Received MethodError when cleaning String - julia

Question

I have data in a .txt file that looks like this:
04:31 Yuri Kane feat Jeza – Love Comes (Original Mix) [PREMIER]
25:31 Heatbeat & Quilla – Secret (Original Mix) [ARMADA CAPTIVATING]
All of them have this pattern:
00:00 artist - title [studio]
I want to remove the time stamp and the studio, so the output looks like this:
1. Yuri Kane feat Jeza – Love Comes (Original Mix)
Here is what I tried:
function remove_time_from(str::String)
return last(split(str,"0 "))
end
function remove_url(str::String)
return first(rsplit(str,"["))
end
function main()
tracks = String[]
local number = 0
for line in eachline("track-list.txt")
number += 1
removed_time = remove_time_from(line)
cleaned = remove_url(removed_time)
push!(tracks,"$number.$cleaned")
end
open("track-list-cleaned.txt", "w") do io
for line in tracks
write(io, "$line\n")
end
end
end
main()
but it returns:
MethodError: no method matching remove_url(::SubString{String})

Answer 1

When you use the function remove_time_from() it uses first() which returns a SubString{String}:
track = "04:31 Yuri Kane feat Jeza – Love Comes (Original Mix) [PREMIER]"
println(typeof(remove_time_from(track))) # Output: SubString{String}
You have 2 ways to fix it:
Have both remove_time_from() and remove_url() convert the SubString to String before returning it. This way, no matter which function you use first, you'll get a String:
return convert(String,last(split(str,"0 ")))
Use AbstractString instead of String as the function parameter, because SubString is a subtype of AbstractString:
println(SubString <: AbstractString) # Output: true
This way, no matter which function you use first, it would accept a String (the variable type of line) or SubString (the type you end up with after using one of the functions).
Suggestions:
Using split(str,"0 ") won't remove the time stamp:
last(split("04:31 Yuri Kane feat Jeza – Love Comes (Original Mix) [PREMIER]", "0 "))
Output: 04:31 Yuri Kane feat Jeza – Love Comes (Original Mix) [PREMIER]
What you need is chop() and you can specify how many characters to ignore from the head, so in this case 5 (includes the leading whitespace).
chop(str, head = 5)
You don't need to read in the lines, clean it, and then store it in a Vector to write later. You can clean it (do it in one line), and write it out to the file:
open("track-list-cleaned.txt", "w") do io
for line in eachline("track-list.txt")
number += 1
cleaned = (remove_url(remove_time_from(line)))
write(io, "$number.$cleaned\n")
end
end
Use enumerate() to number the lines as you're reading them in:
for (number,line) in enumerate(eachline("track-list.txt"))
Code:
# Using the assignment form because each function has only one line.
remove_time_from(str::AbstractString) = chop(str, head = 5)
remove_url(str::AbstractString) = first(rsplit(str," https"))
function main()
open("track-list-cleaned.txt", "w") do io
for (number,line) in enumerate(eachline("track-list.txt"))
cleaned = strip(remove_url(remove_time_from(line)))
write(io,"$number.$cleaned\n")
end
end
end
main()