Coding conventions for Objective-C projects
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README.md

README.md

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).

Control Structures

  • Comparisons should be explicit for everything except BOOLs.
  • Prefer positive comparisons to negative.
  • 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 (something == nil) {
    // do stuff
} else {
    // do other stuff
}

if (shitIsBad) return;

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.