Google Objective C Style Detailed

Google Objective-C Style (Detailed)

Source: https://google.github.io/styleguide/objcguide.html

Pair with the quick reference: google-objective-c-style

This skill expands the short skill with section-level rules from Google's guide. For authoritative full text, see the official URL and reference.md.

How to use

1. Start from google-objective-c-style for everyday edits
2. Use this skill for reviews, ambiguous cases, or API/doc conventions
3. Consult reference.md for source paths and supplemental docs

Section rules

import <Foundation/Foundation.h>

• A sample class demonstrating good Objective-C style. All interfaces,
• categories, and protocols (read: all non-trivial top-level declarations
• in a header) MUST be commented. Comments must also be adjacent to the
• object they're documenting.
• Convenience creation method.
• See -initWithBar: for details about @c bar.
• @param bar The string for fooing.
• @return An instance of Foo.
• Initializes and returns a Foo object using the provided Bar instance.
• @param bar A string that represents a thing that does a thing.

import "Shared/Util/Foo.h"

• (instancetype)initWithBar:(Bar *)bar {
• (BOOL)doWorkWithBlah:(NSString *)blah {

Category Naming

• (nullable NSData *)gtm_encodedState;

Objective-C Method Names

• (void)addTarget:(id)target action:(SEL)action; // GOOD; no conjunction needed
• (CGPoint)convertPoint:(CGPoint)point fromView:(UIView *)view; // GOOD; conjunction clarifies parameter
• (Sandwich *)sandwich; // GOOD.
• (CGFloat)height; // GOOD.
• (CGFloat)calculateHeight; // AVOID.
• (id)theDelegate; // AVOID.
• (id)delegate; // GOOD.
• (id)getDelegate; // AVOID.

File Comments

• License boilerplate if necessary. Choose the appropriate boilerplate for the
• A basic description of the contents of the file if necessary.

Declaration Comments

• A delegate for NSApplication to handle notifications about app
• launch and shutdown. Owned by the main app controller.
• The background task in progress, if any. This is initialized
• to the value UIBackgroundTaskInvalid.

Approved Nonstandard Extensions

• The attribute keyword is approved as it is used in Apple API
• The binary form of the conditional operator, A ?: B, is approved.

Avoid Messaging the Current Object Within Initializers and -dealloc

• Methods can be overridden in subclasses, either deliberately, or
• When editing a helper method, it may not be obvious that the code is being

Mutables, Copies and Ownership

• (NSArray *)listOfThings {
• (SomeProtoMessage *)someMessageForValue:(BOOL)value {

Copy Potentially Mutable Objects

• (void)setFilters:(NSSet<FilterThing *> *)filters {
• (NSArray<ContentThing *> *)currentContent {
• (void)setFooMessage:(FooMessage *)fooMessage {
• (FooMessage *)fooMessage {
• (void)doSomethingWithThings:(NSArray<Thing *> *)things {

Nullability

• (nonnull instancetype)initWithTitle:(nonnull NSString *)title

Method Declarations and Definitions

• (void)doSomethingWithString:(NSString *)theString {

Function Declarations and Definitions

• The opening parenthesis must always be on the same line as the function
• If you cannot fit the return type and the function name on a single line,
• There should never be a space before the opening parenthesis.
• There should never be a space between function parentheses and parameters.
• The open curly brace is always on the end of the last line of the function
• The close curly brace is either on the last line by itself or on the same
• There should be a space between the close parenthesis and the open curly
• All parameters should be aligned if possible.
• Function scopes should be indented 2 spaces.
• Wrapped parameters should have a 4 space indent.