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41. Re: Suggestion: Deprecate "Attempt to index a nil value" error; instead, return nil or create table (score: 539)

Author: Diego Nehab <diego@...>

Date: Fri, 6 Mar 2020 16:24:46 -0300

Ah, the thread has been broken a couple times. Apologies. I would have replied to it instead. Is this the message you mean?    http://lua-users.org/lists/lua-l/2020-03/msg00017.html Anyway, the point

42. Re: Suggestion: Deprecate "Attempt to index a nil value" error; instead, return nil or create table (score: 539)

Author: Luiz Henrique de Figueiredo <lhf@...>

Date: Wed, 4 Mar 2020 06:42:42 -0300

You can avoid special fields like that by using a separate table for private attributes: local Sparse = {} local Attr = setmetatable({}, {__mode = ?k?}) local function new(dimension) local sparse =

43. Re: [5.1.4] "attempt to index global 'data' (a nil value) (score: 461)

Author: "Xu, Gang L" <gang.l.xu@...>

Date: Sun, 24 Jul 2011 15:25:03 -0400

D[ 'data' is nil because io.open returns nil on failure. I would suggest the following first line: data = assert(io.open([[C:\places.txt]],"r")) Note two things: 1) The call to assert to raise any er

44. RE: [5.1.4] "attempt to index global 'data' (a nil value) (score: 454)

Author: Dave Collins <Dave.Collins@...>

Date: Tue, 26 Jul 2011 15:59:41 -0400

Sorry, I see the other responses now. This got trapped as spam so it stuck out as a singleton post. (Trying to contribute back the the community that's been so much help) Dave Collins Hello Using a

45. RE: [5.1.4] "attempt to index global 'data' (a nil value) (score: 454)

Author: Dave Collins <Dave.Collins@...>

Date: Tue, 26 Jul 2011 15:55:55 -0400

I'm pretty new but it looks like no one's responded. It seems to me what you want to do is this: local data = assert(io.open("C:\places.txt","r")) if (data) then for line in data:lines() do ... else

46. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 454)

Author: "Patrick Mc(avery" <spell_gooder_now@...>

Date: Fri, 18 Feb 2011 06:49:14 -0500

I'm trying to create a text file, and google for samples on how to do this, but regardless of using a global or local variable to hold the file descriptor, I get the following error: "attempt to inde

47. [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 454)

Author: Gilles Ganault <gilles.ganault@...>

Date: Fri, 18 Feb 2011 12:53:42 +0100

Hello I'm trying to create a text file, and google for samples on how to do this, but regardless of using a global or local variable to hold the file descriptor, I get the following error: "attempt t

48. Re: [5.1.4] "attempt to index global 'data' (a nil value) (score: 448)

Author: Peter Cawley <lua@...>

Date: Sun, 24 Jul 2011 14:03:32 +0100

'data' is nil because io.open returns nil on failure. I would suggest the following first line: data = assert(io.open([[C:\places.txt]],"r")) Note two things: 1) The call to assert to raise any error

49. Re: ERROR: lua: simpleApp1.lua:1: attempt to index global 'fltk' (a nil value) (score: 445)

Author: Patrick Rapin <toupie300@...>

Date: Wed, 22 Dec 2010 20:39:14 +0100

Maybe that the script you are quoting has been written for murgaLua [1], a Lua distribution with a built-in FLTK binding. I have tried that code with the Windows murgaLua 0.6.8 executable and it work

50. [5.1.4] "attempt to index global 'data' (a nil value) (score: 441)

Author: Gilles Ganault <gilles.ganault@...>

Date: Sun, 24 Jul 2011 14:56:24 +0200

Hello Using a Lua script on XP, I need to open an HTML file and extract hyperlinks... == data = io.open("C:\places.txt","r") for line in data:lines() do for token in string.gmatch(line, '<a href="(/p

51. Re: ERROR: lua: simpleApp1.lua:1: attempt to index global 'fltk' (a nil value) (score: 441)

Author: HyperHacker <hyperhacker@...>

Date: Tue, 21 Dec 2010 18:50:18 -0700

Well you haven't included the fltk module. The '#' is a bit worrisome too; are you running this as root? -- Sent from my toaster.

52. ERROR: lua: simpleApp1.lua:1: attempt to index global 'fltk' (a nil value) (score: 441)

Author: Shamun toha md <shamun.toha@...>

Date: Wed, 22 Dec 2010 01:59:32 +0100

stack traceback: simpleApp1.lua:1: in main chunk [C]: ? #  $ cat simpleApp1.lua    do local object = fltk:Fl_Double_Window(166, 165, "My App");     window = object;     fltk:Fl_Return_Button(5, 130,

53. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 440)

Author: Andrew Wilson <agrwagrw@...>

Date: Fri, 18 Feb 2011 09:03:03 -0500

-- slight typo don't forget table parameter in index.. do local mt = getmetatable(_G) or {} mt.__index = function(t,k) error("Global "..k.." does not exist", 2) end setmetatable(_G, mt) end n1="strin

54. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 436)

Author: Axel Kittenberger <axkibe@...>

Date: Fri, 18 Feb 2011 15:19:11 +0100

Chap. 14.2 in the book does, but it doesn't mention etc/strict.lua, didn't notice a forward link in the errors chap. Would be a good idea for that cookbook :)

55. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 436)

Author: Gilles Ganault <gilles.ganault@...>

Date: Fri, 18 Feb 2011 15:09:24 +0100

Speaking of which, is there a good article/tutorial/chapter for newbies on debugging Lua scripts, besides Chapter 8 in the PiL? www.lua.org/pil/index.html#8 The online PiL is from 2004, and doesn't m

56. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 436)

Author: Axel Kittenberger <axkibe@...>

Date: Fri, 18 Feb 2011 14:53:25 +0100

Best is to add a metatable to globals _G that errors on index. Put this on top of your program. do local mt = getmetatable(_G) or {} mt.__index = function(k) error("Global "..k.." does not exist", 2

57. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 432)

Author: Michal Kottman <k0mpjut0r@...>

Date: Fri, 18 Feb 2011 21:31:07 +0100

__index and __newindex always receive the table as the first argument (see http://www.lua.org/manual/5.1/manual.html#2.8 and http://www.lua.org/pil/13.4.1.html ). So the correct signature should be:

58. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 432)

Author: Steve Litt <slitt@...>

Date: Fri, 18 Feb 2011 14:32:33 -0500

Axel, This is wonderful. It's like "use strict" for Lua. However, I had a problem with your code because k was always a table, regardless of the global I read or wrote (I also added a __newindex() to

59. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 432)

Author: Luiz Henrique de Figueiredo <lhf@...>

Date: Fri, 18 Feb 2011 11:59:32 -0200

See also etc/strict.lua which does this and more.

60. Re: [5.1.4/newbie] "attempt to index ... 'file' (a nil value)"? (score: 432)

Author: Gilles Ganault <gilles.ganault@...>

Date: Fri, 18 Feb 2011 14:56:57 +0100

Thanks Axel. I'll give it a try.