
    }
    return Array(output)
}

}

And this could help you to collect all tables (except nested tables - in order to collect them too, you would have to run this function recursively inside every table):

extension NSAttributedString{

var outterTables:[NSTextTable]{
    var index = 0
    let len = length
    var output:[NSTextTable] = []
    while index < len{
        if let tab = outterTable(at: index){
            output.append(tab)
            index = range(of: tab, at: index).upperBound
        }else{
            index += 1
        }
    }
    return output
}

}