Domain Objective-C styleguide

Status

This style guide is no longer being maintained.

Brace style

Egyptian braces are to be used

Incorrect

-(void)myMethodName
{

 if (myCondition)
 {
   
 }
}

###Correct

-(void)myMethodName{

 if (myCondition){
   
 }
}

---

Else and If Else statements follow on the same line as the previous statement's closing brace.

Incorrect

if (myCondition) {

}
else if (myOtherCondition) {

}
else {

}

###Correct

if (myCondition) {

} else if (myOtherCondition) {

} else {

}

Assignment alignment

Align all assignment operators if possible.

###Incorrect

myObjectWithLongName = 16
myVarWithShortName = anotherObject
superShort = @"wicked"

###Correct

myObjectWithLongName   = 16
myVarWithShortName     = anotherObject
superShort             = @"wicked"

Tabs or spaces

Always use the Xcode default of 4 spaces.

Method naming

Avoid "and" or “with” for multiple method parameters.

###Incorrect

[self goDoSomethingWithThing:myThing andStuff:myStuff];

###Correct

[self goDoSomethingWithThing:myThing stuff:myStuff];

---

Make the word before the argument describe the argument.

###Incorrect

[self withThingDoSomething:myThing andStuff:myStuff];

###Correct

[self goDoSomethingWithThing:myThing stuff:myStuff];

---

Setters set, getters don’t get.

###Incorrect

-(void)size:(CGSize)size;
-(CGSize)getSize;

###Correct

-(void)setSize:(CGSize)size;
-(CGSize)size;

---

Boolean naming should contain "can", "will", "should" or "is”.

###Incorrect

-(BOOL)doesDisplay;

###Correct

-(BOOL)canDisplay;
-(BOOL)willDisplay;
-(BOOL)shouldDisplay;
-(BOOL)isDisplaying;

---

Acronyms are capitalized (not just methods). "Id" is not an acronym.

###Incorrect

-(void)makeRequestWithUrl;

###Correct

-(void)makeRequestWithURL;

iVars and properties

• Private iVars belong in a blank category in the implementation file NOT the header.
• Protected iVars belong in the header with @protected keyword. (so it doesn’t look like private iVars placed incorectly)
• Use protected iVars for subclass use. NOT properties.

---

Use a leading underscore for all iVars

###Incorrect

UIView* myView;

###Correct

UIView* _myView;

---

Access properties by iVar backer in implementation file. The dot accessor is for external use only.

###Incorrect

self.myView = [[UIView alloc] init];

###Correct

_myView = [[UIView alloc] init];

Enums

NS_ENUM should be used instead of enum.

###Incorrect

typedef enum {
    ExampleStyle_None,
    ExampleStyle_Short,
} ExampleStyle;

###Correct

typedef NS_ENUM(NSInteger, ExampleStyle) {
    ExampleStyle_None,
    ExampleStyle_Short,
};

---

• Enums should be typed using typedef
• Each enum item name should be prefixed with the type name followed by an underscore

###Incorrect

typedef NS_ENUM(NSInteger, CellHeight) {
    Default,
    Short,
    Tall,
};

###Correct

typedef NS_ENUM(NSInteger, CellHeight) {
    CellHeight_Default,
    CellHeight_Short,
    CellHeight_Tall,
};

Boolean comparisons

Don’t compare against YES or NO.

###Incorrect

if (myBOOL == YES)
if (myBOOL == NO)

###Correct

if (myBOOL)
if (!myBOOL)

Dot notation

Dot notation is to be used at all available opportunities unless explicitly frowned-upon by this styleguide.

Import/Include

Import Objective-C

Include C/C++

Golden Trails

Fail early instead of forcing an obscure trail of logic.

###Incorrect

if (condition1){
       if (condition2){
           if (condition3){
               //only logic
           }
       }
   }

###Correct

if (!condition1) return;

NSError handling

Any method that takes an NSError by reference should also return a Boolean. Evaluate the error if the method returned false.

###Incorrect

NSError *error;
[self trySomethingWithError:&error];
if (error) {
   // Handle Error
}

###Correct

NSError *error;
if (![self trySomethingWithError:&error]) {
   // Handle Error
}

Blocks

Type your blocks whenever possible.

###Incorrect

- (void)someMethodThatTakesABlock:(returnType (^)(parameterTypes))myBlockParamName {...}

###Correct

typedef returnType (^myBlockTypeName)(parameterTypes);
- (void)someMethodThatTakesABlock:(myBlockTypeName)myBlockParamName;

Methods requiring a super call

Always mark the method with the required super attribute.

###Incorrect

- (void)someMethodThatBreaksIfSuperIsNotCalled;

###Correct

- (void)someMethodThatBreaksIfSuperIsNotCalled __attribute__((objc_requires_super));

Deprecating Methods

Always mark the method with the deprecated attribute or a deprecation method.

###Incorrect

- (void)someDeprecatedMethod;

###Correct

- (void)someDeprecatedMethod __attribute__((deprecated));

Custom constructor

Always use instancetype, not id, as the return type.

###Incorrect

- (id)init;

###Correct

- (instancetype)init;

Literals

Always use literals.

###Incorrect

[myArray objectAtIndex:4];

###Correct

myArray[4];

Array first and last object

Always use firstObject / lastObject to avoid out of bounds for an empty array.

###Incorrect

myArray[0]

###Correct

[myArray firstObject]

constants

Always use a leading 'k' in your constant variable name.

###Incorrect

static const NSInteger myAwesomeConstant = 17;

###Correct

static const NSInteger kMyAwesomeConstant = 17;

Turnery operators

Wrap the conditional in parentheses and leave a space on either side of all operators.

###Incorrect

label.text = isAwesome? @"awesome": @"lame";

###Correct

label.text = (isAwesome) ? @"awesome" : @"lame";

Scalars

Don't use platform or bit-size specific scalars unless explicitly needed.

###Incorrect

int myInt      = 16;
float myFloat  = 1.0f;

###Correct

NSInteger myInt  = 16;
CGFloat myFloat  = 1.0f;

###Correct

UInt8 mySmallInt = 4; // I really need an 8-bit integer here for the following reasons...

The 'new' constructor

Do not use the new constructor.

###Incorrect

NSObject* myObject = [NSObject new];

###Correct

NSObject* myObject = [[NSObject alloc] init];

Class names

• Use the correct design pattern use name in the class name. Do not use the word 'manager'.
• Include the correct Domain prefix. If working on any other project include the brand/project prefix in the class name.

###Incorrect

UserBehaviourManager

###Correct

DMUserBehaviourController

###Correct

DMABCUserBehaviourModel

Commenting

Use double leading asterisks for block comments. Block comments should be used to clarify the intent of a method.

###Incorrect

-(void)myMethod{
/* this method does ... */

}

###Correct

/** this method does ... */ 
-(void)myMethod{

}

---

Use inline comments for clarifying the use of obscure methods/functions or to explain why you've used a non-standard technique. Inline comments should fall above their subject on their own line.

###Incorrect

// this method does ...
-(void)myMethod{
 [self doSomethingElse]; //go and do something else

}

###Correct

-(void)myMethod{
//normally technique A should be used here but 
//because of [reason] technique B must be used. 

//getting the square root of PI
sqrtf(M_PI);
}

---

Use pipes to identify symbols within a comment.

###Incorrect

-(void)myMethod{
 //myInt is used to calculate the meaning of life.
 NSInteger myInt = 42;
}

###Correct

-(void)myMethod{
 //|myInt| is used to calculate the meaning of life.
 NSInteger myInt = 42;
}

Delegate methods

When creating a component that uses delegation include a reference to that component through it’s delegate methods. Try to use the component name, excluding the prefix, at the start of each delegate method whenever possible. The component will be called “DMPickerView” for this example.

###Incorrect

-(void)didPressItemAtIndex:(NSUInteger)itemIndex;

###Correct

-(void)pickerView:(DMPickerView *)pickerView  didPressItemAtIndex:(NSUInteger)itemIndex;

---

Delegate method names should contain "did", "should" or "will”.

###Incorrect

-(void)pickerMayStartBehaviour:(DMPickerView *)pickerView;

###Correct

-(void)pickerDidStartBehaviour:(DMPickerView *)pickerView;

Localizable strings key format

Localizable strings keys should provide usage context without using the value.

###Incorrect

"CONTACT_TABLE_DISMISS_CONFIRM_BUTTON_TOTALLY" = "Totally"

###Incorrect

"CONTACT_TABLE_DISMISS_CONFIRM_BUTTON" = "Totally"

###Correct

"contact-table.dismiss-confirm-button" = "Totally"

Component thread safety

When creating components that use blocks or protocols that use multi-threading, always return them on the main thread unless otherwise specified. This is to ensure that the user of the component will always know what thread the blocks or protocols will return on (main) and to ensure that the component itself is responsible for it’s own thread management.

###Incorrect

-(void)myMethod {

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
       id data = [self someLargeCalculations];
       [_delegate myProtocolMethod:data];
   });
}

-(void)anotherMethod:(MyBlockType)myBlock {

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
   id data = [self someLargeCalculations];        
   myBlock(data);
   });
}

###Correct

-(void)myMethod {

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
       id data = [self someLargeCalculations];

       dispatch_async(dispatch_get_main_queue(), ^{
           
           [_delegate myProtocolMethod:data];
       });
   });
}

-(void)anotherMethod:(MyBlockType)myBlock {

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
   id data = [self someLargeCalculations];  

       dispatch_async(dispatch_get_main_queue(), ^{      

          	    myBlock(data);
       });
   });
}