Custom Component and Radio Group

[Aruna]

Hi, I have a custom component that runs Linux 'lsblk' command and then displays the output in a Tmemo. This part works. I want to give the user the ability to select any option in lsblk. The source code is below:

Code: Pascal  [Select][+][-]

1. unit lsblk;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Controls, StdCtrls, Process;
9.  
10. type
11.   { TLSB }
12.   TLSB = class(TCustomControl)
13.   private
14.     FMemo: TMemo;
15.     procedure DoRunCommand;
16.   protected
17.     procedure CreateWnd; override;
18.   public
19.     constructor Create(AOwner: TComponent); override;
20.   published
21.     property Align;
22.     property Anchors;
23.     property Font;
24.     property ParentFont;
25.     property ParentShowHint;
26.     property ShowHint;
27.     property TabOrder;
28.     property TabStop;
29.     property Visible;
30.   end;
31.  
32. procedure Register;
33.  
34. implementation
35.  
36. constructor TLSB.Create(AOwner: TComponent);
37. begin
38.   inherited Create(AOwner);
39.   with GetControlClassDefaultSize do
40.         SetInitialBounds(0, 0, 688, 150);
41.  
42.   // Initialize the memo
43.   FMemo        := TMemo.Create(Self);
44.   FMemo.Parent := Self;
45.   FMemo.Align  := alClient;
46. //FMemo.Width  :=600;
47. //FMemo.Height :=180;
48.   FMemo.Font.Name:= 'Monospace';
49.   //FMemo.ScrollBars := ssVertical;
50.   //Run the command
51.   DoRunCommand;
52. end;
53.  
54. procedure TLSB.CreateWnd;
55. begin
56.   inherited CreateWnd;
57.   // Additional initialization if necessary
58. end;
59.  
60. procedure TLSB.DoRunCommand;
61. var
62.   outstr: string;
63. begin
64.   RunCommand('lsblk', ['-S'], outstr); // @TRon's
65.   FMemo.Lines.Add(outstr);
66. end;
67.  
68. procedure Register;
69. begin
70.   RegisterComponents('Linux Sysinfo', [TLSB]);
71. end;
72.  
73. end.

How would one do this, please?

Right now I am using

Code: Pascal  [Select][+][-]

1. RunCommand('lsblk', ['-S'], outstr);

How would I use a RadioGrop to run the other flags/options/switches?

[bobby100]

Make one more published property of string type for arguments, and use it instead of '-S' in the DoRunCommand.
Do not forget to initialize it to an empty string in the Create method.

Now, the RadioGroup is a part of your main program. You need to a procedure that will inspect the state(s) of the RadioGroup and according to it create a suitable string to pass to your component.

[Aruna]

Make one more published property of string type for arguments, and use it instead of '-S' in the DoRunCommand.
Do not forget to initialize it to an empty string in the Create method.

Now, the RadioGroup is a part of your main program. You need to a procedure that will inspect the state(s) of the RadioGroup and according to it create a suitable string to pass to your component.

Thank you bobby100  I’m very new to object-oriented programming, I would greatly appreciate it if you could provide some example code to help me better understand the concepts.
If it's not too much trouble, could you please share some examples? Thank you very much for your help!

[bobby100]

No problem to help you, but you need to share some more info with me about what your app should do etc.
2nd question - why did you put the part of the code into a separate component? I am referring to the other thread here on the forum.
I would go for a separate component if I have a GUI widget, or if there is a lot of reusable code to make sense for a separate component, unit or class.
If you are doing it for a learning experience - I can understand that, and I will help you.

I would begin with redesigning your component TLSB:
- chose a better name, LSB normally stays for Less Significant Bit. It can lead to some confusion.
- make it more universal, with published properties like Command and Arguments. This way you expand the usability of your component - run any terminal command with arguments and catch the output.

This is how I would do it:

Code: Pascal  [Select][+][-]

1. unit TerminalRun;
2.  
3. {$mode ObjFPC}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Controls, StdCtrls, Process;
9.  
10. type
11.   TTerminalRun = class(TCustomControl)
12.   private
13.     FCommand: string;
14.     FArguments: string;
15.     FMemo: TMemo;
16.     function DoRunCommand: boolean;
17.   protected
18.     procedure CreateWnd; override;
19.   public
20.     constructor Create(AOwner: TComponent); override;
21.     function Run: boolean;
22.   published
23.     property Command: string read FCommand write FCommand;
24.     property Arguments: string read FArguments write FArguments;
25.     property Align;
26.     property Anchors;
27.     property Font;
28.     property ParentFont;
29.     property ParentShowHint;
30.     property ShowHint;
31.     property TabOrder;
32.     property TabStop;
33.     property Visible;
34.   end;
35.  
36. procedure Register;
37.  
38. implementation
39.  
40. constructor TTerminalRun.Create(AOwner: TComponent);
41. begin
42.   inherited Create(AOwner);
43.   with GetControlClassDefaultSize do
44.     SetInitialBounds(0, 0, 688, 150);
45.  
46.   // Initialize the memo
47.   FMemo := TMemo.Create(Self);
48.   FMemo.Parent := Self;
49.   FMemo.Align := alClient;
50.   FMemo.Font.Name := 'Monospace';
51.  
52.   // Initialize the variables
53.   FCommand := '';
54.   FArguments := '';
55. end;
56.  
57. procedure TTerminalRun.CreateWnd;
58. begin
59.   // Do we really need this?
60.   inherited CreateWnd;
61.   // Additional initialization if necessary
62. end;
63.  
64. function TTerminalRun.Run: boolean;
65. begin
66.   Result := False;
67.   if FCommand <> '' then
68.     Result := DoRunCommand;
69. end;
70.  
71. function TTerminalRun.DoRunCommand: boolean;
72. var
73.   outstr: string;
74. begin
75.   Result := RunCommand(FCommand, [FArguments], outstr); // @TRon's
76.   if Result then
77.     FMemo.Lines.Add(outstr)
78.   else
79.     FMemo.Lines.Add('Error executing command ' + FCommand + ' ' + FArguments);
80. end;
81.  
82. procedure Register;
83. begin
84.   RegisterComponents('Linux Sysinfo', [TTerminalRun]);
85. end;
86.  
87. end.

So, I've added two properties - Command and Arguments. I've added a function Run with feedback as boolean. I've converted your DoRunCommand to a function to get feedback. See, the RunCommand is also a function, so you can get a feedback if successfully run or not. We add some checks in Run function and also include this in final feedback. There are better ways to get the error info if the function did not succeed, but let leave it at this simple method for now.
Don't put DoRunCommand in Create method - this is a bad idea because it is also executed in the IDE, at design time. If your DoRunCommand triggers an exception, you will lock your IDE. With my new organization of the code, where you need to set the Command and the Arguments before Run, it won't work anyway. You need to take care about the code that it is executed also in the IDE at the design time, to not lock your IDE.
To use the component, one must set the command and the arguments, and execute the Run function after that. You do this from your main unit/form.

[bobby100]

I just saw a mistake in my code. The FArguments is not a single string but an array. The way I've written it, it will take just one argument.

[Aruna]

No problem to help you, but you need to share some more info with me about what your app should do etc.

I am trying to learn and teach myself by experimenting. I was trying to see if I could build a component that the end-user could use to see the output of all block devices in a linux system. I also wanted to give the end-user the ability to choose which option to run when using lsblk.

2nd question - why did you put the part of the code into a separate component? I am referring to the other thread here on the forum.

Like I said I am very new and trying to learn so that was me experimenting trying to get this working :-)

I would go for a separate component if I have a GUI widget, or if there is a lot of reusable code to make sense for a separate component, unit or class.
If you are doing it for a learning experience - I can understand that, and I will help you.

I was simply trying to teach myself how to create a component that uses lsblk.

I would begin with redesigning your component TLSB:
- chose a better name, LSB normally stays for Less Significant Bit. It can lead to some confusion.
- make it more universal, with published properties like Command and Arguments. This way you expand the usability of your component - run any terminal command with arguments and catch the output.

When initially trying to compile the compiler complained so I used LSB no specific reason or meaning to that. It worked so I used it. It was the first thing that came to my mind. I will choose a better name now. I have near-zero experience with published properties I am trying to learn this.

This is how I would do it:

Code: Pascal  [Select][+][-]

1. unit TerminalRun;
2.  
3. {$mode ObjFPC}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Controls, StdCtrls, Process;
9.  
10. type
11.   TTerminalRun = class(TCustomControl)
12.   private
13.     FCommand: string;
14.     FArguments: string;
15.     FMemo: TMemo;
16.     function DoRunCommand: boolean;
17.   protected
18.     procedure CreateWnd; override;
19.   public
20.     constructor Create(AOwner: TComponent); override;
21.     function Run: boolean;
22.   published
23.     property Command: string read FCommand write FCommand;
24.     property Arguments: string read FArguments write FArguments;
25.     property Align;
26.     property Anchors;
27.     property Font;
28.     property ParentFont;
29.     property ParentShowHint;
30.     property ShowHint;
31.     property TabOrder;
32.     property TabStop;
33.     property Visible;
34.   end;
35.  
36. procedure Register;
37.  
38. implementation
39.  
40. constructor TTerminalRun.Create(AOwner: TComponent);
41. begin
42.   inherited Create(AOwner);
43.   with GetControlClassDefaultSize do
44.     SetInitialBounds(0, 0, 688, 150);
45.  
46.   // Initialize the memo
47.   FMemo := TMemo.Create(Self);
48.   FMemo.Parent := Self;
49.   FMemo.Align := alClient;
50.   FMemo.Font.Name := 'Monospace';
51.  
52.   // Initialize the variables
53.   FCommand := '';
54.   FArguments := '';
55. end;
56.  
57. procedure TTerminalRun.CreateWnd;
58. begin
59.   // Do we really need this?
60.   inherited CreateWnd;
61.   // Additional initialization if necessary
62. end;
63.  
64. function TTerminalRun.Run: boolean;
65. begin
66.   Result := False;
67.   if FCommand <> '' then
68.     Result := DoRunCommand;
69. end;
70.  
71. function TTerminalRun.DoRunCommand: boolean;
72. var
73.   outstr: string;
74. begin
75.   Result := RunCommand(FCommand, [FArguments], outstr); // @TRon's
76.   if Result then
77.     FMemo.Lines.Add(outstr)
78.   else
79.     FMemo.Lines.Add('Error executing command ' + FCommand + ' ' + FArguments);
80. end;
81.  
82. procedure Register;
83. begin
84.   RegisterComponents('Linux Sysinfo', [TTerminalRun]);
85. end;
86.  
87. end.

So, I've added two properties - Command and Arguments. I've added a function Run with feedback as boolean. I've converted your DoRunCommand to a function to get feedback. See, the RunCommand is also a function, so you can get a feedback if successfully run or not. We add some checks in Run function and also include this in final feedback. There are better ways to get the error info if the function did not succeed, but let leave it at this simple method for now.

Thank you for the explanation and really appreciate your help.

Don't put DoRunCommand in Create method - this is a bad idea because it is also executed in the IDE, at design time. If your DoRunCommand triggers an exception, you will lock your IDE. With my new organization of the code, where you need to set the Command and the Arguments before Run, it won't work anyway. You need to take care about the code that it is executed also in the IDE at the design time, to not lock your IDE.
To use the component, one must set the command and the arguments, and execute the Run function after that. You do this from your main unit/form.

Oh dear, no wonder @wp also said do not run commands in the create method. I have much to learn. Thank you for your help and time @bobby100