I don't understant when I need to use "local"

[IIYAMA]

I don't understant when I need to use "local"

Wiki:

A local variable only exists within the scope it is declared. The scope is the 'level' the variable is visible for the script, containing the value that was assigned to it.

You should use local variables anytime it is possible, when you don't need to access them globally. This saves you from having troubles with duplicate variable names. Plus, access to local variables is faster.

It is thus also good practice to declare as local any variables that are to exist in any scope within a script file, by declaring it using local outside any blocks. The main reason to make a variable global in a resource is when it must be accessed by more than one script file in the resource. Since all script files within a resource share the same global environment, it makes sense to use a global variable here.

The health variable only exists within the if-condition block, that is between the 'then' and the 'end'.  

They mean this?

function epic () 
  if 7 > 3 then--starts? 
  local P = 1 
  if P then 
  outputChatBox("this works") 
  end 
  end--ends? 
end 

I know what they mean, but I don't know when I need to use it:

Their samples:

local playermoney = getPlayerMoney ( source )

local health = getElementHealth(player)

Do I need local for math? or will it only make lagg.

number1 = 1

number2 = 2

number3 = number1 + number2

outputChatBox(number3)

Do I need local for tables?

number3 = {[3] = 1,[2] = 2,[1] = 3}

I hope you can explane to me when I do need to use local and when I don't need to use it.

THX

[IIYAMA]

Lol nobody?

[AhmadQTR]

Lol nobody?

Well i just know that 'local' defines something like

local playername = getPlayerName (source) -- gets the player name 
local root = getRootElement() --gets root element 
function output () 
outputChatBox ( playername.."Has Joined the server!", root, 255, 255, 100, true ) 
end 
addEventHandler ( "onPlayerJoin", root, output ) 

[myonlake]

local means it will only be shared by the function it is underneath. If I make a function and make a local in it, it means it will not be working outside the function. If I didn't make it local, as in, keep it global, it could be fetched by any other function.

[IIYAMA]

thank you,

just one more question.

  
local H = 1 -- set H to 1 
local G = 0 -- set G to 0 
  
  
function normal () 
  
 if H == 1 then -- check if H is 1  
  local G = 1 -- make local  
 end 
  
 if G == 1 then -- check if G is 1 
  outputChatBox ("G") -- will it output G? 
 end 
  
end 
  
normal() --trigger 
  

because they say at wiki:

local showHealth = true 
  
outputChatBox("This is your status:", player) 
if showHealth == true then 
    local health = getElementHealth(player) 
    outputChatBox("Health: "..tostring(health), player) 
end 

The health variable only exists within the if-condition block, that is between the 'then' and the 'end'.

[Anderl]

local means it will only be shared by the function it is underneath. If I make a function and make a local in it, it means it will not be working outside the function. If I didn't make it local, as in, keep it global, it could be fetched by any other function.

To be more accurate, a local variable is shared ONLY in the scope it was defined.

Example:

function myFunction( ... ) 
    --blabla my code 
    if ( ... ) then 
        local varArgs = { ... }; 
        outputChatBox( varArgs[1] == "I like cookies." and "..............................." or varArgs[2] == "I love them." and "No, you don't.", root, 255, 255, 255, false ); 
    end 
    if ( not varArgs ) then 
        outputChatBox( "varArgs not defined in this scope.", root, 255, 255, 255, false ); 
    end 
end 

Output:

............................... / No, you don't. 
varArgs not defined in this scope. 

[IIYAMA]

so:

function myFunction( ... ) 
    if ( ... ) then 
        local varArgs = { ... }; 
         -- it can be used here 
    end 
    if ( not varArgs ) then 
    -- it can't be used here. 
    end 
end 

right?

[Castillo]

Exactly.

[Anderl]

The statement with "not varArgs" condition is not needed, it was just to show you that it would not work outside of the scope ( in this case, out of the if statement ). So:

A local variable out of anything -> not shared with other files;

A local variable in a function -> not shared with the rest of the script, it's only shared in the function and ONLY if it's out of a statement or any function inside of that one.

A local variable in a statement/function inside function -> not shared with its "main function" neither with the rest of the script.

[IIYAMA]

Thank you all,

Your explanations were very clear.

[Anderl]

You're welcome

[myonlake]

@Anderl: COMPETITION (not really)

You're welcome