Lua/Tables

Lua modules based on the Scribunto/Lua extension are stored in resource pages using the Module: namespace. Each module uses a table to hold functions and variables, and that containing table is returned at the end of the module code. Tables are associative arrays or collections of data with key / value pairs that may be used to hold, organize and access data. This lesson will show you how to use tables in your scripts.

Prerequisites
This lesson assumes you have already completed the Functions lesson.

Create a Lua Script with Tables
To create a Lua script with tables: ""
 * 1) Navigate to Module:Sandbox.
 * 2) Clear all existing code.
 * It's a sandbox. Everyone is free to play in the sandbox.  But if you find another user is actively editing the sandbox at the same time, you may also use Module:Sandbox/Username, where Username is your Wikiversity username.
 * 1) Add the following code and save the page:

Test Your Lua Script
To test your Lua script:
 * 1) Navigate to either the Module_talk:Sandbox page, the Sandbox page, or your own user or sandbox page.
 * 2) Add the following code and save the page:

The result should be similar to:
 * sequence
 * table[1] is 10
 * table[2] is 20
 * table[3] is 30


 * dictionary
 * table['es'] is Spanish
 * table['ja'] is Japanese
 * table['fr'] is French
 * table['ru'] is Russian
 * table['de'] is German
 * table['ko'] is Korean
 * table['en'] is English
 * table['zh'] is Chinese
 * table['it'] is Italian

Understand Your Lua Script
To understand your Lua script  function:
 * 1)   declares a local function named   that accepts a single parameter , which is the table to be converted to a string.
 * 2)   and the following code defines the variables ,  , and  .  All are.
 * 3)   assigns an empty string literal value to the variable.
 * 4)   creates a loop code block that will vary the value of the variables   and   for each key/value data pair in the table.
 * 5)   tests to see if the key can be converted to a number.  If it can, the key is displayed as a number (without quotes).  If it can't be converted, the key is displayed as a literal string (with quotes).
 * 6)   or   adds the current key and value to the result.
 * 7) * The  notation is a common way to reference individual table keys to access their associated values.
 * 8) * To display quotes inside a string, you must either switch between quote identifiers ("/'), or use the \ character to 'escape' the quote, which forces it to be part of the string rather than terminate the string.
 * 9)   ends the loop.
 * 10)   returns the current value of   as the result of the function.
 * 11)   ends the function.

To understand your Lua script  function:
 * 1)   declares a function named sequence.
 * 2)   defines a local table variable named , which is initialized with three values.
 * When table values are specified without matching keys, Lua automatically adds numeric keys for the values as a sequence from 1 to N, the number of values added. This allows Lua tables to be used similar to how arrays are used in other programming languages.  For example, the second value in the table could be referenced as , and the table values could be processed with a for loop.
 * 1)   defines the variable   and initializes it to.
 * 2)   assigns a literal string value to the variable  . The semi colon is an operator that separates each new statement and the /n means new line.
 * 3)   calls the   function, passing the table   as the parameter and concatenates the returned value to the variable.
 * 4)   returns the current value of   as the result of the function.
 * 5)   ends the function.

To understand your Lua script  function: It is important to note that the for loop to process table pairs will process all values in the table, but tables with specified key values may not be processed in the order they were created.
 * 1)   declares a function named dictionary.
 * 2)   and the following code defines a local table variable named , which is initialized with 9 key/value pairs.
 * 3) * When table values are specified with matching keys, Lua uses the specified keys instead of numeric key values.
 * 4) * Lua tables with specified key values cannot be used as arrays using  notation.
 * 5) * Lua tables with specified key values can be used as associative arrays using  notation, such as  .  Quotes around string literal keys are required with this notation format.
 * 6) * Lua tables with specified key values can also be used as associative arrays using  notation, such as  .  Quotes around string literal keys are not required with this notation format.
 * 7)   defines the variable   and initializes it to.
 * 8)   assigns a literal string value to the variable.
 * 9)   calls the   function, passing the table   as the parameter and concatenates the returned value to the variable.
 * 10)   returns the current value of   as the result of the function.
 * 11)   ends the function.

Conclusion
Congratulations! You've now created, tested, and understood a Lua script with tables. Continue on to the ../Errors/ lesson.