Parsing Excel Spreadsheets with Swift's Codable Protocols
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Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#2First off: awesome work!
Correctly reading the data from XLSX is a lot more complex than described or implemented here, mostly because Excel is so robust in reading files and there are many sloppy writers. If you're interested, there's a many-thousand page ECMA-376 specification: https://www.ecma-international.org/publications/standards/Ec...
- to correctly get the first worksheet, you actually need to parse the workbook.xml file and look into the sheets array to find the corresponding relationship IDs. This is explained in section 18.2.20 (page 1579 in the part 1 PDF). iOS Numbers used to write worksheets in the opposite order, which messes up the naive attempt to read the relationships file in order.
- the attribute "s" in a cell is an index into the styles table, while the cell type "s" corresponds to the shared string table. If you're curious, its in section 18.1.3.4 (page 1604 in the part 1 PDF)
PS: We build and maintain parsers and writers for spreadsheets in JavaScript (https://github.com/SheetJS/js-xlsx/ is our most popular project), including a CLI script to convert files to CSV. Some of our users use JSC in the context of Swift applications, ingesting data in JS and returning a CSV for further processing in Swift.
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#3First off: awesome work! Correctly reading the data from XLSX is a lot more complex than described or implemented here, mostly because Excel is so robust in reading files and there are many sloppy writers. If you're interested, there's a many-thousand page ECMA-376 specification: https://www.ecma-international.org/publications/standards/Ec... - to correctly get the first worksheet, you actually need to parse the work…
> there's a many-thousand page ECMA-376
Honestly, I'd love to see if there are organizational tips on managing (and using!) a document that large.
I feel like technical writing is the closest to coding we get in plain languages, but there are still critical differences. (technical writing is trying to give instruction to a human, while coding is giving instructions to code while giving a lot more context and description to a human). Specs cross this line a bit more - it's giving descriptions to a human with the intention of giving instructions)
Unfortunately, while I can find good code and bad code, I tend to find bad specs and WORSE specs. I can see progress (the various HTML5 and related specs are vastly better than previous versions, for example), but anytime I go in with a question (which is admittedly rare) I spend a lot of time finding the salient part compared to related-but-missing-the-vital-piece part, which is actually the exact same problem that I think the most common problem in maintainable code: making it easy to not only know how, but WHERE.
Are there lessons from specs we can learn? Do the good ones have some sort of "concept" section that makes the reading of it easier? Does each subsection do that?
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#4First off: awesome work! Correctly reading the data from XLSX is a lot more complex than described or implemented here, mostly because Excel is so robust in reading files and there are many sloppy writers. If you're interested, there's a many-thousand page ECMA-376 specification: https://www.ecma-international.org/publications/standards/Ec... - to correctly get the first worksheet, you actually need to parse the work…
Looks like this guy excels in his field.
Jokes aside, I can't fathom having to consult a thousand page manual to deal with this stuff, I can barely read the README.md for a framework that I want to include in my project.
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#5First off: awesome work! Correctly reading the data from XLSX is a lot more complex than described or implemented here, mostly because Excel is so robust in reading files and there are many sloppy writers. If you're interested, there's a many-thousand page ECMA-376 specification: https://www.ecma-international.org/publications/standards/Ec... - to correctly get the first worksheet, you actually need to parse the work…
> there's a many-thousand page ECMA-376 Honestly, I'd love to see if there are organizational tips on managing (and using!) a document that large. I feel like technical writing is the closest to coding we get in plain languages, but there are still critical differences. (technical writing is trying to give instruction to a human, while coding is giving instructions to code while giving a lot more context and descript…
The advice is that it should only exist in machine-readable form and the reason why Microsoft does it this way is to ensure lock-in. See also MSSQL, for which there exists no complete machine-readable spec ANYWHERE (as far as I could tell when I spent 2 days looking a few years ago).
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#6The Codable protocol in Swift is game-changing. Max Howell (homebrew author) recently started a series of articles[1] in which he used Codable structs as the shared data model in both the backend and frontend of his new app Canopy. Even though communication is through HTTP and JSON, he never even has to touch it.
[1] - https://medium.com/@mxcl/server-side-swift-making-canopy-2ed...
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#7First off: awesome work! Correctly reading the data from XLSX is a lot more complex than described or implemented here, mostly because Excel is so robust in reading files and there are many sloppy writers. If you're interested, there's a many-thousand page ECMA-376 specification: https://www.ecma-international.org/publications/standards/Ec... - to correctly get the first worksheet, you actually need to parse the work…
> there's a many-thousand page ECMA-376 Honestly, I'd love to see if there are organizational tips on managing (and using!) a document that large. I feel like technical writing is the closest to coding we get in plain languages, but there are still critical differences. (technical writing is trying to give instruction to a human, while coding is giving instructions to code while giving a lot more context and descript…
I wrote an XLSX(spreadsheet) writer in golang a few years ago and still maintain it. I also deal with a bunch of other several hundred to thousand page docs semi regularly and the best advice I have is to make use of the index, bookmarking pages, and a ton of cmd+f searching for various keywords.
I was talking with a lawyer friend the other day who confirmed a good index is really a must for long documents.
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#8Earlier quoted context omitted.
> there's a many-thousand page ECMA-376 Honestly, I'd love to see if there are organizational tips on managing (and using!) a document that large. I feel like technical writing is the closest to coding we get in plain languages, but there are still critical differences. (technical writing is trying to give instruction to a human, while coding is giving instructions to code while giving a lot more context and descript…
The advice is that it should only exist in machine-readable form and the reason why Microsoft does it this way is to ensure lock-in. See also MSSQL, for which there exists no complete machine-readable spec ANYWHERE (as far as I could tell when I spent 2 days looking a few years ago).
[deleted]
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#9Earlier quoted context omitted.
> there's a many-thousand page ECMA-376 Honestly, I'd love to see if there are organizational tips on managing (and using!) a document that large. I feel like technical writing is the closest to coding we get in plain languages, but there are still critical differences. (technical writing is trying to give instruction to a human, while coding is giving instructions to code while giving a lot more context and descript…
The advice is that it should only exist in machine-readable form and the reason why Microsoft does it this way is to ensure lock-in. See also MSSQL, for which there exists no complete machine-readable spec ANYWHERE (as far as I could tell when I spent 2 days looking a few years ago).
>lock-in
A company that spends millions of dollars employing technical writers to publicly document a format probably isn't conspiring to keep that format secret. Maybe the macaronis aren't the shape you wanted but you got the macaronis.
Re: Parsing Excel Spreadsheets with Swift's Codable Protocols
#10First off: awesome work! Correctly reading the data from XLSX is a lot more complex than described or implemented here, mostly because Excel is so robust in reading files and there are many sloppy writers. If you're interested, there's a many-thousand page ECMA-376 specification: https://www.ecma-international.org/publications/standards/Ec... - to correctly get the first worksheet, you actually need to parse the work…
I appreciate such detailed feedback, thank you! Parsing of workbook.xml is implemented in the library itself in `parseWorksheetPaths` function I mentioned it briefly in the article, but decided to omit it as main focus was on Codable protocols.
I will definitely update the "s" attribute parsing to have a more sensible name. Will also link to the standard from the README file, although not sure that will help with a document of this size.