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Struct (3)
  • >> Struct (3) ( Solaris man: Библиотечные вызовы )
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    NAME

         Class::Struct - declare struct-like datatypes as Perl
         classes
    
    
    

    SYNOPSIS

             use Class::Struct;
                     # declare struct, based on array:
             struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
                     # declare struct, based on hash:
             struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });
    
             package CLASS_NAME;
             use Class::Struct;
                     # declare struct, based on array, implicit class name:
             struct( ELEMENT_NAME => ELEMENT_TYPE, ... );
    
             package Myobj;
             use Class::Struct;
                     # declare struct with four types of elements:
             struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );
    
             $obj = new Myobj;               # constructor
    
                                             # scalar type accessor:
             $element_value = $obj->s;           # element value
             $obj->s('new value');               # assign to element
    
                                             # array type accessor:
             $ary_ref = $obj->a;                 # reference to whole array
             $ary_element_value = $obj->a(2);    # array element value
             $obj->a(2, 'new value');            # assign to array element
    
                                             # hash type accessor:
             $hash_ref = $obj->h;                # reference to whole hash
             $hash_element_value = $obj->h('x'); # hash element value
             $obj->h('x', 'new value');        # assign to hash element
    
                                             # class type accessor:
             $element_value = $obj->c;           # object reference
             $obj->c->method(...);               # call method of object
             $obj->c(new My_Other_Class);        # assign a new object
    
    
    
    

    DESCRIPTION

         Class::Struct exports a single function, struct.  Given a
         list of element names and types, and optionally a class
         name, struct creates a Perl 5 class that implements a
         "struct-like" data structure.
    
         The new class is given a constructor method, new, for
         creating struct objects.
    
         Each element in the struct data has an accessor method,
         which is used to assign to the element and to fetch its
         value.  The default accessor can be overridden by declaring
         a sub of the same name in the package.  (See Example 2.)
    
         Each element's type can be scalar, array, hash, or class.
    
         The struct() function
    
         The struct function has three forms of parameter-list.
    
             struct( CLASS_NAME => [ ELEMENT_LIST ]);
             struct( CLASS_NAME => { ELEMENT_LIST });
             struct( ELEMENT_LIST );
    
         The first and second forms explicitly identify the name of
         the class being created.  The third form assumes the current
         package name as the class name.
    
         An object of a class created by the first and third forms is
         based on an array, whereas an object of a class created by
         the second form is based on a hash. The array-based forms
         will be somewhat faster and smaller; the hash-based forms
         are more flexible.
    
         The class created by struct must not be a subclass of
         another class other than UNIVERSAL.
    
         A function named new must not be explicitly defined in a
         class created by struct.
    
         The ELEMENT_LIST has the form
    
             NAME => TYPE, ...
    
         Each name-type pair declares one element of the struct. Each
         element name will be defined as an accessor method unless a
         method by that name is explicitly defined; in the latter
         case, a warning is issued if the warning flag (-w) is set.
    
         Element Types and Accessor Methods
    
         The four element types -- scalar, array, hash, and class --
         are represented by strings -- '$', '@', '%', and a class
         name -- optionally preceded by a '*'.
    
         The accessor method provided by struct for an element
         depends on the declared type of the element.
    
         Scalar ('$' or '*$')
              The element is a scalar, and is initialized to undef.
    
              The accessor's argument, if any, is assigned to the
              element.
    
              If the element type is '$', the value of the element
              (after assignment) is returned. If the element type is
              '*$', a reference to the element is returned.
    
         Array ('@' or '*@')
              The element is an array, initialized to ().
    
              With no argument, the accessor returns a reference to
              the element's whole array.
    
              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 '@', the accessor returns the
              array element value.  If the element type is '*@', a
              reference to the array element is returned.
    
         Hash ('%' or '*%')
              The element is a hash, initialized to ().
    
              With no argument, the accessor returns a reference to
              the element's whole hash.
    
              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 '%', the accessor returns the
              hash element value.  If the element type is '*%', a
              reference to the hash element is returned.
    
         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
              initialized to the result of calling the new
              constructor of the named class.
    
              The accessor's argument, if any, is assigned to the
              element. The accessor will croak if this is not an
              appropriate object reference.
    
              If the element type does not start with a '*', the
              accessor returns the element value (after assignment).
              If the element type starts with a '*', a reference to
              the element itself is returned.
    
    
    

    EXAMPLES

         Example 1
              Giving a struct element a class type that is also a
              struct is how structs are nested.  Here, timeval
              represents a time (seconds and microseconds), and
              rusage has two elements, each of which is of type
              timeval.
    
                  use Class::Struct;
    
                  struct( rusage => {
                      ru_utime => timeval,  # seconds
                      ru_stime => timeval,  # microseconds
                  });
    
                  struct( timeval => [
                      tv_secs  => '$',
                      tv_usecs => '$',
                  ]);
    
                      # create an object:
                  my $t = new rusage;
                      # $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);
    
    
         Example 2
              An accessor function can be redefined in order to
              provide additional checking of values, etc.  Here, we
              want the count element always to be nonnegative, so we
              redefine the count accessor accordingly.
    
                  package MyObj;
                  use Class::Struct;
    
                              # declare the struct
                  struct ( 'MyObj', { count => '$', stuff => '%' } );
    
                              # override the default accessor method for 'count'
                  sub count {
                      my $self = shift;
                      if ( @_ ) {
                          die 'count must be nonnegative' if $_[0] < 0;
                          $self->{'count'} = shift;
                          warn "Too many args to count" if @_;
                      }
                      return $self->{'count'};
                  }
    
    
    
                  package main;
                  $x = new MyObj;
                  print "\$x->count(5) = ", $x->count(5), "\n";
                                          # prints '$x->count(5) = 5'
    
                  print "\$x->count = ", $x->count, "\n";
                                          # prints '$x->count = 5'
    
                  print "\$x->count(-5) = ", $x->count(-5), "\n";
                                          # dies due to negative argument!
    
    
    
    

    Author and Modification History

         Renamed to Class::Struct and modified by Jim Miner, 1997-
         04-02.
    
             members() function removed.
             Documentation corrected and extended.
             Use of struct() in a subclass prohibited.
             User definition of accessor allowed.
             Treatment of '*' in element types corrected.
             Treatment of classes as element types corrected.
             Class name to struct() made optional.
             Diagnostic checks added.
    
         Originally Class::Template by Dean Roehrich.
    
             # 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's "structs.pl"
             # idea.
    
    
    
    


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