in Xcode this is called "Code Sense". And these icons also exist in Xcode 3.
Red: macros
- # = macro (think
#define)
Brown: Core Data / namespace
- C = modeled class
- M = modeled method
-
P = modeled property
-
N = C++ namespace
Orange: aliased types
- C̲ = Objective-C category
- E = enum
- T = typedef
Green: variables
- B = binding
- ƒ = function
- F = field
- K = constant
- L = local variable
- O = IBOutlet
- V = variable (can be ivar, global var, local var, etc.)
- x = parameter (think f(x))
Blue: methods
- A = IBAction
- M = method
- P = property
Purple: aggregate types
- C = class (Objective-C or C++)
- ₠ = class extension
- Pr = Objective-C protocol
- S = struct
- U = union
You should be able to look up the meanings from the filenames from/Developer/Library/PrivateFrameworks/DVTFoundation.framework/Resources/Xcode.SourceCodeSymbolKind.*.Icon.tiff. Note that, not all icons are used in Code Sense, as these are shared by all Xcode components.