Conditional Switches

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Inhaltsverzeichnis 1 Conditional Switches 1.1 Problem definition 1.2 Solution 1.3 Solution example 1.4 Analysis

Conditional Switches

Problem definition

You have several switches and something is to be switched if e.g. first, second and third switches are on and the fourth and fifth off. In all other cases nothing is to happen.

Solution

We record the states of all switches in a table (Array). Each switch manages therein its state. After anyone operates a switch, you call an evaluation function, which can make arbitrary inquiries to the table.

Solution example

switch_pos = {{1,1},{2,3},{4,6},{5,7},{8,9}}
num_switches = table.getn(switch_pos)
bool_tab = {}
 
-- Object:
for i=1, num_switches do 
    bool_tab[i] = 0
    set_stone("st-switch", 2+i,2,{name="switch"..tostring(i), action="callback", target="change_state", _senderid=i })
end
 
set_stone("st-oneway-e", 5, 10, {name="one-way"})
 
-- Action:
function evaluate()
    local one-way=enigma.GetNamedObject("one-way")
    if bool_tab[1] == 1 and bool_tab[2] == 1 and bool_tab[3]==1 and bool_tab[4]==0 and bool_tab[5]==0 then
        SendMessage(one-way,"flip")
    end
end
 
function change_state(onoff, sender)
    local id = enigma.GetAttrib(sender, "_senderid")
    bool_tab[id] = 1 - bool_tab[id]
    evaluate() 
end

Analysis

First the necessary variables are defined.

• switch_pos is an array, which stores the positions of the switches.
  
• num_switches is the number of switches. It is computed directly from switch_pos.
  
• bool_tab is the table (array) that stores those the conditions of all switches.

Then the objects are set and initialized equal to bool_tab. The switches will provide senderid with an additional attribute. It is a unique, whole number, which is used as an index for bool_tab.

Every time, if a switch is now operated, the function change_state is called. It manages the status of the switches in bool_tab. It inverts it in each case. Afterwards it calls the function evaluate.

Evaluate now examines whether all conditions is fulfilled, and the target may be implemented. It places all inquiries to the bool_tab and evaluates it. In the example, if the 1st, 2nd and 3rd switches are on (bool_tab[id]==1) and the 4th and 5th are off (bool_tab[id]==0), then the direction of the Oneway is changed.

If now another switch is toggled - the condition is no longer fulfilled - the direction does not return to the original state. This only happens, if a player sets the correct state again.

If however you want the direction to changes again, as soon as the condition is no longer fulfilled, you must add into the evaluate function a second branch (else). That could look something like this:

function evaluate()
    local one-way=enigma.GetNamedObject("one-way")
    if bool_tab[1] == 1 and bool_tab[2] == 1 and bool_tab[3]==1 and bool_tab[4]==0 and bool_tab[5]==0 then
        SendMessage(one-way,"flip")
    else
        SendMessage(one-way,"direction", EAST)
    end
end

You cannot simply send a flip message again, since the direction would otherwise change with each switching.