Core Variables

The Variable class is an interface for workspace variables, designed to manage and manipulate various types of variables within a software system. The core oac-tree library supports two types of variable: local and file.

Local Variable

This Variable type defines a variable in memory. These variables can be used (read and written to) from the workspace by instructions. If a variable has a defined type, without a defined value, a zero-initialized AnyValue will be allocated.

Unless the attribute dynamicType is equal to ‘true’, the underlying AnyType of the variable is fixed and all assignments will try to convert to the destination type. The only exception to this rule is when the definition does not include a type. In that case, the variable will be initialized as an Empty type and will have a fixed AnyType from the moment of its first assignment.

When dynamicType is set, all assignments to it will have the semantics of normal AnyValue assignments, i.e. types can change.

Attributes:

Attribute name	Attribute type	Mandatory	Description
type	StringType	no	json style definition of the variable type
value	StringType	no	json style definition of the variable value
dynamicType	BooleanType	no	defines if the variable’s type is dynamic

Example

In the example, two local variables are defined, and variable “a” is copied to variable “b”.

<Sequence>
    <Copy name="copy" inputVar="a" outputVar="b"/>
</Sequence>
<Workspace>
    <Local name="a" type='{"type":"uint8"}' value='1' />
    <Local name="b" type='{"type":"uint8"}' />
</Workspace>

File Variable

This Variable type defines a variable that will read and write values from a file.

A file variable does not impose extra type constraints during assignment. It does however inherit the constraints from the underlying AnyValue, such as immutable element types for arrays.

Attributes:

Attribute name	Attribute type	Mandatory	Description
file	StringType	yes	name of the file where variables are defined
pretty	BooleanType	no	defines if the JSON representation is written with pretty printing

Example

In the example, the variable “input” is copied to the variable “file”, that writes it in the file “/tmp/variable.bck”.

<Sequence>
    <Copy name="copy" inputVar="input" outputVar="file"/>
</Sequence>
<Workspace>
    <Local name="input"
           type='{"type":"MyStruct","attributes":[{"value":{"type":"float32"}}]}'
           value='{"value":0.0}'/>
    <File name="file"
          file="/tmp/variable.bck"/>
</Workspace>