Scripting, Tutorials

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This tutorial teach you an easy way to manage your URL parameters in your application by using LUA metatables.

Warning: This tutorial is only viable for games using the Lua script, it doesn’t work for games exported in native code, because it uses LUA elements

Introduction

Metatables in LUA are a kind of hashtable. You can associate a key and a value. Here, the key can be anything (number, string, object…)
The URL post parameters is a list of “parameter_key=parameter_value”, separated by “&”.
We will use the parameter_keys as key of a metatable, and parameter_values as value.

Steps

1. In your game, where you want to create an url, declare the metatable like that:

local params = {}

2. Now, add all the parameters you want for your URL by adding each key and value of the parameter in the metatable, using this syntax:

params["page"]=""..this.nCurrentPage ( )
params["category"]=this.sCurrentCategory ( )

3. Create a function buildPost ( params ), taking in argument your metatable containing the URL parameters.
4. Start by declaring the result variable:

local sRes = ""

5. We will now create a loop for the metatable. For this kind of table, you mustn’t use the “for i” loop, but the “for each” one.
The syntax of this loop is:

for vKey in params
do
    local vValue = params[vKey]
 
end

6. Concat the key and the value, by adding a “=” between them. Do not forget to encode the value. Then add the param to the sRes variable.

local sParam = vKey.."="..string.encoreURL ( vValue )
sRes = sRes..sParam.."&"

7. At the bottom of the function, do not forget to remove the last “&”, and return the final string:

sRes = string.getSubString ( sRes, 0, string.getLength ( sRes ) - 1 )
return sRes

The whole function should now looks like that:

--------------------------------------------------------------------------------
function Facebook.buildPost ( params )
--------------------------------------------------------------------------------
 
    local sRes = ""
    for vKey in params
    do
        local vValue = params[vKey]
        local sParam = vKey.."="..string.encoreURL ( vValue )
 
        sRes = sRes..sParam.."&"
    end
 
    sRes = string.getSubString ( sRes, 0, string.getLength ( sRes ) - 1 )
    return sRes
 
--------------------------------------------------------------------------------
end
--------------------------------------------------------------------------------

8. Get back to the place where you have declared the metatable, and add this line:
local sUrl = this.sTheServerUrl ( )..”/search?”..this.buildPost ( params )

You can now use the url

Conclusion

By using this way, you can now easily build URLs in your game, just by creating a metatable, adding the post parameters in it and calling your buildPost function.