ThinBASIC Core Language > Data types and variables > TYPE (or UDT User Defined Types) > UDT (User Defined Types)

Elements

As the previous chapter mentioned, you need to specify at least one element for user defined type.

Syntax

[STATIC] elementName[(numberOfDimensions)] AS elementType [= value]

Element definition has two mandatory parts:

1.elementName, following the same naming rules as any other variable

2.elementType, which can be any numeric, string or user defined type

Element can be also an array, in such a case you specify number of items in the brackets after the elementName:

TYPE Triangle

point(3) AS Point2D

END TYPE

DIM t AS Triangle

t.point(1).x = 0 : t.point(1).y = 0

t.point(2).x = 2 : t.point(2).y = 0

t.point(3).x = 1 : t.point(3).y = 1

Note: There is one exception, when array does not have to be dimensioned. See Data handling functions if needed.

Static elements

Element can be optionally marked as static. This means, that this field is shared between all the variables of given type.

TYPE Point2D

x AS SINGLE

y AS SINGLE

STATIC description AS STRING

END TYPE

DIM a AS Point2D

a.x = 1 : a.y = 2

a.description = "simple 2D point"

msgBox strformat$("[{1}, {2}] is {3}", a.x, a.y, a.description)

DIM b AS Point2D

b.x = 3 : b.y = 4

msgBox strformat$("[{1}, {2}] is {3}", b.x, b.y, b.description)

Once you run this example, you can see that values of x and y are unique to variables a and b, however, the description of a has been promoted to b due to shared, static nature of the element. This connection works even in the other direction - if you change the static element in b now, it will be immediately reflected in a.

Static elements are the only type of element to have the option of initialization.

TYPE Point2D

x AS SINGLE

y AS SINGLE

STATIC description AS STRING = "Simple 2D Point"

END TYPE

DIM p AS Point2D

msgBox p.description

The example will show "Simple 2D Point" message, because the p variable has the member description initialized in type / end type block.