delphi 常量数组_如何在Delphi中声明和初始化常量数组

delphi 常量数组

In Delphi, the versatile web-programming language, arrays allow a developer to refer to a series of variables by the same name and to use a number—an index—to tell them apart.

在通用的Web编程语言Delphi中， 数组允许开发人员使用相同的名称引用一系列变量，并使用数字(索引)来区分它们。

In most scenarios, you declare an array as a variable, which allows for array elements to be changed at run-time.

在大多数情况下，您将数组声明为变量，这允许在运行时更改数组元素。

However, sometimes you need to declare a constant array—a read-only array. You cannot change the value of a constant or a read-only variable. Therefore, while declaring a constant array, you must also initialize it.

但是，有时您需要声明一个常量数组-一个只读数组。 您不能更改常量或只读变量的值。 因此，在声明常量数组的同时 ，还必须对其进行初始化。

三个常量数组的示例声明 ( Example Declaration of Three Constant Arrays )

This code example declares and initializes three constant arrays, named Days, CursorMode, and Items.

此代码示例声明并初始化三个名为Days ， CursorMode和Items的常量数组。

• Days is a string array of six elements. Days[1] returns the Mon string.

  天是由六个元素组成的字符串数组。 Days [1]返回Mon字符串。

• CursorMode is an array of two elements, whereby declaration CursorMode[false] = crHourGlass and CursorMode = crSQLWait. "cr*" constants can be used to change the current screen cursor.

  CursorMode是两个元素组成的数组 ，其中声明CursorMode [false] = crHourGlass和CursorMode = crSQLWait。 “ cr *”常量可用于更改当前屏幕光标。

• Items defines an array of three TShopItem records.

  Items定义了三个TShopItem 记录的数组。

type
    TShopItem = record
      Name : string;
      Price : currency;
    end;
 const
    Days : array[0..6] of string =
    (
      'Sun', 'Mon', 'Tue', 'Wed',
      'Thu', 'Fri', 'Sat'
    ) ;
    CursorMode : array[boolean] of TCursor =
    (
      crHourGlass, crSQLWait
    ) ;
    Items : array[1..3] of TShopItem =
    (
      (Name : 'Clock'; Price : 20.99),
      (Name : 'Pencil'; Price : 15.75),
      (Name : 'Board'; Price : 42.96)
    ) ; 

Trying to assign a value for an item in a constant array raises the "Left side cannot be assigned to" compile time error. For example, the following code does not successfully execute:

尝试为常量数组中的项目分配值会导致“无法分配左侧”的编译时间错误。 例如，以下代码无法成功执行：

 Items[1].Name := 'Watch'; //will not compile

翻译自: https://www.thoughtco.com/declare-and-initialize-constant-arrays-1057596

delphi 常量数组