6 replies to this topic

[Mackan90096]

Hi there!

I'm working on my ccSQL project.
I get the error: ccsql:50: bad argument: string expected, got nil

Line 50 is in this case line 16.
Code for the function:
Stupid forum, breaking my indentation

Spoiler

function select(what,dbname,equals)
dbName = tostring(dbname)
c1 = tostring(what)
c2 = tostring(equals)

if fs.exists(dbName) then
f = fs.open(dbName, "r")
line = f.readAll()
if c1 == "*" then
print(line)
f.close()
else
if string.find(line, c1) then
pos = string.find(line, c1)
lenght = f.readLine(1)
leng = string.len(lenght)
found = true
v1 = string.sub(line, leng+1, string.len(c1)) 
v2 = string.sub(line, leng+3,string.len(c2))
print("Found!")
print("What: "..v1.." Value: "..v2)
print(line)
f.close()
else
print("No matches")
f.close()
end
end
else
print("No such database")
end
end

And this is what executes it:

Spoiler

os.loadAPI("ccsql")

ccsql.select("Name", "Test", "Hai", "Nop")

[Wojbie]

in line 8 - line = f.readAll() - that reads whole file - leaves marker on eof

line 15 - lenght = f.readLine(1) - attempts to read next line after marker - but there is nothing cause readAll read it all - gets eof - returns nil
line 16 - leng = string.len(lenght) - tries to get length on nil - error.


Also i don't think that readLine accepts any arguments?If it does its not documented in wiki. It just reads next line after marker. You are trying to reread line number 1 here?

[Mackan90096]

wojbie, on 15 October 2013 - 04:06 AM, said:

You are trying to reread line number 1 here?

Yes

[Wojbie]

2 ways to sole it Adwanced and Easy

Easy - simply close and reopen file - that will rester market and readline would restart from beginning of file
So to get to 5 line simply readline 5 times and last one gives you 5th line.

Advanced - you readAll or readLine whole file store it in table or somewhere and work on table instead of file.

[Engineer]

This is a proper way of reading a file line by line:

local lines = {}

local file = fs.open( "file", "r" )

for line in file.readLine do
	table.insert( lines, line )
end

file.close()

This way you can easily find your lines; lines[ 1 ] is the first line. Now, you should keep this table for later one, so you dont have to open unneccesarily files.

[MKlegoman357]

Tips:

• Localize variables (you should know what it is and why you should do it).
  
• Next time when pasting your code, indent it after you paste it.
  
• You can use # to get length of strings and tables:
  

  local text = "Hi"
  local info = {"Yes", 2}
  
  print(#text)
  -->> 2
  
  print(#info)
  -->> 2
  
  print(#info[1])
  -->> 3
  

[Mackan90096]

wojbie, on 15 October 2013 - 06:10 AM, said:

2 ways to sole it Adwanced and Easy

Easy - simply close and reopen file - that will rester market and readline would restart from beginning of file
So to get to 5 line simply readline 5 times and last one gives you 5th line.

Advanced - you readAll or readLine whole file store it in table or somewhere and work on table instead of file.

I'll do it the Easy way. Thanks!