Lua/Conditions

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. Conditions are code structures used to make choices and control the flow of scripts. This lesson will show you how to use conditions in your scripts.

Prerequisites

This lesson assumes you have already completed the Expressions lesson.

Create a Lua Script with Conditions

To create a Lua script with conditions:

1. In Module:Sandbox, click Edit source.
2. Replace existing code pasting the following code without clicking Publish changes.

local p = {}
function p.conditions() -- Greetings according to the hour
    local hour = tonumber(os.date('%H')) -- Get current Hour
    if hour < 12 then
        return 'Good morning!'
    elseif hour < 18 then
        return 'Good afternoon!'
    else
        return 'Good evening!'
    end
end
return p

Debug Your Lua Script

To test your Lua script:

1. Scroll down until Debug console at the end of the page.
2. Paste the following call and validate by Enter: ↲

print(p.conditions())

The result should be either:

Good morning!

or

Good afternoon!

or

Good evening!

depending on the UTC time of day.

Click Cancel. "Leave site?" Click Leave. Close Module:Sandbox.

Understand Your Lua Script

To understand your Lua script:

1. local and the following code defines the variable hour.
2. os.date('%H') returns the current server time formatted in hours (%H) from 0 to 23 as a string. Server time is typically set to UTC rather than local time.
3. tonumber() converts the string to a number.
4. hour = stores the numeric value of the server time in the variable hour.
5. if hour < 12 then begins a conditional code block and checks hour to see if it is less than 12. If it is, the following statement(s) are executed. If not, the following statements are skipped.
6. return 'Good morning!' sets the value of result.
7. elseif hour < 18 then checks hour to see if it is less than 18. If it is, the following statements are executed. If not, the following statements are skipped.
   • Conditions are mutually exclusive. If the first condition was true (if), the second condition (elseif) is not evaluated.
   • elseif is optional in a conditional code block and may be repeated.
8. else indicates that if none of the previous conditions were true, the following statements are executed. If one of the previous statements was true, the following statements are skipped.

   else is optional in a conditional code block.

9. end ends the conditional code block.

Conclusion

Congratulations! You've now created, tested, and understood a Lua script with conditions. Continue on to the Loops lesson.

See Also

• Wikipedia: Conditional (computer programming)

References

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Lua

Loops →