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https://github.com/spotify/ios-style

Guidelines for iOS development in use at Spotify
https://github.com/spotify/ios-style

code-style coding-style objective-c spotify style-guide

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Guidelines for iOS development in use at Spotify

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README 

        
Spotify Objective-C Coding Style

================================



Version: 0.9.0



Our general coding conventions at Spotify are documented on an internal wiki, but specifics for Objective-C and

Objective-C++ code in the iOS client are documented here.



License

-------

Copyright (c) 2015-2016 Spotify AB. 



This work is licensed under a [Creative Commons Attribution 4.0 International License]( http://creativecommons.org/licenses/by/4.0/).



Table of Contents

-----------------



1.  [Spacing, Lines and Formatting](#spacing-lines-and-formatting)

2.  [Brackets](#brackets)

3.  [Naming](#naming)

4.  [Comments](#comments)

5.  [Pragma Marks](#pragma-marks)

6.  [Constants](#constants)

7.  [Return Early](#return-early)

8.  [Initializers](#initializers)

9.  [Headers](#headers)

10. [Nullability](#nullability)

11. [Strings](#strings)

12. [Dot Notation](#dot-notation)

13. [Categories](#categories)



Spacing, Lines and Formatting

-----------------------------



### Line length

* Keep your lines within **120** characters width when possible.

  * In Xcode, you can set a page guide in Text Editing in Preferences.



### Whitespace

* Use **4** spaces for indentation and alignment. Do not use tabs.

* Trailing whitespace is acceptable only on blank lines, but discouraged even there.

  * In Xcode, select "Automatically trim whitespace" and "Including whitespace-only lines" in Text Editing preferences

    to handle this automatically.

* Put spaces after commas, and before and after operators.

* Do not put spaces between parentheses and what they are enclosing.



**Example:**

```objc

foo("bar") 

```



**Not:**



```objc

foo( "bar" )

```



### Containers

* Array one-liners are acceptable unless they have too many items or their values are too long.



```objc

NSArray *array = @[@"uno", @"dos", @"tres", @"cuatro"];

```



* In that case, break them in several lines:



```objc

NSArray *array = @[

    @"This is how we do, yeah, chilling, laid back",

    @"Straight stuntin’ yeah we do it like that",

    @"This is how we do, do do do do, this is how we do",

];

```



* Dictionary one-liners are reserved for single pairs only:



```objc

NSDictionary *dict = @{@"key" : @"highway"};

```



* Format it pretty otherwise, leaving a trailing comma after the last item:

```objc

NSDictionary *dict = @{

    @"key1" : @"highway",

    @"key2" : @"heart",

};

```



Brackets

--------

* Always use brackets for `if` / `for` / `while` / `do`-`while` statements. Even if its a one-liner:



```objc

if (itsMagic) {

    [self makeItEverlasting];

}

```



* Write follow up `else` clauses after the previous closing bracket on the same line.



```objc

if (hasClue) {

    knowExactlyWhatToDo();

} else if (seeItAllSoClear) {

    writeItDown();

} else {

    sing();

    dance();

}

```



Naming

------

* Follow Apple’s [Coding Guidelines for Cocoa](https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CodingGuidelines/CodingGuidelines.html)

on naming.



Comments

--------

* Use the `//` style for single line comments or when appending comments in the same line of code.

* Use the `/* */` style for multi-line comments.



**Example:**

```objc

/*

 This is a multi-line comment. The opening and closing markers are on their

 own lines.



 This is a new paragraph in the same block comment.

 */



stop(); // Hammer-time!



// this is a very brief comment.

```



* Document all methods and properties in the headers using Xcode’s documentation style (which is `///` at the time of writing). 

You can select a property or method and use `Option`+`Cmd`+`/` to generate the documentation template for it. Make sure to use the available 

markup tags like `@param`, `@return`, etc. (these will be auto-generated for you by Xcode).



Pragma Marks

------------

* Use the pre-processor instruction `#pragma mark` to mark related groups of methods.



Constants

---------

* Do not define constants using `#define`.

* Publicly (or privately) exposed variables should be constant (trying to assign values will result in compilation

error).



```objc

extern NSString * const SPTCodeStandardErrorDomain;

```



Return Early

------------

* Return early on errors and failed pre-conditions to avoid unnecessary nested brackets and / or unnecessary

computations.



**Example:**



```objc

- (void)setFireToTheRain:(id)rain

{

    if ([_rain isEqualTo:rain]) {

        return;

    }



    _rain = rain;

}

```



Initializers

------------

* Follow [Apple's typical init format](https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/EncapsulatingData/EncapsulatingData.html#//apple_ref/doc/uid/TP40011210-CH5-SW11) to initialize objects.



**Example:**



```objc

- (instancetype)init 

{

    self = [super init];

 

    if (self) {

        // initialize instance variables here

    }

 

    return self;

}

```



Headers

-------

* The use of prefix headers has been deprecated. Do not add new code to an existing prefix header.

* When importing a module use the hash-import variant instead of at-import.

  * Yes: `#import `

  * No: `@import Foundation;`



Nullability

-----------

* Use `NS_ASSUME_NONNULL_BEGIN` and `NS_ASSUME_NONNULL_END` in header files, and explicitly add `nullable` when needed. Example:

```objc

#import 



@protocol SPTPlaylist;



NS_ASSUME_NONNULL_BEGIN



typedef void(^SPTSomeBlock)(NSData * _Nullable data, NSError * _Nullable error);



@interface SPTYourClass : NSObject



@property (nonatomic, copy, readonly, nullable) NSString *customTitle;

@property (nonatomic, strong, readonly) id playlist;



- (nullable instancetype)initWithPlaylist:(id)playlist

                              customTitle:(nullable NSString *)customTitle;



@end



NS_ASSUME_NONNULL_END

```



Strings

-------

* All strings presented to the user should be localized.



Dot Notation

------------

* Use bracket notation when calling non-accessor methods:



```objc

[self doSomething];

```



* Use bracket notation when accessing globals through a class method:



```objc

[MyClass sharedInstance];

```



* Set and access properties using dot notation:



```objc

self.myString = @"A string";

```



* Except in the `init` or `dealloc` methods, always use the ivar directly there:



```objc

_myString = nil;

```



Categories

----------

* Methods in categories on non-Spotify classes must be prefixed `spt_` to avoid name clashes.