struct::record(n)             Tcl Data Structures            struct::record(n)



______________________________________________________________________________

NAME
       struct::record - Define and create records (similar to 'C' structures)

SYNOPSIS
       package require Tcl  8.2

       package require struct::record  ?1.2.1?

       record define recordName recordMembers ?instanceName1 instanceName2
       ...?

       record show record

       record show instances recordName

       record show members recordName

       record show values instanceName

       record exists record recordName

       record exists instance instanceName

       record delete record recordName

       record delete instance instanceName

       recordName instanceName|#auto ?-member1 value1 -member2 value2 ...?

       instanceName cget ?-member1 -member2 ...?

       instanceName configure ?-member1 value1 -member2 value2 ...?

_________________________________________________________________

DESCRIPTION
       The ::struct::record package provides a mechanism to group variables
       together as one data structure, similar to a 'C' structure. The members
       of a record can be variables or other records. However, a record can
       not contain circular record, i.e. records that contain the same record
       as a member.

       This package was structured so that it is very similar to how Tk
       objects work. Each record definition creates a record object that
       encompasses that definition. Subsequently, that record object can
       create instances of that record. These instances can then be
       manipulated with the cget and configure methods.

       The package only contains one top level command, but several sub
       commands (see below). It also obeys the namespace in which the record
       was define, hence the objects returned are fully qualified.

       record define recordName recordMembers ?instanceName1 instanceName2
       ...?
              Defines a record. recordName is the name of the record, and is
              also used as an object command. This object command is used to
              create instances of the record definition. recordMembers are the
              members of the record that make up the record definition. These
              are variables and other record. If optional instanceName args
              are given, then an instance is generated after the definition is
              created for each instanceName.

       record show record
              Returns a list of records that have been defined.

       record show instances recordName
              Returns the instances that have been instantiated by recordName.

       record show members recordName
              Returns the members that are defined for record recordName. It
              returns the same format as how the records were defined.

       record show values instanceName
              Returns a list of values that are set for the instance
              instanceName. The output is a list of key/value pairs. If there
              are nested records, then the values of the nested records will
              itself be a list.

       record exists record recordName
              Tests for the existence of a record with the name recordName.

       record exists instance instanceName
              Tests for the existence of a instance with the name
              instanceName.

       record delete record recordName
              Deletes recordName, and all instances of recordName. It will
              return an error if the record does not exist.

       record delete instance instanceName
              Deletes instance with the name of instanceName. It will return
              an error if the instance does not exist.

RECORD MEMBERS
       Record members can either be variables, or other records, However, the
       same record can not be nested witin itself (circular). To define a
       nested record, you need to specify the record keyword, along the with
       name of the record, and the name of the instance of that nested record.
       For example, it would look like this:

              # this is the nested record
              record define mynestedrecord {
                  nest1
                  nest2
              }

              # This is the main record
              record define myrecord {
                  mem1
                  mem2
                  {record mynestedrecord mem3}
              }


       You can also assign default or initial values to the members of a
       record, by enclosing the member entry in braces:

              record define myrecord {
                  mem1
                  {mem2 5}
              }


       All instances created from this record definition, will initially have
       5 as the value for mem2. If no default is given, then the value will be
       the empty string.

       Getting Values

       To get a value of a member, there are several ways to do this.

       [1]    To get a member value, then use the instance built-in cget
              method:

              instanceName cget -mem1

       [2]    To get multiple member values, you can specify them all in one
              command:

              instanceName cget -mem1 -mem2

       [3]    To get a list of the key/value of all of the members, there are
              3 ways:

              - instanceName cget

              - instanceName configure

              - instanceName

       [4]    To get a value of a nested member, then use the dot notation:

              instanceName cget -mem3.nest1

       Setting Values

       To set a value of a member, there are several ways to do this.

       [1]    To set a member value, then use the instance built-in configure
              method:

              instanceName configure -mem1 val1

       [2]    To set multiple member values, you can specify them all in one
              command:

              instanceName configure -mem1 va1 -mem2 val2

       [3]    To set a value of a nested member, then use the dot notation:

              instanceName configure -mem3.nest1 value

       Alias access

       In the original implementation, access was done by using dot notation
       similar to how 'C' structures are accessed. However, there was a
       concensus to make the interface more Tcl like, which made sense.
       However, the original alias access still exists. It might prove to be
       helpful to some.

       Basically, for every member of every instance, an alias is created.
       This alias is used to get and set values for that member. An example
       will illustrate the point, using the above defined records:

              # Create an instance first
              % myrecord inst1
              ::inst1
              % # To get a member of an instance, just use the
              % # alias (it behaves like a Tcl command):
              % inst1.mem1
              %
              % # To set a member via the alias, just include
              % # a value (optionally the equal sign - syntactic sugar)
              % inst1.mem1 = 5
              5
              % inst1.mem1
              5
              % # For nested records, just continue with the
              % # dot notation (note no equal sign)
              % inst1.mem3.nest1 10
              10
              % inst1.mem3.nest1
              10
              % # just the instance by itself gives all
              % # member/values pairs for that instance
              % inst1
              -mem1 5 -mem2 {} -mem3 {-nest1 10 -nest2 {}}
              % # and to get all members within the nested record
              % inst1.mem3
              -nest1 10 -nest2 {}
              %



RECORD COMMAND
       The following subcommands and corresponding arguments are available to
       any record command:

       recordName instanceName|#auto ?-member1 value1 -member2 value2 ...?
              Using the recordName object command that was created from the
              record definition, instances of the record definition can be
              created. Once a instance is created, then it inherits the
              members of the record definition, very similar to how objects
              work. During instance generation, an object command for the
              instance is created as well, using instanceName. This object
              command is used to access the data members of the instance.
              During the instantiation, values for that instance can be given,
              but all values must be given, and be given in key/value pairs.
              Nested records, need to be in list format.

              Optionally, #auto can be used in place of instanceName. When
              #auto is used, then a instance name will automatically be
              generated, of the form recordName<integer>, where <integer> is a
              unique integer (starting at 0) that is generated.

INSTANCE COMMAND
       The following subcommands and corresponding arguments are available to
       any record instance command:

       instanceName cget ?-member1 -member2 ...?
              Each instance has the sub command cget associated with it. This
              is very similar to how Tk widget's cget command works. It
              queries the values of the member for that particular instance.
              If no arguments are given, then a key/value list is returned.

       instanceName configure ?-member1 value1 -member2 value2 ...?
              Each instance has the sub command configure associated with it.
              This is very similar to how Tk widget's configure command works.
              It sets the values of the particular member for that particular
              instance. If no arguments are given, then a key/value list is
              returned.

EXAMPLES
       Two examples are provided to give an good illustration on how to use
       this package.

       Example 1

       Probably the most obvious example would be to hold contact information,
       such as addresses, phone numbers, comments, etc. Since a person can
       have multiple phone numbers, multiple email addresses, etc, we will use
       nested records to define these. So, the first thing we do is define the
       nested records:

              ##
              ##  This is an interactive example, to see what is
              ##  returned by each command as well.
              ##

              % namespace import ::struct::record::*

              % # define a nested record. Notice that country has default 'USA'.
              % record define locations {
                  street
                  street2
                  city
                  state
                  zipcode
                  {country USA}
                  phone
              }
              ::locations
              % # Define the main record. Notice that it uses the location record twice.
              % record define contacts {
                  first
                  middle
                  last
                  {record locations home}
                  {record locations work}
              }
              ::contacts
              % # Create an instance for the contacts record.
              % contacts cont1
              ::cont1
              % # Display some introspection values
              % record show records
              ::contacts ::locations
              % #
              % record show values cont1
              -first {} -middle {} -last {} -home {-street {} -street2 {} -city {} -state {} -zipcode {} -country USA -phone {}} -work {-street {} -street2 {} -city {} -state {} -zipcode {} -country USA -phone {}}
              % #
              % record show instances contacts
              ::cont1
              % #
              % cont1 config
              -first {} -middle {} -last {} -home {-street {} -street2 {} -city {} -state {} -zipcode {} -country USA -phone {}} -work {-street {} -street2 {} -city {} -state {} -zipcode {} -country USA -phone {}}
              % #
              % cont1 cget
              -first {} -middle {} -last {} -home {-street {} -street2 {} -city {} -state {} -zipcode {} -country USA -phone {}} -work {-street {} -street2 {} -city {} -state {} -zipcode {} -country USA -phone {}}
              % # copy one record to another record
              % record define contacts2 [record show members contacts]
              ::contacts2
              % record show members contacts2
              first middle last {record locations home} {record locations work}
              % record show members contacts
              first middle last {record locations home} {record locations work}
              %


       Example 1

       This next example just illustrates a simple linked list

              % # define a very simple record for linked list
              % record define llist {
                  value
                  next
              }
              ::llist
              % llist lstart
              ::lstart
              % lstart config -value 1 -next [llist #auto]
              % [lstart cget -next] config -value 2 -next [llist #auto]
              % [[lstart cget -next] cget -next] config -value 3 -next "end"
              % set next lstart
              lstart
              % while 1 {
              lappend values [$next cget -value]
              set next [$next cget -next]
              if {[string match "end" $next]} {break}
              }
              % puts "$values"
              1 2 3
              % # cleanup linked list
              % # We could just use delete record llist also
              % foreach I [record show instances llist] {
              record delete instance $I
              }
              % record show instances llist
              %



BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will undoubtedly contain
       bugs and other problems.  Please report such in the category struct ::
       record of the Tcllib SF Trackers
       [http://sourceforge.net/tracker/?group_id=12883].  Please also report
       any ideas for enhancements you may have for either package and/or
       documentation.

KEYWORDS
       data structures, record, struct

CATEGORY
       Data structures

COPYRIGHT
       Copyright (c) 2002, Brett Schwarz <brett_schwarz@yahoo.com>




struct                               1.2.1                   struct::record(n)
