How to read text file and add lines to an array?

Getting Started Newbie Questions
#1

Hello,

I have a file which is full of questions and answers. The way it is formatted is a question line and then the next 4 lines are possible answers. The correct answer has an * in the text. How can i take this text file that I downloaded to the device and loop through the lines adding them to the array?

I want them in an array like this format below:

local myArray = {{“question”,“answer 1”,“answer2”,“answer3”,“answer4”}, next line, etc. }

The text file will be like this:

Question
Answer1

Answer2

Answer3

Answer4

Question
Answer1

Answer2

Answer3

Answer4

etc.

Thanks for your help!

Warren

#2

Hi Warren,

Please see the following guide about reading and writing files, in particular the “Reading Lines” sub-section.

http://docs.coronalabs.com/guide/data/readWriteFiles/index.html

Using that, you can process each line and add its contents to a table. If necessary, you can also “sub-process” each line by doing string matching on it, to determine which is the correct answer as it loops through the text file.

Take care,

Brent

#3

Thanks, that is exactly what I need. I can add another array column to hold which one is the answer.

I do need to learn more about arrays now. I need to find the same sort or page about creating arrays. What I need to know is how to first create an empty array and then add to an array. Any chance you have something for this?

I just saw the page in the docs for inserting into a table but that showed for inserting a single value. Can you show me in code how to insert, well, really just add to the end of an array a set like {“a”,“b”,“c”,“d”} into an array?

Thanks!

Warren

#4

Hi Warren,

Creating an empty array (table) is very standard, and you’ve probably done it before:

[lua]

local myArray = {}

[/lua]

Then, to add to it, you can simply use the “# +1” method:

[lua]

myArray[#myArray+1] = “newValue”

[/lua]

This will just add a new value at the next spot in the array, by counting the current number of items and adding another one.

Effectively, what’s happening is:

1st iteration: table is empty (0 elements). 0+1=1. Lua adds the new element at position 1.

2nd iteration: table has 1 element. 1+1=2. Lua adds the new element at position 2.

etc., etc…

Of course, this is only for an indexed array. If you’re inserting “dictionary” items (key-value pairs) then the counting system won’t work like this. But I think you’re using the indexed method, so don’t worry about it right now.

Brent

#5

Hi Warren,

Please see the following guide about reading and writing files, in particular the “Reading Lines” sub-section.

http://docs.coronalabs.com/guide/data/readWriteFiles/index.html

Using that, you can process each line and add its contents to a table. If necessary, you can also “sub-process” each line by doing string matching on it, to determine which is the correct answer as it loops through the text file.

Take care,

Brent

#6

Thanks, that is exactly what I need. I can add another array column to hold which one is the answer.

I do need to learn more about arrays now. I need to find the same sort or page about creating arrays. What I need to know is how to first create an empty array and then add to an array. Any chance you have something for this?

I just saw the page in the docs for inserting into a table but that showed for inserting a single value. Can you show me in code how to insert, well, really just add to the end of an array a set like {“a”,“b”,“c”,“d”} into an array?

Thanks!

Warren

#7

Hi Warren,

Creating an empty array (table) is very standard, and you’ve probably done it before:

[lua]

local myArray = {}

[/lua]

Then, to add to it, you can simply use the “# +1” method:

[lua]

myArray[#myArray+1] = “newValue”

[/lua]

This will just add a new value at the next spot in the array, by counting the current number of items and adding another one.

Effectively, what’s happening is:

1st iteration: table is empty (0 elements). 0+1=1. Lua adds the new element at position 1.

2nd iteration: table has 1 element. 1+1=2. Lua adds the new element at position 2.

etc., etc…

Of course, this is only for an indexed array. If you’re inserting “dictionary” items (key-value pairs) then the counting system won’t work like this. But I think you’re using the indexed method, so don’t worry about it right now.

Brent