dynamic - A good way to manage code in a complicated CDF?

When doing complicated programming in a Mma notebook I define several functions that I use in my higher level funtions, and I use a "Subsection" cell for each definition. For example I might write:

Cell["foo[x,y]", "Subsection"]
foo[x_,y_]:=(* complicated code *)


Cell["foo[x,y,z]", "Subsection"]
foo[x_,y_,z_]:=(* complicated code *)

Cell["goo[x,y]", "Subsection"]
goo[x_,y_]:=(* complicated code *)

Cell["UserIterface[x,y,z]", "Subsection"]
UserInterface[x_,y_,z_]:=DynamicModule[{a,b,c},
  a=foo[x,y];

  b=foo[x,y,z];
  c=goo[x,y];
  (* and so on  *)
]

By using "Subsection" cells, I can close Subsections of code when I don't need to see them. However, I want to make my program a CDF that the CDF-Player can use. As far as I know, I have to use the following approach instead.

DynamicModule[{a,b,c},
a=foo[x,y];
b=foo[x,y,z];
c=goo[x,y];

(* and so on  *),

Initialization:>{
foo[x_,y_]:=(* complicated code *);
foo[x_,y_,z_]:=(* complicated code *);
goo[x_,y_]:=(* complicated code *)}
]

This becomes unwieldly because I can't minimize the code that I don't need to see at any moment. Is there a better way to make a complicated CDF?

Answer

It is not necessary to put all your functions into the DynamicModule/Manipulate when deploying to CDF: you can use SaveDefinitions -> True to collect function definitions from other cells or even from packages, though only for non-free CDFs, that can be opened only with Mathematica or Player Pro. If deploying for the web or for the free CDF Player, the situation is not that simple. For security reasons, SaveDefinitions won't grab all functions defined in other cells or packages, especially since some functionality is disallowed in the free CDF version.

Also note, that CDF's don't evaluate cells in the order they appear, i.e. initialization cels are not evaluated before everything else! Accordingly, all content for a CDF (if it is outside of the Manipulate/DynamicModule) should be in the same dynamic cell, where the actual dynamic CDF content resides, to make sure they got evaluated together.

See full discussion of these issues here: Understanding CDF, especially point 2: Save definitions.