The official raywenderlich.com Objective-C style guide.

This style guide outlines the coding conventions for raywenderlich.com.

Introduction

The reason we made this style guide was so that we could keep the code in our books, tutorials, and starter kits nice and consistent - even though we have many different authors working on the books.

This style guide is different from other Objective-C style guides you may see, because the focus is centered on readability for print and the web. Many of the decisions were made with an eye toward conserving space for print, easy legibility, and tutorial writing.

Credits

The creation of this style guide was a collaborative effort from various raywenderlich.com team members under the direction of Nicholas Waynik. The team includes: Soheil Moayedi AzarpourRicardo Rendon CepedaTony DahburaColin EberhardtMatt GallowayGreg HeoMatthijs HollemansChristopher LaPolloSaul MoraAndy PereiraMic PringlePietro ReaCesare RocchiMarin TodorovNicholas Waynik, and Ray Wenderlich

We would like to thank the creators of the New York Times and Robots & Pencils' Objective-C Style Guides. These two style guides provided a solid starting point for this guide to be created and based upon.

Background

Here are some of the documents from Apple that informed the style guide. If something isn't mentioned here, it's probably covered in great detail in one of these:

Table of Contents

Language

US English should be used.

Preferred:

UIColor *myColor = [UIColor whiteColor];

Not Preferred:

UIColor *myColour = [UIColor whiteColor];

Code Organization

Use #pragma mark - to categorize methods in functional groupings and protocol/delegate implementations following this general structure.

#pragma mark - Lifecycle

- (instancetype)init {}
- (void)dealloc {}
- (void)viewDidLoad {}
- (void)viewWillAppear:(BOOL)animated {}
- (void)didReceiveMemoryWarning {} #pragma mark - Custom Accessors - (void)setCustomProperty:(id)value {}
- (id)customProperty {} #pragma mark - IBActions - (IBAction)submitData:(id)sender {} #pragma mark - Public - (void)publicMethod {} #pragma mark - Private - (void)privateMethod {} #pragma mark - Protocol conformance
#pragma mark - UITextFieldDelegate
#pragma mark - UITableViewDataSource
#pragma mark - UITableViewDelegate #pragma mark - NSCopying - (id)copyWithZone:(NSZone *)zone {} #pragma mark - NSObject - (NSString *)description {}

Spacing

  • Indent using 2 spaces (this conserves space in print and makes line wrapping less likely). Never indent with tabs. Be sure to set this preference in Xcode.
  • Method braces and other braces (if/else/switch/while etc.) always open on the same line as the statement but close on a new line.

Preferred:

if (user.isHappy) {
//Do something
} else {
//Do something else
}

Not Preferred:

if (user.isHappy)
{
//Do something
}
else {
//Do something else
}
  • There should be exactly one blank line between methods to aid in visual clarity and organization. Whitespace within methods should separate functionality, but often there should probably be new methods.
  • Prefer using auto-synthesis. But if necessary, @synthesize and @dynamic should each be declared on new lines in the implementation.
  • Colon-aligning method invocation should often be avoided. There are cases where a method signature may have >= 3 colons and colon-aligning makes the code more readable. Please do NOThowever colon align methods containing blocks because Xcode's indenting makes it illegible.

Preferred:

// blocks are easily readable
[UIView animateWithDuration:1.0 animations:^{
// something
} completion:^(BOOL finished) {
// something
}];

Not Preferred:

// colon-aligning makes the block indentation hard to read
[UIView animateWithDuration:1.0
animations:^{
// something
}
completion:^(BOOL finished) {
// something
}];

Comments

When they are needed, comments should be used to explain why a particular piece of code does something. Any comments that are used must be kept up-to-date or deleted.

Block comments should generally be avoided, as code should be as self-documenting as possible, with only the need for intermittent, few-line explanations. Exception: This does not apply to those comments used to generate documentation.

Naming

Apple naming conventions should be adhered to wherever possible, especially those related to memory management rules (NARC).

Long, descriptive method and variable names are good.

Preferred:

UIButton *settingsButton;

Not Preferred:

UIButton *setBut;

A three letter prefix should always be used for class names and constants, however may be omitted for Core Data entity names. For any official raywenderlich.com books, starter kits, or tutorials, the prefix 'RWT' should be used.

Constants should be camel-case with all words capitalized and prefixed by the related class name for clarity.

Preferred:

static NSTimeInterval const RWTTutorialViewControllerNavigationFadeAnimationDuration = 0.3;

Not Preferred:

static NSTimeInterval const fadetime = 1.7;

Properties should be camel-case with the leading word being lowercase. Use auto-synthesis for properties rather than manual @synthesize statements unless you have good reason.

Preferred:

@property (strong, nonatomic) NSString *descriptiveVariableName;

Not Preferred:

id varnm;

Underscores

When using properties, instance variables should always be accessed and mutated using self.. This means that all properties will be visually distinct, as they will all be prefaced with self..

An exception to this: inside initializers, the backing instance variable (i.e. _variableName) should be used directly to avoid any potential side effects of the getters/setters.

Local variables should not contain underscores.

Methods

In method signatures, there should be a space after the method type (-/+ symbol). There should be a space between the method segments (matching Apple's style). Always include a keyword and be descriptive with the word before the argument which describes the argument.

The usage of the word "and" is reserved. It should not be used for multiple parameters as illustrated in theinitWithWidth:height: example below.

Preferred:

- (void)setExampleText:(NSString *)text image:(UIImage *)image;
- (void)sendAction:(SEL)aSelector to:(id)anObject forAllCells:(BOOL)flag;
- (id)viewWithTag:(NSInteger)tag;
- (instancetype)initWithWidth:(CGFloat)width height:(CGFloat)height;

Not Preferred:

-(void)setT:(NSString *)text i:(UIImage *)image;
- (void)sendAction:(SEL)aSelector :(id)anObject :(BOOL)flag;
- (id)taggedView:(NSInteger)tag;
- (instancetype)initWithWidth:(CGFloat)width andHeight:(CGFloat)height;
- (instancetype)initWith:(int)width and:(int)height; // Never do this.

Variables

Variables should be named as descriptively as possible. Single letter variable names should be avoided except in for() loops.

Asterisks indicating pointers belong with the variable, e.g., NSString *text not NSString* text orNSString * text, except in the case of constants.

Private properties should be used in place of instance variables whenever possible. Although using instance variables is a valid way of doing things, by agreeing to prefer properties our code will be more consistent.

Direct access to instance variables that 'back' properties should be avoided except in initializer methods (initinitWithCoder:, etc…), dealloc methods and within custom setters and getters. For more information on using Accessor Methods in Initializer Methods and dealloc, see here.

Preferred:

@interface RWTTutorial : NSObject

@property (strong, nonatomic) NSString *tutorialName;

@end

Not Preferred:

@interface RWTTutorial : NSObject {
NSString *tutorialName;
}

Property Attributes

Property attributes should be explicitly listed, and will help new programmers when reading the code. The order of properties should be storage then atomicity, which is consistent with automatically generated code when connecting UI elements from Interface Builder.

Preferred:

@property (weak, nonatomic) IBOutlet UIView *containerView;
@property (strong, nonatomic) NSString *tutorialName;

Not Preferred:

@property (nonatomic, weak) IBOutlet UIView *containerView;
@property (nonatomic) NSString *tutorialName;

Properties with mutable counterparts (e.g. NSString) should prefer copy instead of strong. Why? Even if you declared a property as NSString somebody might pass in an instance of an NSMutableStringand then change it without you noticing that.

Preferred:

@property (copy, nonatomic) NSString *tutorialName;

Not Preferred:

@property (strong, nonatomic) NSString *tutorialName;

Dot-Notation Syntax

Dot syntax is purely a convenient wrapper around accessor method calls. When you use dot syntax, the property is still accessed or changed using getter and setter methods. Read more here

Dot-notation should always be used for accessing and mutating properties, as it makes code more concise. Bracket notation is preferred in all other instances.

Preferred:

NSInteger arrayCount = [self.array count];
view.backgroundColor = [UIColor orangeColor];
[UIApplication sharedApplication].delegate;

Not Preferred:

NSInteger arrayCount = self.array.count;
[view setBackgroundColor:[UIColor orangeColor]];
UIApplication.sharedApplication.delegate;

Literals

NSStringNSDictionaryNSArray, and NSNumber literals should be used whenever creating immutable instances of those objects. Pay special care that nil values can not be passed into NSArrayand NSDictionary literals, as this will cause a crash.

Preferred:

NSArray *names = @[@"Brian", @"Matt", @"Chris", @"Alex", @"Steve", @"Paul"];
NSDictionary *productManagers = @{@"iPhone": @"Kate", @"iPad": @"Kamal", @"Mobile Web": @"Bill"};
NSNumber *shouldUseLiterals = @YES;
NSNumber *buildingStreetNumber = @10018;

Not Preferred:

NSArray *names = [NSArray arrayWithObjects:@"Brian", @"Matt", @"Chris", @"Alex", @"Steve", @"Paul", nil];
NSDictionary *productManagers = [NSDictionary dictionaryWithObjectsAndKeys: @"Kate", @"iPhone", @"Kamal", @"iPad", @"Bill", @"Mobile Web", nil];
NSNumber *shouldUseLiterals = [NSNumber numberWithBool:YES];
NSNumber *buildingStreetNumber = [NSNumber numberWithInteger:10018];

Constants

Constants are preferred over in-line string literals or numbers, as they allow for easy reproduction of commonly used variables and can be quickly changed without the need for find and replace. Constants should be declared as static constants and not #defines unless explicitly being used as a macro.

Preferred:

static NSString * const RWTAboutViewControllerCompanyName = @"RayWenderlich.com";

static CGFloat const RWTImageThumbnailHeight = 50.0;

Not Preferred:

#define CompanyName @"RayWenderlich.com"

#define thumbnailHeight 2

Enumerated Types

When using enums, it is recommended to use the new fixed underlying type specification because it has stronger type checking and code completion. The SDK now includes a macro to facilitate and encourage use of fixed underlying types: NS_ENUM()

For Example:

typedef NS_ENUM(NSInteger, RWTLeftMenuTopItemType) {
RWTLeftMenuTopItemMain,
RWTLeftMenuTopItemShows,
RWTLeftMenuTopItemSchedule
};

You can also make explicit value assignments (showing older k-style constant definition):

typedef NS_ENUM(NSInteger, RWTGlobalConstants) {
RWTPinSizeMin = 1,
RWTPinSizeMax = 5,
RWTPinCountMin = 100,
RWTPinCountMax = 500,
};

Older k-style constant definitions should be avoided unless writing CoreFoundation C code (unlikely).

Not Preferred:

enum GlobalConstants {
kMaxPinSize = 5,
kMaxPinCount = 500,
};

Case Statements

Braces are not required for case statements, unless enforced by the complier.
When a case contains more than one line, braces should be added.

switch (condition) {
case 1:
// ...
break;
case 2: {
// ...
// Multi-line example using braces
break;
}
case 3:
// ...
break;
default:
// ...
break;
}

There are times when the same code can be used for multiple cases, and a fall-through should be used. A fall-through is the removal of the 'break' statement for a case thus allowing the flow of execution to pass to the next case value. A fall-through should be commented for coding clarity.

switch (condition) {
case 1:
// ** fall-through! **
case 2:
// code executed for values 1 and 2
break;
default:
// ...
break;
}

When using an enumerated type for a switch, 'default' is not needed. For example:

RWTLeftMenuTopItemType menuType = RWTLeftMenuTopItemMain;

switch (menuType) {
case RWTLeftMenuTopItemMain:
// ...
break;
case RWTLeftMenuTopItemShows:
// ...
break;
case RWTLeftMenuTopItemSchedule:
// ...
break;
}

Private Properties

Private properties should be declared in class extensions (anonymous categories) in the implementation file of a class. Named categories (such as RWTPrivate or private) should never be used unless extending another class. The Anonymous category can be shared/exposed for testing using the +Private.h file naming convention.

For Example:

@interface RWTDetailViewController ()

@property (strong, nonatomic) GADBannerView *googleAdView;
@property (strong, nonatomic) ADBannerView *iAdView;
@property (strong, nonatomic) UIWebView *adXWebView; @end

Booleans

Objective-C uses YES and NO. Therefore true and false should only be used for CoreFoundation, C or C++ code. Since nil resolves to NO it is unnecessary to compare it in conditions. Never compare something directly to YES, because YES is defined to 1 and a BOOL can be up to 8 bits.

This allows for more consistency across files and greater visual clarity.

Preferred:

if (someObject) {}
if (![anotherObject boolValue]) {}

Not Preferred:

if (someObject == nil) {}
if ([anotherObject boolValue] == NO) {}
if (isAwesome == YES) {} // Never do this.
if (isAwesome == true) {} // Never do this.

If the name of a BOOL property is expressed as an adjective, the property can omit the “is” prefix but specifies the conventional name for the get accessor, for example:

@property (assign, getter=isEditable) BOOL editable;

Text and example taken from the Cocoa Naming Guidelines.

Conditionals

Conditional bodies should always use braces even when a conditional body could be written without braces (e.g., it is one line only) to prevent errors. These errors include adding a second line and expecting it to be part of the if-statement. Another, even more dangerous defect may happen where the line "inside" the if-statement is commented out, and the next line unwittingly becomes part of the if-statement. In addition, this style is more consistent with all other conditionals, and therefore more easily scannable.

Preferred:

if (!error) {
return success;
}

Not Preferred:

if (!error)
return success;

or

if (!error) return success;

Ternary Operator

The Ternary operator, ?: , should only be used when it increases clarity or code neatness. A single condition is usually all that should be evaluated. Evaluating multiple conditions is usually more understandable as an if statement, or refactored into instance variables. In general, the best use of the ternary operator is during assignment of a variable and deciding which value to use.

Non-boolean variables should be compared against something, and parentheses are added for improved readability. If the variable being compared is a boolean type, then no parentheses are needed.

Preferred:

NSInteger value = 5;
result = (value != 0) ? x : y; BOOL isHorizontal = YES;
result = isHorizontal ? x : y;

Not Preferred:

result = a > b ? x = c > d ? c : d : y;

Init Methods

Init methods should follow the convention provided by Apple's generated code template. A return type of 'instancetype' should also be used instead of 'id'.

- (instancetype)init {
self = [super init];
if (self) {
// ...
}
return self;
}

See Class Constructor Methods for link to article on instancetype.

Class Constructor Methods

Where class constructor methods are used, these should always return type of 'instancetype' and never 'id'. This ensures the compiler correctly infers the result type.

@interface Airplane
+ (instancetype)airplaneWithType:(RWTAirplaneType)type;
@end

More information on instancetype can be found on NSHipster.com.

CGRect Functions

When accessing the xywidth, or height of a CGRect, always use the CGGeometry functionsinstead of direct struct member access. From Apple's CGGeometry reference:

All functions described in this reference that take CGRect data structures as inputs implicitly standardize those rectangles before calculating their results. For this reason, your applications should avoid directly reading and writing the data stored in the CGRect data structure. Instead, use the functions described here to manipulate rectangles and to retrieve their characteristics.

Preferred:

CGRect frame = self.view.frame;

CGFloat x = CGRectGetMinX(frame);
CGFloat y = CGRectGetMinY(frame);
CGFloat width = CGRectGetWidth(frame);
CGFloat height = CGRectGetHeight(frame);
CGRect frame = CGRectMake(0.0, 0.0, width, height);

Not Preferred:

CGRect frame = self.view.frame;

CGFloat x = frame.origin.x;
CGFloat y = frame.origin.y;
CGFloat width = frame.size.width;
CGFloat height = frame.size.height;
CGRect frame = (CGRect){ .origin = CGPointZero, .size = frame.size };

Golden Path

When coding with conditionals, the left hand margin of the code should be the "golden" or "happy" path. That is, don't nest if statements. Multiple return statements are OK.

Preferred:

- (void)someMethod {
if (![someOther boolValue]) {
return;
} //Do something important
}

Not Preferred:

- (void)someMethod {
if ([someOther boolValue]) {
//Do something important
}
}

Error handling

When methods return an error parameter by reference, switch on the returned value, not the error variable.

Preferred:

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

Not Preferred:

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

Some of Apple’s APIs write garbage values to the error parameter (if non-NULL) in successful cases, so switching on the error can cause false negatives (and subsequently crash).

Singletons

Singleton objects should use a thread-safe pattern for creating their shared instance.

+ (instancetype)sharedInstance {
static id sharedInstance = nil; static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[self alloc] init];
}); return sharedInstance;
}

This will prevent possible and sometimes prolific crashes.

Line Breaks

Line breaks are an important topic since this style guide is focused for print and online readability.

For example:

self.productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:productIdentifiers];

A long line of code like this should be carried on to the second line adhering to this style guide's Spacing section (two spaces).

self.productsRequest = [[SKProductsRequest alloc]
initWithProductIdentifiers:productIdentifiers];

Smiley Face

Smiley faces are a very prominent style feature of the raywenderlich.com site! It is very important to have the correct smile signifying the immense amount of happiness and excitement for the coding topic. The end square bracket is used because it represents the largest smile able to be captured using ascii art. A half-hearted smile is represented if an end parenthesis is used, and thus not preferred.

Preferred:

:]

Not Preferred:

:)

Xcode project

The physical files should be kept in sync with the Xcode project files in order to avoid file sprawl. Any Xcode groups created should be reflected by folders in the filesystem. Code should be grouped not only by type, but also by feature for greater clarity.

When possible, always turn on "Treat Warnings as Errors" in the target's Build Settings and enable as many additional warnings as possible. If you need to ignore a specific warning, use Clang's pragma feature.

Other Objective-C Style Guides

If ours doesn't fit your tastes, have a look at some other style guides:

The official raywenderlich.com Objective-C style guide.的更多相关文章

  1. Google C++ Style Guide

    Background C++ is one of the main development languages used by many of Google's open-source project ...

  2. 与你相遇好幸运,The Moe Node.js Code Style Guide

    The Moe Node.js Code Style Guide  By 一个最萌的开发者 @2016.9.21 >>代码是人来阅读的,格式规范的代码是对编程人员最好的礼物 :) > ...

  3. 使用tdcss.js轻松制作自己的style guide

    http://jakobloekke.github.io/tdcss.js/ 在前端开发中,如果能够有一个style guide对于设计来说就显得专业稳定,一致性.在上述链接中,有一个tdcss.js ...

  4. Google C++ Style Guide在C++11普及后的变化

    转 http://www.cnblogs.com/chen3feng/p/5972967.html?from=timeline&isappinstalled=0&lwfrom=user ...

  5. Common Lisp Style Guide - Ariel Networks Labs

    Common Lisp Style Guide - Ariel Networks Labs Common Lisp Style Guide

  6. 一张图总结Google C++编程规范(Google C++ Style Guide)

    Google C++ Style Guide是一份不错的C++编码指南,我制作了一张比較全面的说明图,能够在短时间内高速掌握规范的重点内容.只是规范毕竟是人定的,记得活学活用.看图前别忘了阅读以下三条 ...

  7. Airbnb JavaScript Style Guide

      Airbnb JavaScript Style Guide() { 用更合理的方式写 JavaScript    ES5 的编码规范请查看版本一,版本二. 翻译自 Airbnb JavaScrip ...

  8. PEP 8 – Style Guide for Python Code

    原文:PEP 8 – Style Guide for Python Code PEP:8 题目:Python代码风格指南 作者:Guido van Rossum, www.yszx11.cnBarry ...

  9. Dojo Style Guide

    Contents: General Quick Reference Naming Conventions Specific Naming Conventions Files Variables Lay ...

随机推荐

  1. RESTful测试工具RESTClient

    1.简介 RESTClient是一个用于测试RESTful Web服务的客户端, 是用Java Swing编写的基于Http协议的接口测试工具, 它可以向服务器发送各种Http请求,并显示服务器响应. ...

  2. css 基础 rgba表示法

    color:rgba(); //r表示red 红色 //g表示green 绿色 //b表示blue 蓝色 //a 表示透明度 color:rgb(0,0,0,0) //黑色 color:rgb(255 ...

  3. unittest+ddt_实现数据驱动测试(7)

    我们设计测试用例时,会出现测试步骤一样,只是其中的测试数据有变化的情况,比如测试登录时的账号密码.这个时候,如果我们依然使用一条case一个方法的话,会出现大量的代码冗余,而且效率也会大大降低.此时, ...

  4. 怎样用命令行导入注册表 .reg 文件

    https://stackoverflow.com/questions/49676660/how-to-run-the-reg-file-using-powershell Get-Command re ...

  5. java 封装 总结

    1.前言 老是被问什么是java 封装...很基础的一个问题 ,其实我们一直在写的东西但不知道怎么称呼. 比如 在entity实体类 里面老用到的 getter 和 setter 方法其实就是封装的方 ...

  6. vert.x框架-简单路由使用

    package xue.myVertX; import io.vertx.core.AbstractVerticle; import io.vertx.core.Vertx; import io.ve ...

  7. VC 2010 Express 学生版(中文版)

    Microsoft Visual C++ 2010 Express 学生版 下载传送门(提取码:r7sm) 如何安装 拿到压缩文件后,解压到桌面(别怕,安装完后这个文件夹是可以删除的). 在 &quo ...

  8. SQL高级优化(六)之MySQL索引

    一.索引概述 1. 索引的优点 ​ 为什么要创建索引?这是因为,创建索引可以大大提高系统的查询性能.如果不使用索引,查询时从第一行开始查询.如果使用了索引,所以就可以更加快速的找到希望的数据. 第一. ...

  9. SGU140. Integer Sequences

    https://codeforces.com/problemsets/acmsguru/problem/99999/140 n元同余方程的求解 对于任意二元我们可以替换成kgcd(a,b),不断迭代下 ...

  10. 移动端position:fixed 解决方案

    相信不少人做移动端项目的时候都会遇到position:fixed 的坑. 下面提供一个解决方法,不用引入任何其他的js库,纯css解决. 解决问题的关键就是:fixed元素内部必须嵌套一个positi ...