[Solved] Inc limitation

[Windsurfer]

When I used
Inc(ProgressBar1.Position)
rather than
ProgressBar1.Position := ProgressBar1.Position + 1
I received  the error message 'Error: Can't take the address of constant expressions'.

Is this expected behaviour?

In the help file Inc seems to handle various integer types declared as constants.

[engkin]

ProgressBar1.Position is a property, while inc expects a variable.

In case of a property, typically, the compiler provides its value by calling a function, and assigns a new value through a procedure:

Code: [Select]

  TProgressBar = class(TCustomProgressBar)
...
  published
...
    property Position;


Code: [Select]

  TCustomProgressBar = class(TWinControl)
...
  public
...
    property Position: Integer read GetPosition write SetPosition default 0;


[Deepaak]

This is coding error. Inc function cannot be used for incrementing the progressbar.position. Because It is a property which is incremented or decremented by the help of seperate function/procedure. So for updating your progressbar.position please use variable with Inc to acheive this.

[Windsurfer]

Thanks for the helpful comments - so much to know, and so little time...

Component building is on my todo list.

[marcov]

Note that in old (pre 2.6) versions this was possible if the property refered to a field. This was unintended behaviour and removed.

[Zoran]

Note that in old (pre 2.6) versions this was possible if the property refered to a field. This was unintended behaviour and removed.

Actually, it was removed in 2.4: http://wiki.freepascal.org/User_Changes_2.4.0#Treating_direct-mapped_properties_as_regular_fields