@ -46,7 +46,7 @@
< div class = "book" data-level = "3.5" data-basepath = ".." data-revision = "1402402017737 " >
< div class = "book" data-level = "3.5" data-basepath = ".." data-revision = "1402440614492 " >
< div class = "book-header" >
<!-- Actions Left -->
< a href = "#" class = "btn pull-left toggle-summary" aria-label = "Toggle summary" > < i class = "fa fa-align-justify" > < / i > < / a >
@ -587,7 +587,7 @@
< div class = "page-inner" >
< section class = "normal" id = "section-gitbook_83 " >
< section class = "normal" id = "section-gitbook_85 " >
< h1 id = "-" > 语句< / h1 >
< hr >
@ -632,7 +632,7 @@
< li > < p > 计算< em > increment< / em > 表达式， < / p >
< / li >
< / ol >
< p > 定义在< em > initialzation< / em > 中的变量仅在< code > for< / code > 语句的作用域以内有效。< em > condition< / em > 表达式的值的类型必须符合 < code > LogicValue< / code > 协议。< / p >
< p > 定义在< em > initialzation< / em > 中的变量仅在< code > for< / code > 语句的作用域以内有效。< em > condition< / em > 表达式的值的类型必须遵循 < code > LogicValue< / code > 协议。< / p >
< blockquote >
< p > GRAMMAR OF A FOR STATEMENT< / p >
< p > < em > for-statement< / em > → < strong > for< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Statements.html#//apple_ref/swift/grammar/for-init" target = "_blank" > < em > for-init< / em > < / a > < em > opt< / em > < strong > ;< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Expressions.html#//apple_ref/swift/grammar/expression" target = "_blank" > < em > expression< / em > < / a > < em > opt< / em > < strong > ;< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Expressions.html#//apple_ref/swift/grammar/expression" target = "_blank" > < em > expression< / em > < / a > < em > opt< / em > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/code-block" target = "_blank" > < em > code-block< / em > < / a > < / p >
@ -640,13 +640,13 @@
< p > < em > for-statement< / em > → < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/variable-declaration" target = "_blank" > < em > variable-declaration< / em > < / a > | < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Expressions.html#//apple_ref/swift/grammar/expression-list" target = "_blank" > < em > expression-list< / em > < / a > < / p >
< / blockquote >
< h3 id = "for-in-" > For-In 语句< / h3 >
< p > < code > for-in< / code > 语句允许在重复执行代码块的同时，迭代集合(或符合 < code > Sequence< / code > 协议的任意类型)中的每一项。< / p >
< p > < code > for-in< / code > 语句允许在重复执行代码块的同时，迭代集合(或遵循 < code > Sequence< / code > 协议的任意类型)中的每一项。< / p >
< p > < code > for-in< / code > 语句的形式如下：< / p >
< pre > < code class = "lang-swift" > for `item` in `collection` {
`statements`
}
< / code > < / pre >
< p > < code > for-in< / code > 语句在循环开始前会调用< em > collection< / em > 表达式的< code > generate< / code > 方法来获取一个生成器类型（这是一个符合 < code > Generator< / code > 协议的类型）的值。接下来循环开始，调用< em > collection< / em > 表达式的< code > next< / code > 方法。如果其返回值不是< code > None< / code > ，它将会被赋给< em > item< / em > ，然后执行< em > statements< / em > ，执行完毕后回到循环开始处；否则，将不会赋值给< em > item< / em > 也不会执行< em > statements< / em > ， < code > for-in< / code > 至此执行完毕。< / p >
< p > < code > for-in< / code > 语句在循环开始前会调用< em > collection< / em > 表达式的< code > generate< / code > 方法来获取一个生成器类型（这是一个遵循 < code > Generator< / code > 协议的类型）的值。接下来循环开始，调用< em > collection< / em > 表达式的< code > next< / code > 方法。如果其返回值不是< code > None< / code > ，它将会被赋给< em > item< / em > ，然后执行< em > statements< / em > ，执行完毕后回到循环开始处；否则，将不会赋值给< em > item< / em > 也不会执行< em > statements< / em > ， < code > for-in< / code > 至此执行完毕。< / p >
< blockquote >
< p > GRAMMAR OF A FOR-IN STATEMENT< / p >
< p > < em > for-in-statement< / em > → < strong > for< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/pattern" target = "_blank" > < em > pattern< / em > < / a > < strong > in< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Expressions.html#//apple_ref/swift/grammar/expression" target = "_blank" > < em > expression< / em > < / a > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/code-block" target = "_blank" > < em > code-block< / em > < / a > < / p >
@ -667,7 +667,7 @@
< / li >
< / ol >
< p > 由于< em > condition< / em > 的值在< em > statements< / em > 执行前就已计算出，因此< code > while< / code > 语句中的< em > statements< / em > 可能会被执行若干次，也可能不会被执行。< / p >
< p > < em > condition< / em > 表达式的值的类型必须符合 < code > LogicValue< / code > 协议。同时，< em > condition< / em > 表达式也可以使用可选绑定，请参考< a href = "" > 可选绑定< code > 待添加链接< / code > < / a > 。< / p >
< p > < em > condition< / em > 表达式的值的类型必须遵循 < code > LogicValue< / code > 协议。同时，< em > condition< / em > 表达式也可以使用可选绑定，请参考< a href = "" > 可选绑定< code > 待添加链接< / code > < / a > 。< / p >
< blockquote >
< p > GRAMMAR OF A WHILE STATEMENT< / p >
< p > < em > while-statement< / em > → < strong > while< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Statements.html#//apple_ref/swift/grammar/while-condition" target = "_blank" > < em > while-condition< / em > < / a > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/code-block" target = "_blank" > < em > code-block< / em > < / a > < / p >
@ -689,7 +689,7 @@
< / li >
< / ol >
< p > 由于< em > condition< / em > 表达式的值是在< em > statements< / em > 表达式执行后才计算出，因此< em > do-while< / em > 语句中的< em > statements< / em > 至少会被执行一次。< / p >
< p > < em > condition< / em > 表达式的值的类型必须符合 < code > LogicValue< / code > 协议。同时，< em > condition< / em > 表达式也可以使用可选绑定，请参考< a href = "" > 可选绑定< code > 待添加链接< / code > < / a > 。< / p >
< p > < em > condition< / em > 表达式的值的类型必须遵循 < code > LogicValue< / code > 协议。同时，< em > condition< / em > 表达式也可以使用可选绑定，请参考< a href = "" > 可选绑定< code > 待添加链接< / code > < / a > 。< / p >
< blockquote >
< p > GRAMMAR OF A DO-WHILE STATEMENT< / p >
< p > < em > do-while-statement< / em > → < strong > do< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/code-block" target = "_blank" > < em > code-block< / em > < / a > < strong > while< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Statements.html#//apple_ref/swift/grammar/while-condition" target = "_blank" > < em > while-condition< / em > < / a > < / p >
@ -727,7 +727,7 @@ else {
`statements to execute if both conditions are false`
}
< / code > < / pre >
< p > < code > if< / code > 语句中条件的值的类型必须符合 < code > LogicValue< / code > 协议。同时，条件也可以使用可选绑定，请参考< a href = "" > 可选绑定< code > 待添加链接< / code > < / a > 。< / p >
< p > < code > if< / code > 语句中条件的值的类型必须遵循 < code > LogicValue< / code > 协议。同时，条件也可以使用可选绑定，请参考< a href = "" > 可选绑定< code > 待添加链接< / code > < / a > 。< / p >
< blockquote >
< p > GRAMMAR OF AN IF STATEMENT< / p >
< p > < em > if-statement< / em > → < strong > if< / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Statements.html#//apple_ref/swift/grammar/if-condition" target = "_blank" > < em > if-condition< / em > < / a > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Declarations.html#//apple_ref/swift/grammar/code-block" target = "_blank" > < em > code-block< / em > < / a > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Statements.html#//apple_ref/swift/grammar/else-clause" target = "_blank" > < em > else-clause< / em > < / a > < em > opt< / em > < / p >
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