case 语句中的 Delphi 类型常量

发布于 2024-09-04 23:34:10 字数 535 浏览 7 评论 0原文

在 Delphi 的 case 语句中使用类型化常量的最优雅（或最不难看）的方式是什么？

也就是说，对于这个问题，假设您需要声明一个类型常量，如“

const
  MY_CONST: cardinal = $12345678;
  ...

Then Delphi 编译器不会接受”

case MyExpression of
  MY_CONST: { Do Something };
  ...
end;

，但您需要编写

case MyExpression of
  $12345678: { Do Something };
  ...
end;

这样的常量，这种常量容易出错、难以更新且不优雅。

您可以使用任何技巧来使编译器插入常量的值（最好通过检查源代码中 const 下的常量值，但也可以通过在运行时查找该值）？我们在这里假设您不会在运行时更改“常量”的值。

原文

What is the most elegant (or least ugly) way of using typed constants in a case statement in Delphi?

That is, assume for this question that you need to declare a typed constant as in

const
  MY_CONST: cardinal = $12345678;
  ...

Then the Delphi compiler will not accept

case MyExpression of
  MY_CONST: { Do Something };
  ...
end;

but you need to write

case MyExpression of
  $12345678: { Do Something };
  ...
end;

which is error-prone, hard to update, and not elegant.

Is there any trick you can employ to make the compiler insert the value of the constant (preferably by checking the value of the constant under const in the source code, but maybe by looking-up the value at runtime)? We assume here that you will not alter the value of the "constant" at runtime.

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合约呢 2024-09-11 23:34:10

根据您需要输入常量的原因，您可以尝试类似的操作

const
  MY_REAL_CONST = Cardinal($12345678);
  MY_CONST: Cardinal = MY_REAL_CONST;

case MyExpression of
  MY_REAL_CONST: { Do Something };
  ...
end;

Depending on why you need the constant to be typed you can try something like

const
  MY_REAL_CONST = Cardinal($12345678);
  MY_CONST: Cardinal = MY_REAL_CONST;

case MyExpression of
  MY_REAL_CONST: { Do Something };
  ...
end;

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