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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 meth-ods. methods.
       ods.

       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 defi-nition definition
              nition 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 wid-get's widget's
              get'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 partic-ular particular
              ular 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 num-bers, numbers,
       bers,  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://source -
       forge.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)