4D Doc Center : BLOB TO DOCUMENT

4D v13.4

BLOB

BLOB TO DOCUMENT


BLOB TO DOCUMENT ( document ; blob {; *} )

Parameter	Type	Description
document	String	Name of the document
blob	BLOB	New contents for the document
*	Operator	On Macintosh only: Resource fork is written if * is passed; otherwise, Data fork is written

Description

BLOB TO DOCUMENT rewrites the whole contents of document using the data stored in blob. You can pass the name of a document in document. If the document does not exist, the command creates it. If you pass the name of an existing document, make sure that it is not already open, otherwise an error is generated. If you want to let the user choose the document, use the commands Open document or Create document and use the process variable document (see example).

Notes regarding Macintosh:

Macintosh documents can be composed of two forks: the Data fork and the Resource fork. By default, the command BLOB TO DOCUMENT rewrites the Data fork of the document. To rewrite the Resource fork of the document instead, pass the optional * parameter. On Windows, the optional * parameter is ignored.
The documents generated by this command do not have a "type". If you want to create a document with a type, you must use the SET DOCUMENT TYPE command.

Example

You write an Information System that enables you to quickly store and retrieve documents. In a data entry form, you create a button which allows you to save a document that will contain the data previously loaded into a BLOB field. The method for this button could be:

 $vhDocRef:=Create document("") ` Save the document of your choice

 If(OK=1) ` If a document has been created

    CLOSE DOCUMENT($vhDocRef) ` We don't need to keep it open

    BLOB TO DOCUMENT(Document;[YourTable]YourBLOBField) ` Write the document contents

    If(OK=0)

  ` Handle error

    End if

 End if

System variables and sets

OK is set to 1 if the document is correctly written, otherwise OK is set to 0 and an error is generated.

Error Handling

If you try to rewrite a document that does not exist or that is already open by another process or application, the appropriate File Manager error is generated.
The disk space may be insufficient for writing the new contents of the document.
I/O errors can occur while writing the document.

In all cases, you can trap the error using an ON ERR CALL interruption method.