全局变量，Perl中的子程序变量问题 [英] Global Variable, subroutine variable Question in Perl

问题描述

$ b

  sub foo（）如何将子程序变量值转换为另一个子程序变量，我可以使用全局变量。 {
 
 my $ myvar =你好; 
} 
 
 sub foo1（）{
 my $ myvar1 = $ myvar; ＃我如何从$ myvar获得Hello。 
} 
  

我尝试使用包和全局变量，但失败了。

 软件包栏; 
我们的$ bar; 
  

谢谢。

解决方案

  {my $ myvar $ 
你可以在包含2个函数的作用域中声明该变量： b 
 $ b sub foo {
 $ myvar =Hello; 
} 
 
 sub foo1 {
 my $ myvar1 = $ myvar; 
 
 
 
 
 $ b $ p 
 $ b 
虽然这不是很优雅，但可能很难因为在 foo1 中设置 $ myvar 的值时不清楚。 
  sub foo {
 my $ myvar =Hello ; 
返回$ myvar; 
} 
 
 sub foo1 {
 my（$ myvar）= @_; 
 my $ myvar1 = $ myvar; 
} 
 
＃调用代码
 my $ myvar = foo（）; 
 foo1（$ myvar）; 
  
请注意，所有3  $ myvar 是不同的变量，在不同的范围。
 
 
 
作为一个方面说明，使用原型（ sub foo（））可能不是一个好主意，除非你真的知道他们在做什么，这可能并非如此（参见关于原型讨论原型的问题）
How can I transfer the subroutine variable value into another subroutine variable, Can I use global variable.
sub foo(){

my $myvar = "Hello";
} 

sub foo1(){
my $myvar1 = $myvar;   # how can I get the "Hello" from $myvar.
}
I tried to use package and global variable, but failed.
Package Bar;
our $bar;
Thank you.
解决方案
You could declare the variable in a scope that includes the 2 functions:
{ my $myvar

  sub foo{
    $myvar = "Hello";
  } 

  sub foo1{
    my $myvar1 = $myvar;   
  }
}
That is not really elegant though, and can be hard to maintain, as it is not clear in foo1 where the value of $myvar was set. It is probably better to pass the variable as an argument.
sub foo {
    my $myvar = "Hello";
    return $myvar;
}

sub foo1 {
  my( $myvar)= @_;
  my $myvar1 = $myvar;
}

# calling code
my $myvar= foo();
foo1( $myvar);
Note that all 3 $myvar are different variables, in different scopes.

As a side note, using prototypes (sub foo()) is probably not a good idea, unless you really know what they are doing, which is likely not to be the case ( see The problem with prototypes for a discussion on prototypes)

                        
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