翻译：StanZhai

校对：xielingwang

语法总结

本页包含内容：

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

值绑定模式语法 value-binding-pattern → var pattern | let pattern

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 :

类型转换运算符语法 type-casting-operator → is type | as ? opt type

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

函数类型语法 function-type → type -> type

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

元类型语法 metatype-type → type . Type | type . Protocol

类型继承子句语法 type-inheritance-clause → : type-inheritance-list type-inheritance-list → type-identifier | type-identifier , type-inheritance-list