class::struct.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

.IX Item "Scalar ($ or *$)"
The element is a scalar, and by default is initialized to \f(CW\*(C`undef\*(C'\fR
(but see \*(L"Initializing with new\*(R").
.Sp
The accessor's argument, if any, is assigned to the element.
.Sp
If the element type is \f(CW\*(Aq$\*(Aq\fR, the value of the element (after
assignment) is returned. If the element type is \f(CW\*(Aq*$\*(Aq\fR, a reference
to the element is returned.
.ie n .IP "Array (\*(Aq@\*(Aq\fR or \f(CW\*(Aq*@\*(Aq)" 4
.el .IP "Array (\f(CW\*(Aq@\*(Aq\fR or \f(CW\*(Aq*@\*(Aq\fR)" 4
.IX Item "Array (@ or *@)"
The element is an array, initialized by default to \f(CW\*(C`()\*(C'\fR.
.Sp
With no argument, the accessor returns a reference to the
element's whole array (whether or not the element was
specified as \f(CW\*(Aq@\*(Aq\fR or \f(CW\*(Aq*@\*(Aq\fR).
.Sp
With one or two arguments, the first argument is an index
specifying one element of the array; the second argument, if
present, is assigned to the array element.  If the element type
is \f(CW\*(Aq@\*(Aq\fR, the accessor returns the array element value.  If the
element type is \f(CW\*(Aq*@\*(Aq\fR, a reference to the array element is
returned.
.Sp
As a special case, when the accessor is called with an array reference
as the sole argument, this causes an assignment of the whole array element.
The object reference is returned.
.ie n .IP "Hash (\*(Aq%\*(Aq\fR or \f(CW\*(Aq*%\*(Aq)" 4
.el .IP "Hash (\f(CW\*(Aq%\*(Aq\fR or \f(CW\*(Aq*%\*(Aq\fR)" 4
.IX Item "Hash (% or *%)"
The element is a hash, initialized by default to \f(CW\*(C`()\*(C'\fR.
.Sp
With no argument, the accessor returns a reference to the
element's whole hash (whether or not the element was
specified as \f(CW\*(Aq%\*(Aq\fR or \f(CW\*(Aq*%\*(Aq\fR).
.Sp
With one or two arguments, the first argument is a key specifying
one element of the hash; the second argument, if present, is
assigned to the hash element.  If the element type is \f(CW\*(Aq%\*(Aq\fR, the
accessor returns the hash element value.  If the element type is
\&\f(CW\*(Aq*%\*(Aq\fR, a reference to the hash element is returned.
.Sp
As a special case, when the accessor is called with a hash reference
as the sole argument, this causes an assignment of the whole hash element.
The object reference is returned.
.ie n .IP "Class (\*(AqClass_Name\*(Aq\fR or \f(CW\*(Aq*Class_Name\*(Aq)" 4
.el .IP "Class (\f(CW\*(AqClass_Name\*(Aq\fR or \f(CW\*(Aq*Class_Name\*(Aq\fR)" 4
.IX Item "Class (Class_Name or *Class_Name)"
The element's value must be a reference blessed to the named
class or to one of its subclasses. The element is not initialized
by default.
.Sp
The accessor's argument, if any, is assigned to the element. The
accessor will \f(CW\*(C`croak\*(C'\fR if this is not an appropriate object
reference.
.Sp
If the element type does not start with a \f(CW\*(Aq*\*(Aq\fR, the accessor
returns the element value (after assignment). If the element type
starts with a \f(CW\*(Aq*\*(Aq\fR, a reference to the element itself is returned.
.ie n .Sh "Initializing with ""new"""
.el .Sh "Initializing with \f(CWnew\fP"
.IX Subsection "Initializing with new"
\&\f(CW\*(C`struct\*(C'\fR always creates a constructor called \f(CW\*(C`new\*(C'\fR. That constructor
may take a list of initializers for the various elements of the new
struct.
.PP
Each initializer is a pair of values: \fIelement name\fR\f(CW\*(C` => \*(C'\fR\fIvalue\fR.
The initializer value for a scalar element is just a scalar value. The 
initializer for an array element is an array reference. The initializer
for a hash is a hash reference.
.PP
The initializer for a class element is an object of the corresponding class,
or of one of it's subclasses, or a reference to a hash containing named 
arguments to be passed to the element's constructor.
.PP
See Example 3 below for an example of initialization.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
.IP "Example 1" 4
.IX Item "Example 1"
Giving a struct element a class type that is also a struct is how
structs are nested.  Here, \f(CW\*(C`Timeval\*(C'\fR represents a time (seconds and
microseconds), and \f(CW\*(C`Rusage\*(C'\fR has two elements, each of which is of
type \f(CW\*(C`Timeval\*(C'\fR.
.Sp
.Vb 1
\&    use Class::Struct;
\&
\&    struct( Rusage => {
\&        ru_utime => \*(AqTimeval\*(Aq,  # user time used
\&        ru_stime => \*(AqTimeval\*(Aq,  # system time used
\&    });
\&
\&    struct( Timeval => [
\&        tv_secs  => \*(Aq$\*(Aq,        # seconds
\&        tv_usecs => \*(Aq$\*(Aq,        # microseconds
\&    ]);
\&
\&        # create an object:
\&    my $t = Rusage\->new(ru_utime=>Timeval\->new(), ru_stime=>Timeval\->new());
\&
\&        # $t\->ru_utime and $t\->ru_stime are objects of type Timeval.
\&        # set $t\->ru_utime to 100.0 sec and $t\->ru_stime to 5.0 sec.
\&    $t\->ru_utime\->tv_secs(100);
\&    $t\->ru_utime\->tv_usecs(0);
\&    $t\->ru_stime\->tv_secs(5);
\&    $t\->ru_stime\->tv_usecs(0);
.Ve
.IP "Example 2" 4
.IX Item "Example 2"
An accessor function can be redefined in order to provide
additional checking of values, etc.  Here, we want the \f(CW\*(C`count\*(C'\fR
element always to be nonnegative, so we redefine the \f(CW\*(C`count\*(C'\fR
accessor accordingly.
.Sp
.Vb 2
\&    package MyObj;
\&    use Class::Struct;
\&
\&    # declare the struct
\&    struct ( \*(AqMyObj\*(Aq, { count => \*(Aq$\*(Aq, stuff => \*(Aq%\*(Aq } );
\&
\&    # override the default accessor method for \*(Aqcount\*(Aq
\&    sub count {
\&        my $self = shift;
\&        if ( @_ ) {
\&            die \*(Aqcount must be nonnegative\*(Aq if $_[0] < 0;
\&            $self\->{\*(AqMyObj::count\*(Aq} = shift;
\&            warn "Too many args to count" if @_;
\&        }
\&        return $self\->{\*(AqMyObj::count\*(Aq};
\&    }
\&
\&    package main;
\&    $x = new MyObj;
\&    print "\e$x\->count(5) = ", $x\->count(5), "\en";
\&                            # prints \*(Aq$x\->count(5) = 5\*(Aq
\&
\&    print "\e$x\->count = ", $x\->count, "\en";
\&                            # prints \*(Aq$x\->count = 5\*(Aq
\&
\&    print "\e$x\->count(\-5) = ", $x\->count(\-5), "\en";
\&                            # dies due to negative argument!
.Ve
.IP "Example 3" 4
.IX Item "Example 3"
The constructor of a generated class can be passed a list
of \fIelement\fR=>\fIvalue\fR pairs, with which to initialize the struct.
If no initializer is specified for a particular element, its default
initialization is performed instead. Initializers for non-existent
elements are silently ignored.
.Sp
Note that the initializer for a nested class may be specified as
an object of that class, or as a reference to a hash of initializers
that are passed on to the nested struct's constructor.
.Sp
.Vb 1
\&    use Class::Struct;
\&
\&    struct Breed =>
\&    {
\&        name  => \*(Aq$\*(Aq,
\&        cross => \*(Aq$\*(Aq,
\&    };
\&
\&    struct Cat =>
\&    [
\&        name     => \*(Aq$\*(Aq,
\&        kittens  => \*(Aq@\*(Aq,
\&        markings => \*(Aq%\*(Aq,
\&        breed    => \*(AqBreed\*(Aq,
\&    ];
\&
\&
\&    my $cat = Cat\->new( name     => \*(AqSocks\*(Aq,
\&                        kittens  => [\*(AqMonica\*(Aq, \*(AqKenneth\*(Aq],
\&                        markings => { socks=>1, blaze=>"white" },
\&                        breed    => Breed\->new(name=>\*(Aqshort\-hair\*(Aq, cross=>1),
\&                   or:  breed    => {name=>\*(Aqshort\-hair\*(Aq, cross=>1},
\&                      );
\&
\&    print "Once a cat called ", $cat\->name, "\en";
\&    print "(which was a ", $cat\->breed\->name, ")\en";
\&    print "had two kittens: ", join(\*(Aq and \*(Aq, @{$cat\->kittens}), "\en";
.Ve
.SH "Author and Modification History"
.IX Header "Author and Modification History"
Modified by Damian Conway, 2001\-09\-10, v0.62.
.PP
.Vb 11
\&   Modified implicit construction of nested objects.
\&   Now will also take an object ref instead of requiring a hash ref.
\&   Also default initializes nested object attributes to undef, rather
\&   than calling object constructor without args
\&   Original over\-helpfulness was fraught with problems:
\&       * the class\*(Aqs constructor might not be called \*(Aqnew\*(Aq
\&       * the class might not have a hash\-like\-arguments constructor
\&       * the class might not have a no\-argument constructor
\&       * "recursive" data structures didn\*(Aqt work well:
\&                 package Person;
\&                 struct { mother => \*(AqPerson\*(Aq, father => \*(AqPerson\*(Aq};
.Ve
.PP
Modified by Casey West, 2000\-11\-08, v0.59.
.PP
.Vb 1
\&    Added the ability for compile time class creation.
.Ve
.PP
Modified by Damian Conway, 1999\-03\-05, v0.58.
.PP
.Vb 1
\&    Added handling of hash\-like arg list to class ctor.
\&
\&    Changed to two\-argument blessing in ctor to support
\&    derivation from created classes.
\&
\&    Added classname prefixes to keys in hash\-based classes
\&    (refer to "Perl Cookbook", Recipe 13.12 for rationale).
\&
\&    Corrected behaviour of accessors for \*(Aq*@\*(Aq and \*(Aq*%\*(Aq struct
\&    elements.  Package now implements documented behaviour when
\&    returning a reference to an entire hash or array element.
\&    Previously these were returned as a reference to a reference
\&    to the element.
.Ve
.PP
Renamed to \f(CW\*(C`Class::Struct\*(C'\fR and modified by Jim Miner, 1997\-04\-02.
.PP
.Vb 8
\&    members() function removed.
\&    Documentation corrected and extended.
\&    Use of struct() in a subclass prohibited.
\&    User definition of accessor allowed.
\&    Treatment of \*(Aq*\*(Aq in element types corrected.
\&    Treatment of classes as element types corrected.
\&    Class name to struct() made optional.
\&    Diagnostic checks added.
.Ve
.PP
Originally \f(CW\*(C`Class::Template\*(C'\fR by Dean Roehrich.
.PP
.Vb 10
\&    # Template.pm   \-\-\- struct/member template builder
\&    #   12mar95
\&    #   Dean Roehrich
\&    #
\&    # changes/bugs fixed since 28nov94 version:
\&    #  \- podified
\&    # changes/bugs fixed since 21nov94 version:
\&    #  \- Fixed examples.
\&    # changes/bugs fixed since 02sep94 version:
\&    #  \- Moved to Class::Template.
\&    # changes/bugs fixed since 20feb94 version:
\&    #  \- Updated to be a more proper module.
\&    #  \- Added "use strict".
\&    #  \- Bug in build_methods, was using @var when @$var needed.
\&    #  \- Now using my() rather than local().
\&    #
\&    # Uses perl5 classes to create nested data types.
\&    # This is offered as one implementation of Tom Christiansen\*(Aqs "structs.pl"
\&    # idea.
.Ve