Eval(exp)

[thatbruce]

The limitations of Eval(exp as expression) are unexplained.
The wiki says "most" expressions are available.
I was hoping that the introduction of multi-line expressions in GB version whatever would allow me to use such type of things as
Select, If Then, For X
This does not appear to be the case.
Has anyone have a better explanation of what can be done and what can't be done.

b

[BruceSteers]

it doesn't seem to like multiline or conditional statements.

Dim sText As String = "If System.Version=3 Then Print 3 Else Print -1"
Eval(sText)

Error "Unexpected If"

This works though
Dim sText As String = "If(System.Version=3, 3, -1)"
Print Eval(sText)

Kinda limited ,

I usually use it to convert text into objects like if i want to get a control/property but all i have is it's name string.
a silly example..

Dim sTBName As String="TextBox1"
Dim sText As String = Eval(sTBName & ".Text")

Or an actual example from my code, where text is left,right,up or down but i want the key.constant , using Object.GetProperty(Key, sKey) gives a bad use of virtual Key class error but Eval works.

Case Like "{left,right,up,down}"
Terminal.MoveCursor(Eval("Key." & sKey), iVal)

But do i have a better explanation ?
probably not, just some observations.

[ocoquet]

Multilines can work !

here is a sample:

Code: Select all

'Class1.class
Public i As Integer
Public a As Integer

Public sub test()

Print Eval("Let Class1.i = 10\nLet Class1.a=100\nLet Class1.i = Class1.i*Class1.a", Null)

end

Print 1000

Regards

[thatbruce]

Yes but.
They are not multi-line expressions, they are just strings.
I cannot put a 40+ line expression into eval.


To better explain.
I have a dozen or so "templates" for an output to a text file. They are in text files that are read in (depending on a context) and consist of lines like:

"obj="&thisobj.ObjectType
"name="&thisobj.Name
"blah="&thisobj.Blah
"blahblah="&thisobj.BlahBlah
etc etc etc

Obviously with a dozen or so templates with up to 60ish lines I don't want to compress the templates to one single line, for coding, execution and debugging purposes.

[ocoquet]

Ok !

I think, the problem is not eval function it's an editor problem, multilines are considered like separate lines, il look in details and come back.

regards
Olivier

[ocoquet]

OK

Form me, it's work nice:

Code: Select all

'Class1.class
Public i As Integer

Public sub test()

Eval("Let Class1.i=\"123\"" &
    "Let Class1.i&=\"456\"" &
    "Let Class1.i&=\"789\"")

Print i

end

Try it

regards
Olivier

[BruceSteers]

sounds like a job for Settings.class

you can add a .Settings As Variant[] property to any class (that does not already have it)

then use Settings.Write() / Settings.Read() on the object

Say for example your objects are in a class called MYObject.class and a $hMyObject instance (just for example)

The MyObject.class like this..

' Gambas class file  (MyObject.class)

Property ObjectType As String Use $sObjectType
Property Name As String Use $sName
Property Blah As Variant Use $vBlah
Property BlahBlah As Variant Use $vBlahBlah

Property Settings As Variant[]

Private Function Settings_Read() As Variant[]

  Return [$sObjectType, $sName, $vBlah, $vBlahBlah]

End

Private Sub Settings_Write(Value As Variant[])

  $sObjectType = Value[0]
  $sName = Value[1]
  $vBlah = Value[2]
  $vBlahBlah = Value[3]

  RefreshData()  '  reload the data into the controls.  In the above code use of something like Me.Name instead of $sName could automate this for you.

End

Then this to Save

Dim hSet as Settings = New Settings(sConfigFile) ' open/set the config file for saving
hSet.Write($hMyObject)   ' save all the .$hMyObject.Settings data you added.
hSet.Save

Then this to Load

Dim hSet as Settings = New Settings(sConfigFile) ' load the config
hSet.Read($hMyObject)   ' set all the object properties according to file data

A more unique Key can be used
hSet.Write($hMyObject,"UniqueName") ' save the object with a name

A default can also be given
hSet.Read($hMyObject, ,"UniqueName", ["Type", "Name", "Blah", "BlahBlah"])