Friday, 2 June 2017

How to dock a form to a panel programmatically

This is a quick solution to a question I had on how to have a form that is set so it can dock into another form's panel. I have a main form with a panel on the right with the 'Docksite' property set to true. I have another form with the 'DragKind' property set to dkDock and the 'DragMode' set to dmAutomatic. I create the docking form at runtime and wanted it so that by default it was docked into the right panel. The quick solution that I found hard to find on the net is after I create the form do the following:

DockingForm.ManualDock(PanelRight);
DockingForm.Show;

Thursday, 25 May 2017

Frame Inheritance - TabOrder: Property does not exist - Issue Fixed

I've been working on an application recently and it has a few frames (TFrame), I noticed that there were common properties and methods to all the frames, so I decided that they should derive from a base class. I created the base frame class and then in code derived the other frames from the base frame. It all seemed to work fine a build and ran OK, however after closing the project and then coming back to it a few days later, when I tried to open a frame I received an error stating the TabOrder property does not exist, I ignored it and received more property does not exist errors (I did not save any changes). The solution to this problem was simple, in the .dfm file at the top was:

object TestFrame: TTestFrame 

This needed to be changed to:

inherited TestFrame: TTestFrame

The ideal way to do this is at design time when designing the structure of the application, if there is an abstract or concrete frame class then this should be added to the repository so when a developer needs to create a new frame, they can simply inherit the frame from the one in the repository.

This is a very similar problem to inheriting datamodules, I've also had to do something similar. 

Wednesday, 19 April 2017

Only use ShowMessage() function for debugging

I always use the ShowMessage function for debugging while doing development and always exclude it from release code for the following reasons:


  1. MessageDlg or MessageBox functions are much better as a popup dialog than ShowMessage, they have more options and the presentation is better giving the user a visual icon categorising the meaning of the popup.
  2. It is easy to search through all the code and check there is no 'ShowMessage' operational before checking in the code. I had a customer call me once saying they have a popup (ShowMessage) which just says 'Hello', this was because the developer forgot to remove or comment out the ShowMessage before checking in.
  3. Because there is no icon with a ShowMessage, some testers and end users assume the popup is an error dialog. I have had the same but to a lesser extent with MessageDlg, the icon helps to show when it is information, warning or confirmation.
Some developers seem to use ShowMessage to quickly display information to the user, they are using ShowMessage because they think it is quicker to use, but in GExperts there is a Message Dialog tool that creates the code based on the options the developer sets.

There is the argument not to use these popup at all, and in some applications they cause issues. I think that popups can be annoying to the user if used too much, but I do not have a problem with them if they are used sparingly and they do not cause problems with the operation of the application.

I imagine some developers might say you should never use ShowMessage to debug and use breakpoints while debugging, which in most cases is the true, but there are occasions when some testing by the developer might be done in a non-development environment, in which case you cannot use the debugger. 

Wednesday, 15 March 2017

Why are semi-colons sometimes not required?

Over the 20 years I've been developing commercial software one question I still have with the Delphi language is why was the language designed so semi-colons are not required at the end of methods? For example:

function DoSomething: boolean;
begin
  if FDoSomethingElse then
  begin
    DoSomethingElse;
  end
end; 

I believe the reason why the compiler does not complain about this, is because the semi-colon in Delphi is a statement separator and not a terminator. If I modify this function for example:

function DoSomething: boolean;
begin
  if FDoSomethingElse then
  begin
    DoSomethingElse;
  end;
  DoOtherStuff
end;

I obviously need to now add in the semi-colon, but I do not need to add in the semi-colon after 'DoOtherStuff'. I currently cannot see any benefit of leaving the semi-colon out. I would not normally code this way and always add in the semi-colon for 2 reasons:

  1. Adding the semi-colon makes the code more consistent.
  2. It means later on when the code is modified the semi-colon does not have to be added.
I have come across Delphi developers who will not put in the semi-colon if it is not required, but cannot see any real benefit from leaving it out. Maybe I have answered my own question, and that is the semi-colon is a separator and when the language was developed they did not see any pros or cons of just allowing the semi-colon not to be there.


Thursday, 23 February 2017

Strict Private Problem with Code Completion

Some time ago I noticed something annoying in Delphi XE with 'Strict Private' and code completion.

Here is an example:

TMyClass = class(TObject)
strict private

public
    property Test: string read FTest write FTest;
end;

When I do CTRL + Shift + C to add the private member to the class it does the following:

TMyClass = class(TObject)
strict private

private
    FTest: string;

published

public
    property Test: string read FTest write FTest;
end;

It adds FTest to the private section of the class and also adds the published section, which is not what I want, but if I remove 'strict' it does not add the 'published' section. Because of this I develop my classes  as 'private' and then once I have added all the require properties then I add 'strict' if required. I am not sure if this behaviour is some setting somewhere that I am not aware of, or whether this is something that might have changed in more recent versions of Delphi. Is there a valid reason to have a 'published' section when there is a 'strict private' section?

Friday, 27 January 2017

Should constants be uppercase?

In a recent blog someone pointed out to me that boolean values true and false should be uppercase because they are constants. This made me think, usually I put constants in uppercase, however when I code true and false they are always lowercase, so it raises a question about my code style, should all constants be uppercase? If so then true, false and nil should also always be uppercase, but for me this does not look correct. Should constants not be uppercase? One reason why constants are uppercase is so they stand out from variables, but is this the only reason?

When I develop in C#, I follow the recommendation for constants not to be uppercase, so I am starting to feel that maybe this should be the same in Delphi and constants should be camel case for local constants and pascal case for public ones.