A struct is an ordered collection of data fields, that can be manipulated as a single item. In other terms, you may think of a struct as a record, or part of a record.
The API often uses pre-defined structs, but these are UNO structs, a highly-specialized kind of struct.
With the Type...End Type statements, you can define your own (non-UNO) structs:
Type aMenuItem 'assign the name of the type 'Define the data fields within the struct. Each ' definition looks like a Dim statement, without the "Dim". aCommand as String aText as String End Type 'close the definition
The Type definition is only a pattern or template, not a set of actual variables. To make an instance of the type — actual variables that can be read and stored — use the Dim as New statement:
Dim maItem as New aMenuItem
As shown in the example below, the Type definition may be written at the start of a module (before the first Sub or Function). The definition will then be available to all routines in the module.
As of OpenOffice.org Version 3.0, unlike variables, there is no way to make the definition accessible outside of the module.
An instance of the new type is a variable, and follows the usual rules for variable scope (see Scope and Life Span of Variables).
An example of how to use the definition, and how to reference the fields within an instance, appears in the section on With...End With.
In general, Basic does not look inside a container, such as an Object, to see what names might be defined there. If you want to use such a name, you must tell Basic where to look. You do that by using the name of the object as a qualifier. Write it before the inner name, and separate it by a period:
Since containers may hold other containers, you may need more than one qualifier. Write the qualifiers in order, from outer to inner:
These names may also be described as, "concatenated with the dot-operator ('.')".
The With Alternative
The With...End With bracketing statements provide an alternative to writing out all the qualifiers, every time – and some of the qualifiers in the API can be quite long. You specify the qualifiers in the With statement. Until Basic encounters the End With statement, it looks for partly-qualified names: names that begin with a period (unary dot-operator). The compiler uses the qualifiers from the With as though they were written in front of the partly-qualified name.
Example 1: A User-defined Struct
This example shows how you may define and use a struct, and how to reference the items within it, both with and without With. Either way, the names of the data fields (from the Type definition) must be qualified by the name of the instance (from the Dim statement).
Type aMenuItem aCommand as String aText as String End Type Sub Main 'Create an instance of the user-defined struct. ' Note the keyword, "New". Dim maItem as New aMenuItem With maItem .aCommand = ".uno:Copy" .aText = "~Copy" End With MsgBox "Command: " & maItem.aCommand & Chr(13) _ & "Text: " & maItem.aText End Sub
Example 2: Case statement
In Cells and Ranges, the following example has the qualifiers in the Case statements written out completely, for clarity. You can write it more easily, this way:
Dim Doc As Object Dim Sheet As Object Dim Cell As Object Doc = ThisComponent Sheet = Doc.Sheets(0) Cell = Sheet.getCellByPosition(1,1) 'Cell "B2" (0-based!) Cell.Value = 1000 With com.sun.star.table.CellContentType Select Case Cell.Type Case .EMPTY MsgBox "Content: Empty" Case .VALUE MsgBox "Content: Value" Case .TEXT MsgBox "Content: Text" Case .FORMULA MsgBox "Content: Formula" End Select End With
Notice that the With construct must be entirely outside of the Select construct.
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