Whitespace

• Tabs, not spaces.
• End files with a newline.

Documentation

• All method declarations should be documented.
• Comments should be hard-wrapped at 80 characters.
• Comments should be Tomdoc-style.
• Use #pragma marks to categorize methods and protocol implementations.

Properties and Instance Variables

• Never declare an ivar unless you need to change its type from its declared property.
• Prefer exposing an immutable type for a property if it being mutable is an implementation detail. This is a valid reason to declare an ivar for a property.
• Don't access an ivar unless you're in -init or -dealloc.
• Use dot-syntax for "simple" getters and setters, including class methods (like NSFileManager.defaultManager).
• Always declare memory-management semantics even on readonly properties.
• Declare properties readonly if they are only set once in -init.
• Don't use @synthesize unless the compiler requires it.
• Instance variables should be prefixed with an underscore (just like when implicitly synthesized).

Expressions

• Use object literals, boxed expressions, and subscripting over the older, grosser alternatives.
• Comparisons should be explicit for everything except BOOLs.
• Prefer positive comparisons to negative.
• There shouldn't be a space between a cast and the variable being cast.

NewType a = (OldType)b;

Control Structures

• Always surround if bodies with curly braces if there is an else. Single-line if bodies without an else should be on the same line as the if.
• All curly braces should begin on the same line as their associated statement. They should end on a new line.
• Put a single space after keywords and before their parentheses.
• Return and break early.
• No spaces between parentheses and their contents.

if (shitIsBad) return;

if (something == nil) {
	// do stuff
} else {
	// do other stuff
}

Blocks

• Blocks should have a space between their return type and name.
• Block definitions should omit their return type when possible.
• Block definitions should omit their arguments if they are void.

void (^blockName1)(void) = ^{
   // do some things
};

id (^blockName2)(id) = ^ id (id args) {
   // do some things
};

Literals

• The contents of array and dictionary literals should have a space on both sides.
• Dictionary literals should have no space between the key and the colon, and a single space between colon and value.

NSArray *theShit = @[ @1, @2, @3 ];

NSDictionary *keyedShit = @{ GHDidCreateStyleGuide: @YES };

Categories

• Categories should be named for the sort of functionality they provide. Don't create umbrella categories.
• Category methods should always be prefixed.
• If you need to expose private methods for subclasses or unit testing, create a class extension named Class+Private.