6.语言特性 · Haxe 3 手册

**抽象类型**（第2.8节）：一个抽象类型是一个编译时构造，在运行时以一个不同的方式表示。这允许给存在的类型一个全新的意义。 > Abstract types (2.8): > An abstract type is a compile-time construct which is represented in a different way at runtime. This allows giving a whole new meaning to existing types. **外部类**（第6.2节）：外部类可以被用于以一个类型安全的方式描述目标语言特定的交互。 > Extern classes (6.2): > Externs can be used to describe target-speciﬁc interaction in a type-safe manner. **匿名结构**（第2.5节）：数据可以被简单的组织为匿名结构，减少小型数据类的必要性。 > Anonymous structures (2.5): > Data can easily be grouped in anonymous structures, minimizing the necessity of small data classes. ~~~ var point = { x: 0, y: 10 }; point.x += 10; ~~~ **数组推导**（第6.6节）：使用 for 循环和一些逻辑快速创建和填充数组。 > Array Comprehension (6.6): > Create and populate arrays quickly using for loops and logic. ~~~ var evenNumbers = [ for (i in 0...100) if (i\%2==0) i ]; ~~~ **类，接口和继承**（第2.3节）： Haxe允许用类组织代码，使其成为一个面向对象语言。通常相关的功能如Jave等语言所支持的，包括继承和接口。 > Classes, interfaces and inheritance (2.3): > Haxe allows structuring code in classes, making it an object-oriented language. Common related features known from languages such as Java are supported, including inheritance and interfaces. **条件编译**（第6.1节）：条件编译允许根据编译参数编译特定的代码。这有助于抽象目标语言特定的差异，但是也可以用于其他的目的，如更详细的调试。 > Conditional compilation (6.1): > Conditional Compilation allows compiling speciﬁc code depending on compilation parameters. This is instrumental for abstracting target-speciﬁc differences,but can also be used for other purposes, such as more detailed debugging. ~~~ \#if js js.Browser.alert("Hello"); \#elseif sys Sys.println("Hello"); \#end ~~~ **（广义的）代数数据类型**（第2.4节）：结构可以通过代数数据类型（ADT）描述，如Haxe语言中的枚举。除此之外，Haxe支持它们的广义的变体如GADT。 > (Generalized) Algebraic Data Types (2.4): > Structure can be expressed through algebraic data types (ADT), which are known as enums in the Haxe Language. Furthermore, Haxe supports their generalized variant known as GADT. ~~~ enum Result { Success(data:Array<Int>); UserError(msg:String); SystemError(msg:String, position:PosInfos); } ~~~ **内联调用**（第4.4.2节）：函数可以被设计为内联，使它们的代码直接插入调用的位置。通过手动的内联不用使代码重复这可以产生显著的效能提升。 > Inlined calls (4.4.2): > Functions can be designated as being inline, allowing their code to be inserted at call-site. This can yield signiﬁcant performance beneﬁts with out resorting to code duplication via manual inlining. **迭代器**（第6.7节）：迭代一组值，例如一个数组的元素，在Haxe中可以很容易的迭代。定制类可以快速的实现迭代器功能来允许迭代。 > Iterators (6.7): > Iterating over a set of values, e.g. the elements of an array, is very easy in Haxe courtesy of iterators. Custom classes can quickly implement iterator functionality to allow iteration. ~~~ for (i in [1, 2, 3]) { trace(i); } ~~~ **局部函数和闭包**（第5.11节）： Haxe中的函数不限于类字段，并可以被声明为表达式，允许强大的闭包。 > Local functions and closures (5.11): > Functions in Haxe are not limited to class ﬁelds and can be declared in expressions as well, allowing powerful closures. ~~~ var buffer = ""; function append(s:String) { buffer += s; } append("foo"); append("bar"); trace(buffer); // foobar ~~~ **元数据**（第6.9节）：添加元数据到字段，类或者表达式。这可以和编译器、宏，或者运行时的类沟通信息。 > Metadata (6.9): > Add metadata to ﬁelds, classes or expressions. This can communicate information to the compiler, macros, or runtime classes. ~~~ class MyClass { @range(1, 8) var value:Int; } trace(haxe.rtti.Meta.getFields(MyClass).value.range); // [1,8] ~~~ **静态扩展**（第6.3节）：存在的类和其它类型可以被额外的功能来扩展，通过使用静态扩展。 > Static Extensions (6.3): > Existing classes and other types can be augmented with additional functionality through using static extensions. ~~~ using StringTools; " Me & You ".trim().htmlEscape(); ~~~ **字符串插值**（第6.5节）：字符串通过一个单引号声明，可以在当前的上下文访问变量。 > String Interpolation (6.5): > Strings declared with a single quotes are able to access variables in the current context. ~~~ trace(’My name is $name and I work in ${job.industry}’); ~~~ **偏函数应用**（第6.8节）：任何函数可以应用为局部的，提供某些参数的值，然后保留其它的作为之后的字段。 > Partial function application (6.8): > Any function can be applied partially, providing the values of some arguments and leaving the rest to be ﬁlled in later. ~~~ var map = new haxe.ds.IntMap(); var setToTwelve = map.set.bind(_, 12); setToTwelve(1); setToTwelve(2); ~~~ **模式匹配**（第6.4节）：复杂的结构可以被根据模式来匹配，从一个枚举或者一个结构中提取信息，并对特定的值组合定义特定的操作。 > Pattern Matching (6.4): > Complex structures can be matched against patterns, extracting information from an enum or a structure and deﬁning speciﬁc operations for speciﬁc value combination. ~~~ var a = { foo: 12 }; switch (a) { case { foo: i }: trace(i); default: } ~~~ **属性**（第4.2节）：变量类字段可以被涉及为属性，通过定制的read和write访问，可以更精细的访问控制。 > Properties (4.2): > Variable class ﬁelds can be designed as properties with custom read and write access, allowing ﬁne grained access control. ~~~ public var color(get,set); function get_color() { return element.style.backgroundColor; } function set_color(c:String) { trace(’Setting background of element to $c’); return element.style.backgroundColor = c; } ~~~ **访问控制**（第6.10节）：访问控制语言特性使用Haxe元数据语法来禁止或者允许访问类或者字段。 > Access control (6.10): > The access control language feature uses the Haxe metadata syntax to force or allow access classes or ﬁelds. **类型参数、约束和变异**（第3.2节）：类型可以通过类型参数来参数化，使类型化的容器和其它复杂的数据结构可用。类型参数也可以被约束为某些类型并遵守变异规则。 > Type Parameters, Constraints and Variance (3.2): > Types can be parametrized with type parameters, allowing typed containers and other complex data structures. Type parameters can also be constrained to certain types and respect variance rules. ~~~ class Main<A> { static function main() { new Main<String>("foo"); new Main(12); // use type inference } function new(a:A) { } } ~~~