Skip to content

Inline-Initialization.md

Latest commit

 

History

History
72 lines (53 loc) · 3.42 KB

Inline-Initialization.md

File metadata and controls

72 lines (53 loc) · 3.42 KB
Raw
title Inline Variable Initialization
parent Language Syntax
nav_order 14
permalink /Features/Language/Inline-Initialization
index
inline field initialization
field initialization

Inline Variable Initialization

You can now set initial values for variables inline, without needing a line-continuation character.

Examples

Dim i As Long = 1
Dim foo As Boolean = bar()
Dim arr As Variant = Array(1, 2, 3)
Dim strArr(2) As String = Array("a", "b", "c")
Dim cMC As cMyClass = New cMyClass(customConstructorArgs)

What an Initializer Can Use

What the expression after = may contain depends on where the variable is declared.

Dim inside a procedure. Any expression, including a call to a procedure of the project. The initializer runs when execution reaches the declaration, like an assignment on the next line.

A Static variable, a module-level variable, or a field of a class. No call to a procedure of the project: neither one in the same module or class, nor one in another module, called bare or qualified. The call fails with TB5079, Unrecognized symbol, or, qualified, with TB5027, does not contain ... or it is inaccessible in this context. Built-in functions, constants and New, with or without constructor arguments, are allowed:

Class Order
    Private _created As Date = Now()
    Private _lines As Collection = New Collection
    Private _limit As Long = 10 * 1024
End Class

Class Invoice
    Private _id As String = NewId()       ' TB5079: Unrecognized symbol 'NewId'

    Private Function NewId() As String
        NewId = CStr(Int(Rnd * 1000000))
    End Function
End Class

Set a value that needs a procedure of the project in code instead: a class field in Class_Initialize or Sub New, a module-level variable in the procedure that first needs it.

An initializer at module or class level can also read a variable, but not every variable:

  • A class field can read a module-level variable. The modules are set up before any object is created.
  • A class field cannot read another field of the same class. Public X As Long = A + 1, where A is a field, compiles, but the build fails with [LINKER] compilation (codegen) error detected in 'MyClass.{fields_init}'. A run in the IDE goes ahead, and the field holds an arbitrary number. Set the field in a constructor.
  • A module-level variable can read a variable declared above it in the same module.
  • A module-level variable should not read another module's variable. Modules are set up one at a time, so the other module's variable may still be 0 or empty. The order is neither the order of the files nor the alphabetical order of the modules' names.

Inline Variable Declaration for For

A counter variable needs no separate Dim statement:

For i As Long = 0 To 10
    '...
Next

is now valid syntax. You can use any type, not just Long.