You most probably was working on an open source project, and must have noticed projects are usually organized and consistent 🧐, this is due to following a code style, and you must have noticed that some projects are messy, ugly and inconsistent 🤮.
There are different Swift Code Styles, one by Apple, Google, Ray Wenderlich, Linkedin and AirBNB, and others, preferring a code style over another is subjective, I recommend inspecting different styles and adopt one according to the project needs.
Developers spend time reading code, more than writing new code 😌, this alone justifies having a consistent clean coding style, this is an investment you do for yourself as a developer, and for your colleagues 😇, regular indentation, proper spelling, .. etc does not make your task take longer, in the contrary, it saves you big load of time in the future, and improves readability and maintainability.
There is an official API Design guidelines, it covers naming conventions, but is not comprehensive enough.
Another guideline can be found here, by Nikita Lazarev-Zubov, it looks like she has preservations on some guidelines too, I highly recommend going through these guidelines and inspecting yourself.
A reserved word is a word that cannot be used as an identifier, this is a syntactic definition, as mentioned before in Swift Lexical Structure, all lists below are written alphabetically.
Keywords used in declarations:
Reserved Word
Details
associatedtype
Associated types are a powerful way of making protocols generic, it gives a placeholder name to a type that’s used as part of the protocol.
class
One of swift’s general purpose, flexible constructs also see struct
deinit
A method that gets automatically called when an object is freed up from memory by ARC.
enum
Enums let’s you define a custom kind of value in Swift, with predefined possible values.
extension
Extensions add new functionality to an existing class, structure, enumeration, or protocol type.
fileprivate
One of swift’s access modifiers.
func
Used for creating functions.
import
A declaration used for importing modules and submodules
init
as per swift documentation, “Initialization is the process of preparing an instance of a class, structure, or enumeration for use.”
inout
inout allows parameters to be changed outside of the function scope.
internal
One of swift’s access modifiers.
let
A keyword used for declaring a constant
open
One of swift’s access modifiers.
operator
A special symbol/ phrase that you use to check, change, or combine values.
private
One of swift’s access modifiers.
precedencegroup
defining precedence groups to use for our custom operators.
protocol
as per swift’s official documentation “A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.”
public
One of swift’s access modifiers.
rethrows
rethrows keyword is used with function that accepts a throwing function as a parameter.
static
defines a static scope.
struct
complex value-types.
subscript
Subscripts allow you to write shortcuts to elements from collections, Sequences in classes, structures and enumerations.
typealias
Defines an alias for an existing type.
var
A keyword used for declaring a variable.
Keywords used in statements:
Reserved Word
Details
break
One of the control transfer statements, ends execution of a loop, an if statement, or a switch statement.
case
Used for pattern testing.
catch
Used for handling any potential errors caused by a function that throws.
continue
One of the control transfer statements, ends execution of the current iteration of a loop statement but does not stop execution of the loop statement.
default
Used for default cases in switch.
defer
Used for making a block to execute just before a function exits.
do
Used for creating do blocks, for example (do-while, do-catch)
else
Used for executing a block when a condition is not satisfied.
fallthrough
One of the control transfer statements
for
Used for iterating over a sequence.
guard
Used in control transfer statement and optional unwrapping.
if
Used for condition evaluation.
in
In is a keyword defined in the Swift closure syntax as a separator between the function type and the function body in a closure, and used in checking if an object is in a sequence.
repeat
A control flow statement, similar to while loop
return
One of the control transfer statements
throw
Used for throwing an error in a function that throws.
switch
A switch statement considers a value and compares it against several possible matching patterns.
where
Used to filter out values, in statements like switch, for, protocol extension, first, contains, initializers.
while
A control flow statement, it performs a set of statements until a condition becomes false
Keywords used in expressions and types:
Reserved Word
Details
Any
Any can represent an instance of any type at all, including function types.
as
Used for type casting.
catch
Used in error handling, when an error is thrown, it’s matched against the catch clauses.
false
A literal used to express booleans.
is
Used to check whether an object is of a certain class type
nil
A valueless state that could be assigned to optionals.
rethrows
allows forwarding a thrown error by a given function parameter
self
“self” refers to the current object within a class or struct.
Self
Refers to a type – usually the current type in the current context.
super
super is used to call up to your superclass.
throw
Used for throwing an error in a function that throws.
throws
To mark a function throwing.
true
A literal used to express booleans.
try
The try keyword is used to indicate that a method can throw an error. To catch and handle an error, the throwing method call needs to be wrapped in a do-catch statement.
Keywords used in patterns:
Reserved Word
_
.
Keywords that begin with a number sign (#), literals expressions:
Reserved Word
Details
#available
Used to determine the availability of APIs at runtime
#colorLiteral
Used to make the XCode IDE to display a color swatch 🟥
#column
column number of the line where it is being run.
#dsohandle
–
#elseif
Literal conditional statement
#else
Literal else statement.
#endif
Literal marker for closing an a literal if statement
#error
Creates a red compiler error & prevents code from compiling
#fileID
Generates concise file string in all language modes.
#fileLiteral
Used to make the XCode IDE link to a local file.
#filePath
Outputs the file path of in which code is being run.
#file
Outputs the name of the file in which code is being run.
#function
Outputs the name of the function where code belongs.
#if
Literal if statement.
#imageLiteral
Used to make the XCode IDE to display an image.
#keyPath
–
#line
line number where it is being run.
#selector
–
#sourceLocation
–
#warning
will cause Xcode to display a warning with the given message.
Keywords reserved in particular contexts:
Reserved Word
Details
associativity
defines how operators of the same precedence are grouped together.
convenience
Convenience modifier placed before the init keyword.
didSet
A property observer
dynamic
A declaration modifier used to make use of Objective-C’s dynamism.
final
One of Swift’s access modifiers.
get
Used when getting a computed property.
indirect
Used for recursive Enums
infix
Used when creating custom operators.
lazy
Used for just-in-time calculation.
left
Used to specify the associativity of a custom operator
mutating
Functions marked as mutating can change any property within its enclosing value
none
Used to specify the associativity of a custom operator
nonmutating
–
optional
–
override
Used for overriding child classes.
postfix
Used in creating custom functions, it’s mathematical notation in which operators follow operands.
precedence
Operator precedence is a set of rules that determine which operator is executed before another.
prefix
Used in creating custom functions, it’s mathematical notation in which operators follow operands.
Protocol
A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.
required
Required keyword means that inheriting classes must provide an implementation of the method.
right
Used to specify the associativity of a custom operator
set
Used when getting a computed property.
some
denotes an opaque type.
Type
A metatype type refers to the type of any type, including class types, structure types, enumeration types, and protocol types.
unowned
A reference type, used for memory management.
weak
A reference type, used for memory management.
willSet
A property observer
Outside the context in which they appear in the grammar, they can be used as identifiers.
The following tokens are reserved as punctuation and can’t be used as custom operators:
Swift lexical structure, consists of valid tokens (lowest-level building blocks) that form the structure of any swift program, these tokens describe the rest of whole swift language…
A token consists of an identifier, keyword, punctuation, literal, or operator.
1) Identifiers: An example of an identifier is a variable name, for example here “pet” is an identifier.
let pet = "Happy Dinosaur 🦖";
Identifiers support unicode characters, you can name you variable in you native language, and as in other programming languages, you cannot use keywords as identifiers, this is still possible if you surrounding a keyword with back-ticks,
var `var` = "var"
examples of unicode identifiers are
var _latitude = 32.0; var アップル = "apple";
2) Keywords: The list of basic keywords in swift are listed below, see (Swift Reserved Keywords) for comprehensive list and details.
class
deinit
enum
extension
func
import
init
let
protocol
static
struct
subscript
typealias
var
break
continue
default
do
else
fallthrough
if
in
for
return
switch
where
while
as
dynamicType
is
new
super
self
Self
Type
__COLUMN__
__FILE__
__FUNCTION__
__LINE__
associativity
didSet
get
infix
inout
left
mutating
none
nonmutating
override
precedence
prefix
right
set
unowned
unowned(safe)
unowned(unsafe)
weak
willSet
3) Literals: literals fall into 3 categories, integer, floating point, and string literals
Integer Literals var a = 10 //Binary var b = 00010100b //Hexadecimal var c = 14x //Octal var d = 24o
leading zeros will be ignored by the compiler, and the use of underscores is possible to increase readability.
var a = 100_000_000
Floating Point Literals //Simple floating point number var a = 10.7 //Exponent floating point number var b = 10.6e2 var c = 10.1e-2 //Exponent floating point number
//Hexa decimal exponent var d = 0xAp2 //Hexa decimal exponent var d = 0xAp-2
String Literals
String literals are characters are enclosed within double quotes. Strings can contain escape sequences to represent characters like qoutes. Example for string literal is shown below.
var a = “test” var a = “Hello\nWorld”
\0 Null Character \ Backslash \t Horizontal Tab \n New line \r Carriage Return \” Double Quote \’ Single Quote
4) Operators: There are different operators supported in swift which includes + : Addition – : Subtraction * : Multiplication / : Division % : Remainder ^ : Exponent & : Bitwise And && : Logical And | : Bitwise Or || : Logical Or ++ : Increment Operator – : Minus ~ : Bitwise Not < : Less Than > : Greater Than … etc.
Keep in mind, as in Swift’s official documentation, this is a list of reserved punctuation and can’t be used as custom operators: “(, ), {, }, [, ], ., ,, :, ;, =, @, #, & (as a prefix operator), ->, `, ?, and ! (as a postfix operator)”
Swift Whitespace: White spaces are used to separate tokens and to distinguish prefixes, otherwise it’s normally omitted by the compiler.
Swift Comments: these are statements that are ignored by the compiler, and meant for documentation purposes of our code, they could be either one-line or multi-line.
// This is a single line comment /* Multi line (block) comment - can have more than one line! */
