Macros 晶体中的Tmp宏变量

如何使用宏中的临时变量在Crystal Lang中构建代码。例如，我有：

module Rule
  macro included
    {% rules = [] of TypeDeclaration %}
    
    macro rule(declaration)
        raise("Should be TypeDeclaration") unless \{{declaration.is_a?(TypeDeclaration)}}

        \{% {{rules}} << declaration %}
    end

    macro finished
        \{% for declaration in rules %}
            puts \{{declaration}}
        \{% end %}
    end

  end
end



class StringRule
    include Rule

    rule min : Int32 = 0
    rule max : Int32 = 255
end

模块规则
宏包括
{%rules=[]的类型声明%}
宏规则（声明）
raise（“应该是类型声明”），除非\{declaration.is_a？（类型声明）}
\{%{{rules}}6{%[]宏表达式中的变量的作用域为相应的宏上下文。因此，在包含的
宏中定义的变量在
宏规则中不可见

但您可以为此使用常量：
RULES=[]of
。
\u
下划线使数组不类型化，它仅在编译期间使用，不用于实际代码。如果在宏表达式外部引用
RULES
，编译器将抱怨

module Rule
  macro included
    RULES = [] of _
    
    macro rule(declaration)
      \{% raise("Should be TypeDeclaration") unless declaration.is_a?(TypeDeclaration) %}

      \{% RULES << declaration %}
    end

    macro finished
      \{% for declaration in RULES %}
      puts \{{ declaration.stringify }}
      \{% end %}
    end
  end
end

class StringRule
    include Rule

    rule min : Int32 = 0
    rule max : Int32 = 255
end

模块规则
宏包括
规则=[]共_
宏规则（声明）
\{%raise（“应该是类型声明”），除非声明.is_a？（类型声明）%}
\{%谢谢，这对我来说太好了。
module Rule
  macro included
    RULES = [] of _
    
    macro rule(declaration)
      \{% raise("Should be TypeDeclaration") unless declaration.is_a?(TypeDeclaration) %}

      \{% RULES << declaration %}
    end

    macro finished
      \{% for declaration in RULES %}
      puts \{{ declaration.stringify }}
      \{% end %}
    end
  end
end

class StringRule
    include Rule

    rule min : Int32 = 0
    rule max : Int32 = 255
end