Operator @（取地址）

• 来源: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgOpAt
• 最后更新: 2019-07-04

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返回字符串字面量、变量、对象或过程的地址。

语法

declare operator @ ( byref rhs as T ) as T pointer

用法

result = @ rhs

参数

rhs

要获取地址的字符串字面量、变量、对象或过程。

T

任何标准、用户定义或过程类型。

返回值

返回右侧操作数（rhs）的地址。

描述

Operator @（取地址）返回其操作数的内存地址。

当操作数是 String 类型时，返回内部字符串描述符的地址。使用 Operator Strptr（字符串指针）来获取字符串数据的地址。

操作数不能是数组，但可以是数组元素。例如，"@myarray(0)" 返回 "myarray(0)" 的地址。

此运算符可以使用适当的语法作为成员 Operator 为用户定义类型重载。

示例

start GeSHi

'This program demonstrates the use of the @ operator.

Dim a As Integer
Dim b As Integer

Dim addr As Integer Ptr

a = 5   'Here we place the values 5 and 10 into a and b, respectively.
b = 10

'Here, we print the value of the variables, then where in memory they are stored.
Print "The value in A is ";a;" but the pointer to a is ";@a
Print "The value in B is ";b;" but the pointer to b is ";@b

'Now, we will take the integer ptr above, and use @ to place a value into it.
'Note that the * will check the value in the ptr, just as @ checked the ptr
'for a normal variable.

addr = @a

Print "The pointer addr is now pointing at the memory address to a, value: ";*addr

addr = @b

Print "The pointer addr is now pointing at the memory address to b, value: ";*addr

end GeSHi

start GeSHi

'This program demonstrates how the @ symbol can be used
'to create pointers to subroutines.

Declare Sub mySubroutine ()

Dim say_Hello As Sub()

say_Hello = @mySubroutine   'We tell say_Hello to point to mySubroutine.
                            'The sub() datatype acts as a pointer here.

say_Hello() 'Now we can run say_Hello just like mySubroutine.

Sub mySubroutine
    Print "hi"
End Sub

end GeSHi

方言差异

• 在 -lang qb 方言中，此运算符不能被重载。

与 QB 的差异

• FreeBASIC 新增功能

参见

• Varptr
• Procptr
• Operator * (Value of)
• 指针

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