5.1.块.md

5.1.块

Haxe中的一个块由一个开口的 花括号 { 开始，以一个闭口的花括号 }结束。一个块可以包含一些表达式，每个使用分号结束。通常的语法是：

A block in Haxe starts with an opening curly brace { and ends with a closing curly brace }. A block may contain several expressions, each of which is followed by a semicolon ;. The general syntax is thus:

{ 
    expr1;
    expr2;
    ... 
    exprN;
} 

被块表达式扩展的值和类型等于最后一个子表达式的值和类型。

The value and by extension the type of a block-expression is equal to the value and the type of the last sub-expression.

块可以包含局部变量，通过 var表达式（第5.10节）声明，同样，局部函数通过 function 表达式（第5.11节）声明。它们在块和子块中中是可用的，但是不能在块的范围之外使用。同样，只有在被声明之后才可以使用。下面的例子使用 var，但是同样的规则也适用于 function 的使用：

Blocks can contain local variables declared by var expression (5.10), as well as local functions declared by function expressions (5.11). These are available within the block and within sub-blocks, but not outside the block. Also, they are available only after their declaration. The following example uses var, but the same rules apply to function usage:

{ 
    a; // error, a is not declared yet 
    var a = 1; // declare a 
    a; // ok, a was declared
    {
        a; // ok, a is available in sub-blocks 
    }
    // ok, a is still available after 
    // sub-blocks 
    a; 
} 
a; // error, a is not available outside

在运行时，块从头至尾执行。控制流（如异常（第5.18节）或者返回表达式（第5.19节））可能在所有的表达式被执行之前离开块。

At runtime, blocks are evaluated from top to bottom. Control flow (e.g. exceptions (5.18) or return expressions (5.19)) may leave a block before all expressions are evaluated.