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







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








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 ...?












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.



  

  
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.

  

  
Returns a list of records that have been defined.

  

  
Returns the instances that have been instantiated by
    recordName.

  

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

  

  
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.

  

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

  

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

  

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

  

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










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 {}
%









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



  

  
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.

  










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



  

  
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.

  

  
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.










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
%









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.








data structures, record, struct








Data structures








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








  

    1.2.1
    struct