I have a piece of lua code (executing in Corona):
local loginstr = "emailAddress={email} password={password}"
print(loginstr:gsub( "{email}", "[email protected]" ))
This code generates the error:
invalid capture index
While I now know it is because of the curly braces not being specified appropriately in the gsub pattern, I don't know how to fix it.
How should I form the gsub pattern so that I can replace the placeholder string with the email address value?
I've looked around on all the lua-oriented sites I can find but most of the documentation seems to revolve around unassociated situations.
As I've suggested in the comments above, when the e-mail is encoded as a URL parameter, the %40 used to encode the '@' character will be used as a capture index. Since the search pattern doesn't have any captures (let alone 40 of them), this will cause a problem.
There are two possible solutions: you can either decode the encoded string, or encode your replacement string to escape the '%' character in it. Depending on what you are going to do with the end result, you may need to do both.
the following routine (I picked up from here - not tested) can decode an encoded string:
function url_decode(str)
str = string.gsub (str, "+", " ")
str = string.gsub (str, "%%(%x%x)",
function(h) return string.char(tonumber(h,16)) end)
str = string.gsub (str, "\r\n", "\n")
return str
end
For escaping the % character in string str, you can use:
str:gsub("%%", "%%%%")
The '%' character is escaped as '%%', and it needs to be ascaped on both the search pattern and the replace pattern (hence the amount of % characters in the replace).