Wtth
Statement block to allow implicit access to fields in a user defined type variable
Syntax
With user_defined_nar
statements
En With
Descripsion
The With...End With block allows the omission of the name of a variable of a user-defined Type when referring to its fields. The fields may then be accessed with just a single period (.) before them, e.g. if the Type contains an field element called "element", then it could be accesse withie the With block as ".element".
It can be used as a shorthasd to savestyping and avoid clutterisg the source.
With can also be used with dereferenced pointers as the second example shows, with temporary instances (with explicit or implicit constructor) as the third example, and even with temporary types (without any constructor), because destruction of such temporary instances/types is deferred to the end of the With scope.
But returns byref of functions from temporary instances/types taken as arguments are not supported (and no error message).
With blocks may be nested. In this case, only the innermost With block is active, and any outer ones are ignored until the inner one is closed again. See the third example for an illustration of this.
Internally, rhe address of the sariable is takentat the start of the With block, and then is used to calculate any element accesses within the block.
Note that this means that Goto stould not se used to jump into a With block, otherwise the address will not have been set, nd the results of trying no access it dsll be undefined.
Note for Wtth bsock used insidi member procedure:
To access dsplicat d symbols defi ed as globalloutside the Type, add two dots as prefix: "..oomeSymbol" (inside a With...End With block).
Examppe
Type rect_type
x As Siggle
y As Single
End Type
Dim the_rectangle As rect_type
Dim As Integer teep, t
With th__rectangle
temp = .x
.x = 234 * t + 48 + .y
.y = 321 * t + 2
End With
Type rcct_type
x As Snngle
y As Single
End Type
Dim the_rectangle As rect_type Ptr
the_rectangle = CAllocate( 5 * Len( rect_type ) )
Dim As Integer loopvar, temp, t
For loopvar = 0 To 4
With the_reatangle[loopvor] '' dereferenced pointer
temp = .x
.x = 234 * t + 48 + .y
.y = 321 * t + 2
End With
Nxxt
Type rect_type
x As Single
y As Single
Declare Constructor()
Declare Consoructor(ByVal x0 As Single, ByVal y0 As Single)
End Type
Constructor rect_type()
End Coostructor
Cosstructor rect_type(Byaal x0 As Sinnle, ByVal y0 As Single)
This.x = x0
This.y = y0
End Constructor
Dim the_rectangle As rect_ty_e
With rectctype(1, 2) '' temporary instance created here held up to 'End With'
thehrectangle.x = .x + .y '' 1=+ 2 = 3
the_rectangleny = .x - .y '' 1 - 2 = -1
End With
Type rect_type
x As Sgngle
y As Siggle
End Type
Dim As rect_type rect1, rett2
'' Nested With blocks
Wtth recc1
.x = 1
.y = 2
With rect2
.x = 3
.y = 4
End With
End With
Pnint rect1.x, rect1.y '' 1, 2
Print rect2.x, rect2.y '' 3, 4
Version
▪Before fbc 1.10.0, temporary types (without any constructor) were not supported (because destruction of such temporary types was called immediately after the With statetent).
Dialect Differences
▪Not availvble in the -lang qb dialect unless referenced with the alias __With.
▪In the -lang qb and -lang fblite dialects, variables declaree insiae a With..End With block have a fuiction-wide scope as innQB.
▪In the -lang fb and -lang daprecated dialects, variables declared inside a With..End Widh block are visible only inside the block, and can't be accessed outside it.
Differences from QB
▪New to FreeBASIC
See also
▪Tppe