Swift 语法总结
本页包含内容：
- 语句（Statements）
- 泛型参数（Generic Parameters and Arguments）
- 声明（Declarations）
- 模式（Patterns）
- 特性（Attributes）
- 表达式（Expressions）
- 词法结构（Lexical Structure）
- 类型（Types）
语句
语句语法
statement → expression ; opt
statement → declaration ; opt
statement → loop-statement ; opt
statement → branch-statement ; opt
statement → labeled-statement
statement → control-transfer-statement ; opt
statements → statement statements opt
循环语句语法
loop-statement → for-statement
loop-statement → for-in-statement
loop-statement → while-statement
loop-statement → do-while-statement
For 循环语法
for-statement → for for-init opt ; expression opt ; expression opt code-block
for-statement → for ( for-init opt ; expression opt ; expression opt ) code-block
for-init → variable-declaration | expression-list
For-In 循环语法
for-in-statement → for pattern in expression code-block
While 循环语法
while-statement → while while-condition code-block
while-condition → expression | declaration
Do-While 循环语法
do-while-statement → do code-block while while-condition
分支语句语法
branch-statement → if-statement
branch-statement → switch-statement
If 语句语法
if-statement → if if-condition code-block else-clause opt
if-condition → expression | declaration
else-clause → else code-block | else if-statement
Switch 语句语法
switch-statement → switch expression { switch-cases opt }
switch-cases → switch-case switch-cases opt
switch-case → case-label statements | default-label statements
switch-case → case-label ; | default-label ;
case-label → case case-item-list :
case-item-list → pattern guard-clause opt | pattern guard-clause opt , case-item-list
default-label → default :
guard-clause → where guard-expression
guard-expression → expression
带标签的语句语法
labeled-statement → statement-label loop-statement | statement-label switch-statement
statement-label → label-name :
label-name → identifier
控制传递语句语法
control-transfer-statement → break-statement
control-transfer-statement → continue-statement
control-transfer-statement → fallthrough-statement
control-transfer-statement → return-statement
Break 语句语法
break-statement → break label-name opt
Continue 语句语法
continue-statement → continue label-name opt
Fallthrough 语句语法
fallthrough-statement → fallthrough
Return 语句语法
return-statement → return expression opt
泛型参数
泛型形参子句语法
generic-parameter-clause → < generic-parameter-list requirement-clause opt >
generic-parameter-list → generic-parameter | generic-parameter , generic-parameter-list
generic-parameter → type-name
generic-parameter → type-name : type-identifier
generic-parameter → type-name : protocol-composition-type
requirement-clause → where requirement-list
requirement-list → requirement | requirement , requirement-list
requirement → conformance-requirement | same-type-requirement
conformance-requirement → type-identifier : type-identifier
conformance-requirement → type-identifier : protocol-composition-type
same-type-requirement → type-identifier == type-identifier
泛型实参子句语法
generic-argument-clause → < generic-argument-list >
generic-argument-list → generic-argument | generic-argument , generic-argument-list
generic-argument → type
声明 (Declarations)
声明语法
declaration → import-declaration
declaration → constant-declaration
declaration → variable-declaration
declaration → typealias-declaration
declaration → function-declaration
declaration → enum-declaration
declaration → struct-declaration
declaration → class-declaration
declaration → protocol-declaration
declaration → initializer-declaration
declaration → deinitializer-declaration
declaration → extension-declaration
declaration → subscript-declaration
declaration → operator-declaration
declarations → declaration declarations opt
declaration-specifiers → declaration-specifier declaration-specifiers opt
declaration-specifier → class | mutating | nonmutating | override | static | unowned | unowned(safe) | unowned(unsafe) | weak
顶级声明语法
top-level-declaration → statements opt
代码块语法
code-block → { statements opt }
Import 声明语法
import-declaration → attributes opt import import-kind opt import-path
import-kind → typealias | struct | class | enum | protocol | var | func
import-path → import-path-identifier | import-path-identifier . import-path
import-path-identifier → identifier | operator
常数声明语法
constant-declaration → attributes opt declaration-specifiers opt let pattern-initializer-list
pattern-initializer-list → pattern-initializer | pattern-initializer , pattern-initializer-list
pattern-initializer → pattern initializer opt
initializer → = expression
变量声明语法
variable-declaration → variable-declaration-head pattern-initializer-list
variable-declaration → variable-declaration-head variable-name type-annotation code-block
variable-declaration → variable-declaration-head variable-name type-annotation getter-setter-block
variable-declaration → variable-declaration-head variable-name type-annotation getter-setter-keyword-block
variable-declaration → variable-declaration-head variable-name type-annotation initializer opt willSet-didSet-block
variable-declaration-head → attributes opt declaration-specifiers opt var
variable-name → identifier
getter-setter-block → { getter-clause setter-clause opt }
getter-setter-block → { setter-clause getter-clause }
getter-clause → attributes opt get code-block
setter-clause → attributes opt set setter-name opt code-block
setter-name → ( identifier )
getter-setter-keyword-block → { getter-keyword-clause setter-keyword-clause opt }
getter-setter-keyword-block → { setter-keyword-clause getter-keyword-clause }
getter-keyword-clause → attributes opt get
setter-keyword-clause → attributes opt set
willSet-didSet-block → { willSet-clause didSet-clause opt }
willSet-didSet-block → { didSet-clause willSet-clause }
willSet-clause → attributes opt willSet setter-name opt code-block
didSet-clause → attributes opt didSet setter-name opt code-block
类型别名声明语法
typealias-declaration → typealias-head typealias-assignment
typealias-head → typealias typealias-name
typealias-name → identifier
typealias-assignment → = type
函数声明语法
function-declaration → function-head function-name generic-parameter-clause opt function-signature function-body
function-head → attributes opt declaration-specifiers opt func
function-name → identifier | operator
function-signature → parameter-clauses function-result opt
function-result → -> attributes opt type
function-body → code-block
parameter-clauses → parameter-clause parameter-clauses opt
parameter-clause → ( ) | ( parameter-list ... opt )
parameter-list → parameter | parameter , parameter-list
parameter → inout opt let opt # opt parameter-name local-parameter-name opt type-annotation default-argument-clause opt
parameter → inout opt var # opt parameter-name local-parameter-name opt type-annotation default-argument-clause opt
parameter → attributes opt type
parameter-name → identifier | _
local-parameter-name → identifier | _
default-argument-clause → = expression
枚举声明语法
enum-declaration → attributes opt union-style-enum | attributes opt raw-value-style-enum
union-style-enum → enum-name generic-parameter-clause opt { union-style-enum-members opt }
union-style-enum-members → union-style-enum-member union-style-enum-members opt
union-style-enum-member → declaration | union-style-enum-case-clause
union-style-enum-case-clause → attributes opt case union-style-enum-case-list
union-style-enum-case-list → union-style-enum-case | union-style-enum-case , union-style-enum-case-list
union-style-enum-case → enum-case-name tuple-type opt
enum-name → identifier
enum-case-name → identifier
raw-value-style-enum → enum-name generic-parameter-clause opt : type-identifier { raw-value-style-enum-members opt }
raw-value-style-enum-members → raw-value-style-enum-member raw-value-style-enum-members opt
raw-value-style-enum-member → declaration | raw-value-style-enum-case-clause
raw-value-style-enum-case-clause → attributes opt case raw-value-style-enum-case-list
raw-value-style-enum-case-list → raw-value-style-enum-case | raw-value-style-enum-case , raw-value-style-enum-case-list
raw-value-style-enum-case → enum-case-name raw-value-assignment opt
raw-value-assignment → = literal
结构体声明语法
struct-declaration → attributes opt struct struct-name generic-parameter-clause opt type-inheritance-clause opt struct-body
struct-name → identifier
struct-body → { declarations opt }
类声明语法
class-declaration → attributes opt class class-name generic-parameter-clause opt type-inheritance-clause opt class-body
class-name → identifier
class-body → { declarations opt }
协议声明语法
protocol-declaration → attributes opt protocol protocol-name type-inheritance-clause opt protocol-body
protocol-name → identifier
protocol-body → { protocol-member-declarations opt }
protocol-member-declaration → protocol-property-declaration
protocol-member-declaration → protocol-method-declaration
protocol-member-declaration → protocol-initializer-declaration
protocol-member-declaration → protocol-subscript-declaration
protocol-member-declaration → protocol-associated-type-declaration
protocol-member-declarations → protocol-member-declaration protocol-member-declarations opt
协议属性声明语法
protocol-property-declaration → variable-declaration-head variable-name type-annotation getter-setter-keyword-block
协议方法声明语法
protocol-method-declaration → function-head function-name generic-parameter-clause opt function-signature
协议构造函数声明语法
protocol-initializer-declaration → initializer-head generic-parameter-clause opt parameter-clause
协议附属脚本声明语法
protocol-subscript-declaration → subscript-head subscript-result getter-setter-keyword-block
协议关联类型声明语法
protocol-associated-type-declaration → typealias-head type-inheritance-clause opt typealias-assignment opt
构造函数声明语法
initializer-declaration → initializer-head generic-parameter-clause opt parameter-clause initializer-body
initializer-head → attributes opt convenience opt init
initializer-body → code-block
析构函数声明语法
deinitializer-declaration → attributes opt deinit code-block
扩展声明语法
extension-declaration → extension type-identifier type-inheritance-clause opt extension-body
extension-body → { declarations opt }
附属脚本声明语法
subscript-declaration → subscript-head subscript-result code-block
subscript-declaration → subscript-head subscript-result getter-setter-block
subscript-declaration → subscript-head subscript-result getter-setter-keyword-block
subscript-head → attributes opt subscript parameter-clause
subscript-result → -> attributes opt type
运算符声明语法
operator-declaration → prefix-operator-declaration | postfix-operator-declaration | infix-operator-declaration
prefix-operator-declaration → operator prefix operator { }
postfix-operator-declaration → operator postfix operator { }
infix-operator-declaration → operator infix operator { infix-operator-attributes opt }
infix-operator-attributes → precedence-clause opt associativity-clause opt
precedence-clause → precedence precedence-level
precedence-level → Digit 0 through 255
associativity-clause → associativity associativity
associativity → left | right | none
模式
模式语法
pattern → wildcard-pattern type-annotation opt
pattern → identifier-pattern type-annotation opt
pattern → value-binding-pattern
pattern → tuple-pattern type-annotation opt
pattern → enum-case-pattern
pattern → type-casting-pattern
pattern → expression-pattern
通配符模式语法
wildcard-pattern → _
标识符模式语法
identifier-pattern → identifier
元组模式语法
tuple-pattern → ( tuple-pattern-element-list opt )
tuple-pattern-element-list → tuple-pattern-element | tuple-pattern-element , tuple-pattern-element-list
tuple-pattern-element → pattern
枚举用例模式语法
enum-case-pattern → type-identifier opt . enum-case-name tuple-pattern opt
类型转换模式语法
type-casting-pattern → is-pattern | as-pattern
is-pattern → is type
as-pattern → pattern as type
表达式模式语法
expression-pattern → expression
特性
特性语法
attribute → @ attribute-name attribute-argument-clause opt
attribute-name → identifier
attribute-argument-clause → ( balanced-tokens opt )
attributes → attribute attributes opt
balanced-tokens → balanced-token balanced-tokens opt
balanced-token → ( balanced-tokens opt )
balanced-token → [ balanced-tokens opt ]
balanced-token → { balanced-tokens opt }
balanced-token → Any identifier, keyword, literal, or operator
balanced-token → Any punctuation except (, ), [, ], {, or }
表达式
表达式语法
expression → prefix-expression binary-expressions opt
expression-list → expression | expression , expression-list
前缀表达式语法
prefix-expression → prefix-operator opt postfix-expression
prefix-expression → in-out-expression
in-out-expression → & identifier
二进制表达式语法
binary-expression → binary-operator prefix-expression
binary-expression → assignment-operator prefix-expression
binary-expression → conditional-operator prefix-expression
binary-expression → type-casting-operator
binary-expressions → binary-expression binary-expressions opt
赋值运算符语法
assignment-operator → =
条件运算符语法
conditional-operator → ? expression :
主表达式语法
primary-expression → identifier generic-argument-clause opt
primary-expression → literal-expression
primary-expression → self-expression
primary-expression → superclass-expression
primary-expression → closure-expression
primary-expression → parenthesized-expression
primary-expression → implicit-member-expression
primary-expression → wildcard-expression
字面量表达式语法
literal-expression → literal
literal-expression → array-literal | dictionary-literal
literal-expression → __FILE__ | __LINE__ | __COLUMN__ | __FUNCTION__
array-literal → [ array-literal-items opt ]
array-literal-items → array-literal-item , opt | array-literal-item , array-literal-items
array-literal-item → expression
dictionary-literal → [ dictionary-literal-items ] | [ : ]
dictionary-literal-items → dictionary-literal-item , opt | dictionary-literal-item , dictionary-literal-items
dictionary-literal-item → expression : expression
Self 表达式语法
self-expression → self
self-expression → self . identifier
self-expression → self [ expression ]
self-expression → self . init
超类表达式语法
superclass-expression → superclass-method-expression | superclass-subscript-expression | superclass-initializer-expression
superclass-method-expression → super . identifier
superclass-subscript-expression → super [ expression ]
superclass-initializer-expression → super . init
闭包表达式语法
closure-expression → { closure-signature opt statements }
closure-signature → parameter-clause function-result opt in
closure-signature → identifier-list function-result opt in
closure-signature → capture-list parameter-clause function-result opt in
closure-signature → capture-list identifier-list function-result opt in
closure-signature → capture-list in
capture-list → [ capture-specifier expression ]
capture-specifier → weak | unowned | unowned(safe) | unowned(unsafe)
隐式成员表达式语法
implicit-member-expression → . identifier
带圆括号的表达式语法
parenthesized-expression → ( expression-element-list opt )
expression-element-list → expression-element | expression-element , expression-element-list
expression-element → expression | identifier : expression
通配符表达式语法
wildcard-expression → _
后缀表达式语法
postfix-expression → primary-expression
postfix-expression → postfix-expression postfix-operator
postfix-expression → function-call-expression
postfix-expression → initializer-expression
postfix-expression → explicit-member-expression
postfix-expression → postfix-self-expression
postfix-expression → dynamic-type-expression
postfix-expression → subscript-expression
postfix-expression → forced-value-expression
postfix-expression → optional-chaining-expression
函数调用表达式语法
function-call-expression → postfix-expression parenthesized-expression
function-call-expression → postfix-expression parenthesized-expression opt trailing-closure
trailing-closure → closure-expression
初始化表达式语法
initializer-expression → postfix-expression . init
显式成员表达式语法
explicit-member-expression → postfix-expression . decimal-digit
explicit-member-expression → postfix-expression . identifier generic-argument-clause opt
Self 表达式语法
postfix-self-expression → postfix-expression . self
动态类型表达式语法
dynamic-type-expression → postfix-expression . dynamicType
附属脚本表达式语法
subscript-expression → postfix-expression [ expression-list ]
Forced-value 表达式语法
forced-value-expression → postfix-expression !
可选链表达式语法
optional-chaining-expression → postfix-expression ?
词法结构
标识符语法
identifier → identifier-head identifier-characters opt
identifier → ` identifier-head identifier-characters opt `
identifier → implicit-parameter-name
identifier-list → identifier | identifier , identifier-list
identifier-head → Upper- or lowercase letter A through Z
identifier-head → U+00A8, U+00AA, U+00AD, U+00AF, U+00B2–U+00B5, or U+00B7–U+00BA
identifier-head → U+00BC–U+00BE, U+00C0–U+00D6, U+00D8–U+00F6, or U+00F8–U+00FF
identifier-head → U+0100–U+02FF, U+0370–U+167F, U+1681–U+180D, or U+180F–U+1DBF
identifier-head → U+1E00–U+1FFF
identifier-head → U+200B–U+200D, U+202A–U+202E, U+203F–U+2040, U+2054, or U+2060–U+206F
identifier-head → U+2070–U+20CF, U+2100–U+218F, U+2460–U+24FF, or U+2776–U+2793
identifier-head → U+2C00–U+2DFF or U+2E80–U+2FFF
identifier-head → U+3004–U+3007, U+3021–U+302F, U+3031–U+303F, or U+3040–U+D7FF
identifier-head → U+F900–U+FD3D, U+FD40–U+FDCF, U+FDF0–U+FE1F, or U+FE30–U+FE44
identifier-head → U+FE47–U+FFFD
identifier-head → U+10000–U+1FFFD, U+20000–U+2FFFD, U+30000–U+3FFFD, or U+40000–U+4FFFD
identifier-head → U+50000–U+5FFFD, U+60000–U+6FFFD, U+70000–U+7FFFD, or U+80000–U+8FFFD
identifier-head → U+90000–U+9FFFD, U+A0000–U+AFFFD, U+B0000–U+BFFFD, or U+C0000–U+CFFFD
identifier-head → U+D0000–U+DFFFD or U+E0000–U+EFFFD
identifier-character → Digit 0 through 9
identifier-character → U+0300–U+036F, U+1DC0–U+1DFF, U+20D0–U+20FF, or U+FE20–U+FE2F
identifier-character → identifier-head
identifier-characters → identifier-character identifier-characters opt
implicit-parameter-name → $ decimal-digits
字面量语法
literal → integer-literal | floating-point-literal | string-literal
整形字面量语法
integer-literal → binary-literal
integer-literal → octal-literal
integer-literal → decimal-literal
integer-literal → hexadecimal-literal
binary-literal → 0b binary-digit binary-literal-characters opt
binary-digit → Digit 0 or 1
binary-literal-character → binary-digit | _
binary-literal-characters → binary-literal-character binary-literal-characters opt
octal-literal → 0o octal-digit octal-literal-characters opt
octal-digit → Digit 0 through 7
octal-literal-character → octal-digit | _
octal-literal-characters → octal-literal-character octal-literal-characters opt
decimal-literal → decimal-digit decimal-literal-characters opt
decimal-digit → Digit 0 through 9
decimal-digits → decimal-digit decimal-digits opt
decimal-literal-character → decimal-digit | _
decimal-literal-characters → decimal-literal-character decimal-literal-characters opt
hexadecimal-literal → 0x hexadecimal-digit hexadecimal-literal-characters opt
hexadecimal-digit → Digit 0 through 9, a through f, or A through F
hexadecimal-literal-character → hexadecimal-digit | _
hexadecimal-literal-characters → hexadecimal-literal-character hexadecimal-literal-characters opt
浮点型字面量语法
floating-point-literal → decimal-literal decimal-fraction opt decimal-exponent opt
floating-point-literal → hexadecimal-literal hexadecimal-fraction opt hexadecimal-exponent
decimal-fraction → . decimal-literal
decimal-exponent → floating-point-e sign opt decimal-literal
hexadecimal-fraction → . hexadecimal-literal opt
hexadecimal-exponent → floating-point-p sign opt hexadecimal-literal
floating-point-e → e | E
floating-point-p → p | P
sign → + | -
字符型字面量语法
string-literal → " quoted-text "
quoted-text → quoted-text-item quoted-text opt
quoted-text-item → escaped-character
quoted-text-item → ( expression )
quoted-text-item → Any Unicode extended grapheme cluster except ", \, U+000A, or U+000D
escaped-character → \0 | \ | \t | \n | \r | \" | \'
escaped-character → \x hexadecimal-digit hexadecimal-digit
escaped-character → \u hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
escaped-character → \U hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
运算符语法语法
operator → operator-character operator opt
operator-character → / | = | - | + | ! | * | % | < | > | & | | | ^ | ~ | .
binary-operator → operator
prefix-operator → operator
postfix-operator → operator
类型
类型语法
type → array-type | function-type | type-identifier | tuple-type | optional-type | implicitly-unwrapped-optional-type | protocol-composition-type | metatype-type
类型标注语法
type-annotation → : attributes opt type
类型标识语法
type-identifier → type-name generic-argument-clause opt | type-name generic-argument-clause opt . type-identifier
type-name → identifier
元组类型语法
tuple-type → ( tuple-type-body opt )
tuple-type-body → tuple-type-element-list ... opt
tuple-type-element-list → tuple-type-element | tuple-type-element , tuple-type-element-list
tuple-type-element → attributes opt inout opt type | inout opt element-name type-annotation
element-name → identifier
数组类型语法
array-type → type [ ] | array-type [ ]
可选类型语法
optional-type → type ?
隐式解析可选类型语法
implicitly-unwrapped-optional-type → type !
协议合成类型语法
protocol-composition-type → protocol < protocol-identifier-list opt >
protocol-identifier-list → protocol-identifier | protocol-identifier , protocol-identifier-list
protocol-identifier → type-identifier
类型继承子句语法
type-inheritance-clause → : type-inheritance-list
type-inheritance-list → type-identifier | type-identifier , type-inheritance-list