TGIS_FieldInfo class

Describes field schema information and field behavior flags.

Available also on: Delphi | .NET | ActiveX | Python.

Syntax

// Java
public class TGIS_FieldInfo extends TGIS_Object {
};

// Oxygene
type
  TGIS_FieldInfo = public class( TGIS_Object )
  end;

Inheritance

→ TGIS_Object

Constructors

Inherited Overrides Protected

	Name	Visibility	Description
	TGIS_FieldInfo()	public	Create an instance.

Methods

Inherited Overrides Protected

	Name	Visibility	Description
	checkFlags	protected	Validates field settings and updates cumulative flags.
	Clone	public	Creates a copy of this field information object.

Properties

Inherited Protected

Name	Visibility	Description
Binary	public	Binary width for TAB/DAT files.
Decimal	public	Decimal as represented in saved version.
Deleted	public	Indicates whether the field should be deleted on save.
ExportName	public	Name of the field to use during export.
FieldType	public	Type of field.
FileFormat	public	Indicates whether the field is specific to a file format and should not be visible.
Flags	public	Set of cumulative field flags.
Formula	public	Formula to calculate a value.
Hidden	public	Indicates whether the field is hidden in controls.
IsUID	public	Indicates whether the field is used as GIS_UID and will be exported.
Name	public	Name as represented in saved version.
NewDecimal	public	New decimal size of field.
NewName	public	New name of field.
NewWidth	public	New width of field.
ReadOnly	public	Indicates whether the field value cannot be modified.
Rules	public	Field rules.
Saved	public	Indicates whether the field exists in the saved disk-based layer.
Temporary	public	Indicates whether the field is temporary and not stored in a file.
Width	public	Width as represented in saved version.

Remarks

Calculated field

To set a calculated field, you must assign the Formula property a formula in the SQL query format (compabible with TGIS_SqlQuery) that calculates the value for that field, e.g.

fld.Formula = "num*10"

After saving a layer, the formula definition will be saved to the .fld file. Example file definition :

[TatukGIS Field Formulas]
CALC=num*float/10
 
[TatukGIS Fields]

Example

procedure CreateFieldFormula ;
var
  shp : TGIS_Shape ;
  lv  : TGIS_LayerVector ;
  fld : TGIS_FieldInfo ;
  val : Double ;
begin
  // create a layer and fields definition
  lv := TGIS_LayerVector.Create ;
  try
    lv.Open ;
    lv.AddField( 'name', TGIS_FieldType.String, 1, 0 ) ;
    lv.AddField( 'num', TGIS_FieldType.Number, 5, 0 ) ;
    lv.AddField( 'float', TGIS_FieldType.Float, 10, 5 ) ;
    lv.AddField( 'calc', TGIS_FieldType.Float, 10, 5 ) ;
 
    // create a formula for a calculated field
    fld := lv.FieldInfo( lv.Fields.Count-1 ) ;
    fld.Formula := TGIS_FieldFormula.Create( 'num*float/10' ) ;
 
    // create a shape to store field values
    shp := lv.CreateShape( TGIS_ShapeType.Point ) ;
    shp.AddPart ;
    shp.AddPoint( GisPoint(1,1) ) ;
    shp.SetField( 'num', 5 ) ;
    shp.SetField( 'float', 1.1 ) ;
 
    // get a calculated value
    val := VarToDouble( shp.GetField( 'calc' ) ) ;
    Assert.AreEqual( 0.55, val ) ;
 
    // Save and reopen .fld file to restore the formula
    lv.Path := OUTPUT_TEST_PATH + 'test.shp';
    lv.PrepareExportFieldNames( 32 ) ;
    lv.ExportStructureToFLD ;
    lv.ReadFieldDefinition ;    
 
    val := VarToDouble( shp.GetField( 'calc' ) ) ;
    Assert.AreEqual( 0.55, val ) ;    
  finally
    FreeObject( lv ) ;
  end;
end ;

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Table of Contents

TGIS_FieldInfo class

Syntax

Inheritance

Constructors

Methods

Properties

Remarks

Calculated field

Example

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Table of Contents

TGIS_FieldInfo class

Syntax

Inheritance

Constructors

Methods

Properties

Remarks

Calculated field

Example

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