Component (Property)

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Modifying a composite key

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Modifying a composite key
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Component (Property)

In french: Composante

Available only with these kinds of connection

The Component property configures the different components of a composite key. You can:

Find out the Nth component of a composite key (defined in the data model editor or through programming).
Define the Nth component of a composite key (Item Description variable).

Versions 17 and later

This property is now available for iPhone/iPad applications.

New in version 17

This property is now available for iPhone/iPad applications.

Versions 18 and later

This property is now available in Windows Store apps mode.

New in version 18

This property is now available in Windows Store apps mode.

Versions 21 and later

This property is now available in Universal Windows 10 App mode.

New in version 21

This property is now available in Universal Windows 10 App mode.

Example

// Define the second component of the composite key
LastFirstName.Component[2] = MaidenName
...
// Validate the data file description
HDescribeFile(Customer)

Syntax

Finding out the Nth component of a composite key Hide the details

<Component name> = <Data file>.<Item>.Component[<N>]

<Component name>: Character string

Name of the item corresponding to the sought component of the composite key.
If N = 1 and if <Item> corresponds to a simple key, <Result> corresponds to the key name.

<Data file>: Character string

Name of the data file used. This name was defined in the data model editor or with the File Description type.

<Item>: Character string

Name of the key item used. This name was defined in the data model editor or with the Item Description type.

<N>: Integer

Number of the component whose name is requested. The number of elements in a composite key is returned by the NbComponent property.

Defining the Nth component of a composite key Hide the details

<Item>.Component[<N>] = <New component name>

<Item>: Character string

Name of the key item used. This name was defined by the Item Description type.

<N>: Integer

Number of the component that must be modified or added. The number of elements in a composite key is returned by the NbComponent property.

<New component name>: Character string

Name of the item that must be used as component of the composite key.

Remarks

Modifying a composite key

Modifying a composite key may allow you to add new components to the composite key during its description through programming. The different components must be numbered in ascending order and no "empty" slot must be found (for example, you cannot go from component 4 to component 6). Otherwise, a WLanguage error occurs.

Remark: It is recommended to use the KeyExpression property to build a composite key in the code.

Error management

A fatal error (WLanguage error) occurs in the following cases:

requested component greater than the number of components found in the key,
writing a component that does not immediately follow the last component of the composite key.