struct::record(3tcl) Tcl Data Structures struct::record(3tcl)______________________________________________________________________________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 cre‐
ate 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 com‐
mands (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 instance‐
Name. 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 instance‐
Name.
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 con‐
census 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 mem‐
bers 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 gener‐
ated, 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://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(3tcl)
