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Programming Conventions

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Matt Fryer edited this page Feb 19, 2015 · 12 revisions

Programming Conventions

Structure

The QVC source code is divided into components to help make it easier to understand and maintain. The component files are named: Qvc_Component.qvs

Naming conventions

All names (except for local variables) should use capitalized full spellings with no spaces and no abbreviations.

  • Examples:
    BaseData
    PrimaryKey

Acronyms may be used but only the first letter should be capitalized.

  • Examples:
    Qvd
    Html
    QvdFilename

All externally visible API components; subroutines, functions, variables – will begin with the namespace prefix “Qvc.”

  • Subroutines: Qvc.function Examples:
    Qvc.Log Qvc.FileExists

Any member preceded by “_” is private to Qvc. It should not be referenced by user script.

Variable Names

Global Variables

Configuration and inter-subroutine communication is done using global variables. Variables should be named Qvc.component.v.name

  • Examples: Qvc.Log.v.LogFilename

The component portion of the name generally matches the subroutine name. However, in some cases, a more general name is used when the variable is used by one or more subroutines.

Any variable preceded by “_” is private to Qvc. It should not be referenced in user script.

Private global variables are used to communicate between routines or to maintain state between calls of the same routine. Private globals should use the 'Qvc.*' convention preceded by “_”.

  • Examples:
    _Qvc.Loader.v.QvdFile

Global variables must be deleted (nullified) in Qvc.Cleanup. Only variables definitely useful to the UI should persist.

Local Variables

Parameter variables automatically have local scope and will not exist outside the SUB. Therefore there is no need to worry about name collisions. It is recommended that parameter variables be named with a leading “_” to clearly note that they are local variables.

  • Examples:
    _tableName

Local variables created in a SUB should be named with a leading “_qvctemp.”

  • Examples:
    _qvctemp.nextValue

Local variables must be deleted (nullified) at the end of the sub using a SET.

  • Examples:
    SET _qvctemp.nextValue =;

It is currently under discussion as to whether this is good enough or whether a reserved _qvclocal.* should be introduced to prevent collision with user names.

Table and Field Names

All temporary tables and fields should be prefixed with the leading “_qvctemp.”

  • Examples:
    _qvctemp.TableName:
    LOAD FieldName AS _qvctemp.FieldName FROM ....

In case the user has called QUALIFY *; in the script prior to making the subroutine call, UNQUALIFY "_qvctemp.*"; should be called before loading any temporary tables.

Return Values

True/False values should be set as -1/0, not True()/False().

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