Lua accessing values inside a 2D array

Question

It seems like this should be a simple thing. I have converted the following json structure to a lua table but I am having trouble trying to access the values inside of the array. I have looked through many questions and the internet in general and none of the examples I have tried work.

Here is the json that was converted to a lua table using cjson.decode

[{
    "user": "user_1",
    "password": "something",
    "id": "35",
    "message": "message 1"
},
{
    "user": "user_2",
    "password": "something",
    "id": "5c",
    "message": "message 2"
},
{
    "user": "user_3",
    "password": "something",
    "id": "7e",
    "message": "message 3"
},
{
    "user": "user_3",
    "password": "something",
    "id": "6f",
    "message": "message 4"
}]

I then try to access the variable like this:

ngx.say(users[0]["user"]);

However that does not work. I want to iterate the array and get out the user, password, id, and message at each index of the array but first I wanted to just see how to access the value of user at index 0 .. which should be user_1. I know this is a n00b question but any help would be greatly appreciated.

Piglet · Accepted Answer · 2017-11-10 21:32:55Z

2

Lua tables start at index 1 by default.

answered Nov 10, 2017 at 21:32

Piglet

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7 Comments

Joel Parker Over a year ago

yeah, thought of that and tried ngx.say(users[1]["user"]); but still no joy

Piglet Over a year ago

@JoelParker it would help if you'd provide an error message instead of just saying it does not work ;)

Joel Parker Over a year ago

this is for the lua module in nginx and it just crashes, no error given

Piglet Over a year ago

@JoelParker users[1]["user"] should work given that your json was loaded and decoded correctly. Add more code to your question.

luther Over a year ago

In that case, users is an empty table, so it won't work. (users[1] is nil.)

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