reference - 如何获取 Itcl 类成员变量的引用？

Question

假设我有以下结构：

package require Itcl


itcl::class AAA {

private variable m_list {}

constructor {} {
    fill m_list list
}

}

如何在 m_list 上获取参考以便编写

foreach elem $reference {.......} 

考虑到这个列表真的很大，我不想复制它！

Answer 1

Tcl 变量使用写时复制语义。您可以安全地传递一个值，为其分配多个变量，而不必担心它会占用更多内存空间。

例如

set x {some list} ;# there is one copy of the list, one variable pointing at it
set y $x          ;# there is one copy of the list, two variables pointing at it
set z $y          ;# there is one copy of the list, three variables pointing at it
lappend z 123     ;# there are two copies of the list
                  ;# x and y pointing at one
                  ;# z pointing at the other 
                  ;#     which is different from the first via an extra 123 at the end

上面的代码将产生两个巨大的列表，一个包含 x 任意 y 指向的原始数据，另一个包含仅 z 指向的额外元素 123。在 lappend 语句之前，列表只有一份副本，所有三个变量都指向它。

Answer 2

Here is how to get a reference on the member of a class:

package require Itcl


itcl::class AAA {

public variable m_var 5

public method getRef {} {

    return [itcl::scope m_var]
}

}


AAA a

puts [a cget -m_var]

set [a getRef] 10

puts [a cget -m_var]