Command: structure

Syntax

structure <name> {
    <data-block>
}

Description

Define an identifier structure (non-graphic).

Parameters

• <name>
  The name of the structure.

Switches

XML characteristics, see here.

Block

Multiple command lines, each of the form:

{<qual>} <type> { <element>{[<num>]} { = <value> } }

where:

• <qual>
  If included, may be one or more of the qualifying words "static" or "heritage".

• <type>
  The identifier type.

• <element>
  The element name, unique for the structure. This is optional, see Notes below.

• <num>
  The array dimension if the element is an array (may be omitted from variable-length arrays).

• <value>
  A class value for the element. When an object of this structure class is created, its element <element> will be assigned the value <value>. This will remain its value until changed by an object member assignment. Only non-array elements can have a class value and only when <type> is one of the following:

blob, channel, epointer, filter, group, layer, menupane, numeric, panel, point, projection, string, time, treenode, window, procedure/function

Values for members of type filter must be single-line definitions.

Notes

Once defined, the structure <name> may be used as a command to create an object of the structure type <name>.

<element> and <num> may be omitted when <type> is another class of structure. In such cases the members of <type> are copied into the new structure and given the same element names.

The structure definition must have application scope, but occurrences of the structure can have any scope.

When structures with graphic elements are required, the commands gstructure or compound should be used.

The qualifying word "static" defines an element to be a class value with the same value for all instances of <name>. Defining elements as static can result in considerable savings of object storage.
Note: for static functions and procedures, the behavior is different to that of static member functions in Java/C++. All functions and procedures, whether static or otherwise, have an implicit first parameter which is an instance of the class. If this is not used (e.g. in a function which simulates Java/C++ behavior) then it should be declared in the function something like args me=generic, and passed to the function by a caller as null.

The qualifying word "heritage" defines an element to be available to child structures. For example, if an element named "t" of a structure is declared heritage, then object.child.child.t is equivalent to object.t.

When the structure class is used to marshal xml input/output, xml characteristics may be applied to the class and to individual class members by means of additional switches. See here for details.

The class command may also be used to define a structure.

Examples

Define the structure.

structure ~admin.person_t {
    string name
    string address[4]
    numeric tel_no
}

Create an occurrence (object) of a person.

~admin.person_t manager

Fill in some of the details.

manager.name = 'Ari van Essen'
manager.tel_no = 7658787

See Also