DataField Class

Create a field, which is an object that holds information that defines a particular field in a data server (for example, the field's data type and length).

Inheritance Hierarchy

Object
DataField
SQLValue

Namespace: VO
Assembly: VOSystemClasses (in VOSystemClasses.dll) Version: 2.21

Syntax

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 CLASS DataField

public class DataField

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The DataField type exposes the following members.

Constructors

	Name	Description
	DataField	Construct a data field.

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Properties

	Name	Description
	FieldSpec	The FieldSpec object connected to this field.
	HyperLabel	The hyperlabel connected to this field.
	Name	A string representing the name of the field.
	NameSym	A symbol representing the name of the field.

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Methods

	Name	Description
	AsString	Return the descriptive label defined for this field.

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Remarks

A DataField object is a specific item in a database record. This is in contrast to a FieldSpec object, which is a description of the properties that some field might have. For example, assume you want to create a FieldSpec object that defines an employee number and you have an EMPLOYEE database that has two different fields: EMPNO, which the employee's number (the employee whose record this is), and MGRNO, which is the number of that employee's manager. Thus, you might define the FieldSpec object as follows:

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1CLASS EmployeeNumber INHERIT FieldSpec
2...

and then in the database define two different fields as:

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1DataField{HyperLabel{#EmpNo, "Employee Number"}, ;
2EmployeeNumber{}}
3DataField{HyperLabel{#MgrNo, "Manager Number"}, ;
4EmployeeNumber{}}

Note that some of the field properties can appear redundant given the available FieldSpec properties. For example, the field contains a hyperlabel, but the field's FieldSpec object also contains a hyperlabel. Furthermore, the field's hyperlabel contains a symbolic name, and the FieldSpec's hyperlabel contains a symbolic name. However, this apparent redundancy serves a useful purpose. A FieldSpec's hyperlabel identifies the general class of data (called #EmpNo in this example). This name is often used as the standard name of fields of this type, but it does not have to be, because each particular field has a specific name — in the example above, #EmpNo and #MgrNo. A field, therefore, holds two "groups" of properties: General label information, like its name, caption, description, and help context ID Data type information, stored as a FieldSpec object, that includes data type, length, decimals, validation rules, error messages, diagnostics, and formatting rules In any case, all data-oriented objects in the system have a name and a hyperlabel, which are often shipped around the system for annotation and help purposes.
Important! There is rarely a need for the developer to consider the fields directly as they are typically created through the code generated by the various data server editors.

Reference

VO Namespace