Trying to get the values of sliders from a module

Question

I generated n number of Sliders using the idea from Manipulate with a variable number of sliders

But I need the updated values of these sliders to use to evaluate a function . I tried couple of things but I could not figure is out. I can get the values but even if I have 4 values , the dimension of the data is 1.How can I get these values?

  ClearAll@Preplot;
  SetAttributes[Preplot, HoldFirst]; 
  Preplot[u_, vars_, poi_] := Module[{v1, v2, posv1, posv2, vars1} ,
  v1 = poi[[1]];  (*Get the first variable for the plane of interest *)
  v2 = poi[[2]]; (*Get the second variable for the plane of interest *)
  posv1 = Position[vars, v1][[1]]; (* Position of v1 in vars list  *)
  posv2 = Position[vars, v2][[1]]; (* Position of v2 in vars list  *)
  lv1 = vars[[posv1[[1]], 2, 1]];    (*Lower limit of v1*)
  lv2 = vars[[posv2[[1]], 2, 1]]; (*Lower limit of v2*)
  rv1 = vars[[posv1[[1]], 2, 2]]; (*Upper limit of v1*)
  rv2 = vars[[posv2[[1]], 2, 2]]; (*Uppler limit of v2*)
  (*Print[{lv1,rv1,lv2,rv2}];*)
  (* Create a new list of the other dimensions vars1*)
  vars1 = Delete[vars, {{posv1[[1]]}, {posv2[[1]]}}]; 
  countersvar = Dimensions[vars1][[1]]; (*Size of it*)
  (* Lower and upper limits of n-2 variables *)

  limsL = ConstantArray[0, countersvar]; 
  limsR = ConstantArray[0, countersvar];
  lims = ConstantArray[0, countersvar];
  steplims = ConstantArray[0, countersvar];
  midpoints = ConstantArray[0, countersvar];
  transferd = ConstantArray[0, countersvar];
  Do[
  lims[[i]] = vars1[[i, 1]]; (*The variable *)

  limsL[[i]] = vars1[[i, 2, 1]]; (*Lower Limit*)

  limsR[[i]] = vars1[[i, 2, 2]]; (*Upper Limit*)

  steplims[[i]] = (-vars1[[i, 2, 1]] + vars1[[i, 2, 2]])/25; 

  midpoints[[i]] = 
  vars1[[i, 2, 1]] + (-vars1[[i, 2, 1]] + vars1[[i, 2, 2]])/
  2; (*Mid point for the sliders*)
 , {i, countersvar}];
 (*Dynamically create n-2 sliders*)
  data = midpoints;
  controls = 
  DynamicModule[{n = Length[midpoints]}, 
  Column[{Dynamic[
   Grid[Table[
     With[{i = i}, {lims[[i]], 
       Slider[Dynamic[data[[i]]], {limsL[[i]], limsR[[i]], 
         steplims[[i]]}], Dynamic[data[[i]]]}], {i, n}]]],
  Dynamic[data[[i]]];,
  (*I need to do the following because I can't use poi[[
  1]] as an argument in the plot3d*)
    (* 
  and for some reason I need to create new u function in every \
  change*)
  u1 = u /. poi[[1]] -> v3;
  u2 = u1 /. poi[[2]] -> v4;
  (*Here is my problem I need to do evaluate the u function with \
  the dynamic data which is changing as the user using sliders. 
  First I know that  Dynamic@data[[1]] is a number. 
  So I need each sliders numeric value so I can evaluate the \
  function wrt to corresponding slider value dynamically. *)

  u2 = u2 /. lims[[1]] -> Dynamic@data[[1]];
  u2 = u2 /. lims[[2]] -> Dynamic@data[[2]];
  u2 = u2 /. lims[[3]] -> Dynamic@data[[3]];
  u2 = u2 /. lims[[4]] -> Dynamic@data[[4]];
  Print[
   SetAccuracy[u2, 
    30]];  (*As you can see that the number are not evaluated *)
    \
  (*I need to evaluate u2 in a doloop of table because number of \
  variables can change *)
  (*Do[
  u2=u2/.lims[[i]]\[Rule]Dynamic@data[[i]];
  ,{i,n}];*)


  (* my goal is to able dynamically plot 2D slices of n \
     dimensional function. 
  And user will change dynamically how this 2D evaluated as well \
    as plane of interest by rerunning the code. *)

  Plot3D[u2, {v3, lv1, rv1}, {v4, lv2, rv2}, 
   PerformanceGoal -> "Quality", Mesh -> None, 
   ColorFunction -> Function[{x, y, z}, Hue[z]], 
   ImageSize -> Medium]

  }, Center]];

  Return[controls];
       ];

   (* Variables  and their limits    *)

  vars = {{x, {1, 2}}, {z, {3, 4}}, {y, {5, 6}}, {l, {7, 8}}, {w, {9, 
 10}}, {o, {11, 12}}};
  poi = {x, w};  (*Plane of interest*)
  u = Cos [x z] + Sin [Pi y l] + w^2/o;   (*Function*)
  Preplotvar = Preplot[u, vars, poi]

Answer 1

There may be a confusion in what Dynamic really is and how to use it. Follow those links please:

1. Programming with Dynamic
2. Why won't this work? Dynamic in a Select
3. IntroductionToDynamic
4. AdvancedDynamicFunctionality
5. Synchronizing code in Dynamics with other procedures

---

The very last edit I will make here.

From your recent questions and updates I think you have to work more ("hands on") with sources I've provided above.

Doing things like u2 = u2 /. lims[[1]] -> Dynamic@data[[1]]; and expecting to perform calculations on u2 indicates that you don't know what Dynamic is for even though you've already been told about relevant tutorials/sources.

Not to mention Dynamic[ data[[i]] ]; in the column.

Nevertheless, this is a minimal example of code which is supposed to do what you want:

DynamicModule[{x = 0, y = {1, 0}},
 Column[{
   Slider@Dynamic[x],
   Dynamic[
    y = {1, x}; (*complicated stuff you want to do with x whenever Slider    changes it*)
    ListLinePlot[y, PlotRange -> 1] (*and a result you want the user to see*)
    ]
   }]
 ]

For heavy/time consuming procedures you may want to use SynchronousUpdating -> False - take a look at AdvancedDynamicFunctionality. You can also use DynamicWrapper for a more idiomatic approach to "background calculations". If you want to learn more follow the 5th link and linked sources there.

---

Old stuff, not so relevant since an original code was deleted.

Now, this should be more flexible approach, pass a symbol to Preplot, treat Preplot as a controller. I think it is also a more idiomatic approach.

ClearAll@Preplot;
SetAttributes[Preplot, HoldFirst];

Preplot[data_, lims_, initialData_, limsL_, limsR_, limsteps_] := 
  DynamicModule[{n = Length[initialData]},
   data = initialData;
   Grid[Table[With[{i = i},
      {
       lims[[i]],
       Slider[
         Dynamic[data[[i]]], {limsL[[i]], limsR[[i]], limsteps[[i]]}
       ], 
       Dynamic[data[[i]]]
       }
      ],
     {i, n}
     ]]
   
   ];

lims = {x, z, y, p};
midpoints = {0.5, 3, 4.5, 7};
limsL = {0, 2, 3, 4};
limsR = {1, 4, 6, 10};
limsteps = (limsL - limsR)/25;

Preplot[data, lims, midpoints, limsL, limsR, limsteps]

Dynamic@ First @ data (*First or whatever you want to do*)

Answer 2

Here is the solution. It was too obvious maybe, sorry for taking so many time in here.

    ClearAll@Preplot;
    SetAttributes[Preplot, HoldFirst]; 
    Preplot[u_, vars_, poi_] := Module[{v1, v2, posv1, posv2, vars1} ,
    v1 = poi[[1]];  

    v2 = poi[[2]];   
    posv1 = Position[vars, v1][[1]]; (* Position of v1 in vars list  *)

    posv2 = Position[vars, v2][[1]]; (* Position of v2 in vars list  *)

    lv1 = vars[[posv1[[1]], 2, 1]];    (*Lower limit of v1*)

    lv2 = vars[[posv2[[1]], 2, 1]]; (*Lower limit of v2*)

    rv1 = vars[[posv1[[1]], 2, 2]]; (*Upper limit of v1*)

    rv2 = vars[[posv2[[1]], 2,  2]]; (*Upper limit of v2*)
    (*Print[{lv1,rv1,lv2,rv2}];*)
   (* 
   Create a new list of the other dimensions vars1*)
   vars1 = Delete[vars, {{posv1[[1]]}, {posv2[[1]]}}]; 
   countersvar = Dimensions[vars1][[1]]; (*Size of it*)
   (* 
   Lower and upper limits of n-2 variables *)

   limsL = ConstantArray[0, countersvar]; 
   limsR = ConstantArray[0, countersvar];
   lims = ConstantArray[0, countersvar];
   steplims = ConstantArray[0, countersvar];
   midpoints = ConstantArray[0, countersvar];
   transferd = ConstantArray[0, countersvar];
    Do[
    lims[[i]] = vars1[[i, 1]]; (*The variable *)

    limsL[[i]] = vars1[[i, 2, 1]]; (*Lower Limit*)

   limsR[[i]] = vars1[[i, 2, 2]]; (*Upper Limit*)

    steplims[[i]] = (-vars1[[i, 2, 1]] + vars1[[i, 2, 2]])/
    25; (*Step size for the slider*)

    midpoints[[i]] = 
    vars1[[i, 2, 1]] + (-vars1[[i, 2, 1]] + vars1[[i, 2, 2]])/
    2; (*Mid point for the sliders*)
   , {i, countersvar}];
   (*Dynamically create n-2 sliders*)
   data = midpoints;
   controls = 
   DynamicModule[{n = Length[midpoints]}, 
   Column[{Grid[
   Table[With[{i = i}, {lims[[i]], 
      Slider[Dynamic[data[[i]]], {limsL[[i]], limsR[[i]], 
        steplims[[i]]}], Dynamic[data[[i]]]}], {i, n}]],

   Dynamic[u1 = u /. poi[[1]] -> v3;
    u2 = u1 /. poi[[2]] -> v4;

     Do[
     u2 = u2 /. lims[[i]] -> data[[i]];
     , {i, n}];


    Plot3D[Evaluate[u2], {v3, lv1, rv1}, {v4, lv2, rv2}, 
    PerformanceGoal -> "Quality", Mesh -> None, 
    ColorFunction -> Function[{x, y, z}, Hue[z]], 
    ImageSize -> 200]]

     }, Center]];

    Return[controls];
    ];
  (* Variables  and their limits    *)
  vars = {{x, {1, 2}}, {z, {3, 4}}, {y, {5, 6}}, {l, {7, 8}}, {w, {9, 
  10}}, {o, {11, 12}}};
  poi = {x, w};  (*Plane of interest*)

  u=Cos [x z] + Sin [Pi y l] + w^2/o;   (*Function*)
  Preplotvar =  Preplot[u, vars, poi]