问题
There appears to be a new pragma named parent that does roughly the same thing as base. What does parent do that warrants a new (non-core) module? I am missing something?
回答1:
base tried to do one too many things – automatically handling loading modules but also allowing establishing inheritance from classes already loaded (possibly from a file whose name wasn't based on the module name). To sort of make it work, there was some hackery that caused surprising results in some cases. Rather than break backwards compatibility, a new, replacement pragma parent was introduced with cleaner semantics.
parent will be a core module as of 5.10.1.
Update: forgot that base handles fields (if you are using the fields pragma), which parent doesn't do.
回答2:
Armed with the extra bit of information from ysth, I was able to see the differences in the docs:
The base pragma does the following things:
- adds the named package to
@ISA - loads the module with the same name as the named package using require (unless it detects that the package has already been loaded)
- won't fail if a module with the same name as the package doesn't exist
- dies if there are no symbols in the named package
- if
$VERSIONdoes not exist in named package, base sets it to"-1, set by base.pm" - initializes the fields of the named package if they exist
- does not call the import function of the named package
The parent pragma does the following things:
- adds the named package to
@ISA - loads the module with the same name as the named package using
require - accepts an option that tells it not to die if a module with the same name as the package doesn't exist
来源：https://stackoverflow.com/questions/876471/what-is-the-difference-between-parent-and-base-in-perl-5