evaluate a string as boolean in vb

[saprouzy]

hello there,

i was wondering if there's a way to evaluate a string as a boolean

ie: if bool_str then

do something

end if

with bool_str being something like "varibale1 = variable2" or "RS.recordCount = variable" or more complex things

thanks

[Indigo2005]

Yes, if I understand your question

I remember in C it's

if ( string1 == String2 )
{
allwhatyouwant;
}

In delphi (i think but not sure ...)

if  ( string1 = String2 )
then begin
allwhatyouwant;
end;

The " string1 = string2 " return a boolean value ( true or false )

But you can't do

if ( boolean = string ) then

I hope it's that ...

[saprouzy]

that's not what i meant in my question,

what i want is to use a string as the expression for the if statment

suppose i have this string:

Str = "cmbNames.Text = ""saprouzy"""

cmbNames being a comboBox

i want to a function (ie EvaluateSt) to evaluate Str and return a boolean

If EvaluateSt(Str) Then

do bla

end if

Edited June 25, 2005 by saprouzy

[Indigo2005]

oh ok !

I don't think you can ...

you have to slip your string.

cmbNames.Text is a caracteristic of a component, you can't use it as a string !

[saprouzy]

cmbNames.Text is a caracteristic of a component, you can't use it as a string !

<{POST_SNAPBACK}>

that's exactly what am trying to do.. hehe

[dman]

EDIT: changed. didnt understand at firet.

Think you want "text1.text.tostring" to return string value from textbox

Edited June 25, 2005 by dman

[Delprat]

saprouzy, what you want is not possible, but there is workarounds for specific cases.

With your example :

Str = "cmbNames.Text = ""saprouzy"""

you can enumerate the "Controls" collection of the form (with For Each), check if each control's name is the right name, then check if the control's default/specified property has the right value.

Following code is not tested, but it will show the idea :

dim c as control

for each c in <YourForm>.Controls

if c.name = left$(str, instr(str,".")) then

' c is the right control

if c = right$(str, len(str)-instr(str,"=")) then

' retrun true

endif

endif

next

If you want to check other properties than the default one, you'll need to enumerate each possible property (hardcode them)... that's the line in red : I wrote it for the default property ; if you always check the same property, e.g. the "Tag", replace "c" by "c.Tag".

If you want to check multiple properies, you'll need to extract the property from Str, then string compare it with all other properties (predefined as strings too), then check if the property (not in a string) has the right value.

Did you understood me ?

PS 1: all of this is impossible AFAIK with variables (except if you "hardcode" a small subset).

PS 2: you may prefer to use "Object" instead of "Control" (this will allow you to use recordsets)

bye

[saprouzy]

what you suggested is interesting, but i guess it only works for simple cases

what i wanted to do is for more complex stuff, for example

Str = "cmbText = SomeFunction(someArg)"

if Str then

do bla

end if

i guess it's impossible

[saprouzy]

is there a way to get the list of declared variables?