Objective-C

When code needs to be written in Objective-C, we use source files with an .mm extension, which denotes the Objective-C++ file type to the compiler. This allows to mix Objective-C and C++ code in the same file. All the C++ coding conventions listed above apply to Objective-C accordingly, but there are some additional rules for special syntax elements. In general, demo code snippets from Apple’s documentation need to be reformatted to match our coding conventions.

Spacing

Declarations and definitions of class and instance methods require a space before the return type (in brackets) and each selector element, but nowhere else.

Example: Declaring Instance Methods

// Right
- (void)observeValueForKeyPath:(NSString*)keyPath ofObject:(id)object change:(NSDictionary<NSString*,id>*)change context:(void*)context;

// Wrong
-(void) observeValueForKeyPath: (NSString *)keyPath ofObject: (id)object change: (NSDictionary<NSString *,id> *)change context: (void *)context;

When nesting method calls, no additional spaces are inserted.

Example: Calling Instance Methods

// Right
NSURL* tempFileURL = [[[NSURL fileURLWithPath:NSTemporaryDirectory () isDirectory:YES] URLByAppendingPathComponent:uniqueString] URLByAppendingPathExtension:@"mov"];

// Wrong
NSURL* tempFileURL = [ [ [NSURL fileURLWithPath:NSTemporaryDirectory () isDirectory:YES ] URLByAppendingPathComponent:uniqueString ] URLByAppendingPathExtension:@"mov" ];

Line Breaks

We do not insert line breaks to create a table like appearance for decalarations, simply use one long line.

Example: Instance Methods

// Wrong
- (void)observeValueForKeyPath: (NSString*)keyPath
                      ofObject: (id)object
                        change: (NSDictionary<NSString*,id>*)change
                       context: (void*)context;

For block parameters use a new line for the opening bracket.

Example: Passing a Block Parameter Value

// Right
[AVCaptureDevice requestAccessForMediaType:AVMediaTypeAudio completionHandler:^(BOOL granted)
{
    requestPending = false;
}];

// Wrong
[AVCaptureDevice requestAccessForMediaType:AVMediaTypeAudio completionHandler:^(BOOL granted){
    requestPending = false;
}
];

Literals

When available, use the appropriate literals for Objetive-C types.

Example: Some Objective-C Literals

// Right
NSString* message = nil;
BOOL success = YES;

// Wrong
NSString* message = 0;
BOOL success = false;