How to show a struct in html

I have the following code:

using Parameters

const BOLD   = "\e[1m"
const RED    = "\033[31;1m"
const GREEN  = "\033[32;1m"
const NORMAL = "\e[0m"

@with_kw mutable struct ChargerResult
    search_strings = String["No buffer space", "CAN1 Error"]
    frequency      = Int64[0, 0]
end, res::ChargerResult) = begin
    println("\n\n", BOLD, "Charger log(s):\n", NORMAL)
    for i in 1:length(res.frequency)
        if res.frequency[i] == 0
            println(io, GREEN, "Message: \"$(res.search_strings[i])\" not found!", NORMAL)
            println(io, RED, "Message: \"$(res.search_strings[i])\" found $(res.frequency[i]) times!", NORMAL)

res = ChargerResult()

This allows me to print a struct of type ChargerResult with colors on the command line.

Now I also want to have a similar html representation of this struct.

How can I achieve that?

Can I write different show methods for console and for html representation?

You can pass a MIME type as the second argument to show. By default it’s text/plain i.e. plaintext, so your method above applies to plaintext console output. You can write a method for the text/html MIME type separately, like:, ::MIME"text/html", res::ChargerResult) = begin
           println("<br> <strong>Charger log(s):</strong> <br>", NORMAL)
           for i in 1:length(res.frequency)
               if res.frequency[i] == 0
                   println(io, "<span style=\"color: #270\">Message: \"$(res.search_strings[i])\" not found!</span>")
                   println(io, "<span style=\"color: #D8000C\">Message: \"$(res.search_strings[i])\" found $(res.frequency[i]) times!</span>")

(Untested, and sort of a direct translation of the commandline output version - you might want fancier/more idiomatic HTML in the actual code.)

Separate from your question about HTML output, which was answered above (and is covered in the manual section on pretty-printing), is there a reason you’re not using printstyled(io, s, bold=true) here?

Even if you do need to print formatting codes directly for some reason in your show, you should first check get(io, :color, false) to see whether the io stream supports the ANSI formatting escapes. The printstyled function will do this for you.

1 Like

Thank you, I did not know the printstyled function…

Thank you! But how can I print the html version to a file or to a string after adding the new show method?

Call it? show(io, "text/html", mystruct)

The difference between print and show is still not clear to me… Does print also calls show in the end?

By default, yes, print(io, x) calls show(io, x), the 2-argument show. However, there are some types for which it is different, e.g. for strings:

julia> show("foo\nbar")
julia> print("foo\nbar")

This is explained in the documentation for Base.print.


There’s also this 2020 JuliaCon talk:

An abstract of the talk, with a link to the slides used, is at: