Delphi label values sorting - delphi

Im trying to sort Label's values. I have lots of labels with an integer value. Labels are called like Label1, Label2, [...], which Im accessing through FindComponent. I have no problem in sorting the integer values Ive stored in an array, but the problem is, after sorting, I have no idea which label had what value. My goal is to like, sort those labels by their value, so I'd get like an array with Labels sorted by their value. Im stuck at this point :(
Eg:
Label1.Caption := 10;
Label2.Caption := 4;
Label3.Caption := 7;
for i := 1 to 3
do some_array[i] := StrToInt(TLabel(FindComponent('Label' + IntToStr(i))).Caption);
sortarray(some_array);
Now, I have sorted array, but Im lacking some sort procedure that would also store label number in the corresponding place. Can someone point me out?

Instead of creating an array of integers, create an array of TLabel controls. This one you can sort the same way as the array of integers. Indeed, given a MyLabel: TLabel, you can easily get the associated integer as StrToInt(MyLabel.Caption).
In addition, the FindComponent approach is not very efficient. I'd do
const
ALLOC_BY = 100;
MAGIC_TAG = 871226;
var
i: Integer;
ActualLength: integer;
FLabels: array of TLabel;
begin
SetLength(FLabels, ALLOC_BY);
ActualLength := 0;
for i := 0 to ControlCount - 1 do
if Controls[i] is TLabel then
with TLabel(Controls[i]) do
if Tag = MAGIC_TAG then
begin
if ActualLength = length(FLabels) then
SetLength(FLabels, length(FLabels) + ALLOC_BY);
FLabels[ActualLength] := Controls[i];
inc(ActualLength);
end;
SetLength(FLabels, ActualLength);
SortArray(FLabels) // with respect to the StrToInt(CurLabel.Caption) of each
// CurLabel: TLabel.
Of course, you can skip the chunk allocating if you know the number of labels in advance.
Make sure that each of the labels that are to be included in the array have the Tag set to MAGIC_TAG.
Another option would be to create an array
FLabelDataArray: array of TLabelData;
of
type
TLabelData = record
Control: TLabel;
Value: integer;
end;
where
FLabelDataArray[i].Value := StrToInt(FLabelDataArray[i].Control.Caption);
is computed only once.

A quick-n-dirty solution that also works in old Delphi versions, is to use TStringList, which has a Sort method and an Objects property that allow you to associate one object to each entry in the list.
Note that the list is sorted in lexicographic order, so the integers must be left padded with zeroes when converted to strings.
var
list: TStringList;
i: integer;
lab: TLabel;
begin
Label1.Caption := '10';
Label2.Caption := '4';
Label3.Caption := '7';
list := TStringList.Create;
try
for i := 1 to 3 do begin
lab := TLabel(FindComponent('Label' + IntToStr(i)));
list.AddObject(Format('%10.10d', [StrToInt(lab.Caption)]), lab);
end;
list.Sort;
for i := 0 to list.Count-1 do
Memo1.Lines.Add(list[i] + #9 + TLabel(list.Objects[i]).Name);
finally
list.Free;
end;
end;
The output would be:
0000000004 Label2
0000000007 Label3
0000000010 Label1
Also, if instead of list.Sort you use list.Sorted := true, you get binary search on list as a bonus (using list.IndexOf or list.Find).
Edit: As Rudy says, visual components such as TLabel should only be used for displaying data, and not for storing and manipulating it. It is recommended to use appropiate data structures for this and to separate the logic of the program from its user interface.

As Andreas says, put the labels into a dynamic array, rather than sorting the values. Once you have them in such an array, sort them like this:
uses
Generics.Defaults, Generics.Collections;
procedure SortLabels(var Labels: array of TLabel);
var
Comparison: TComparison<TLabel>;
Comparer: IComparer<TLabel>;
begin
Comparison := function(const Left, Right: TLabel): Integer
begin
Result := StrToInt(Left.Caption)-StrToInt(Right.Caption);
end;
Comparer := TDelegatedComparer<TLabel>.Create(Comparison);
TArray.Sort<TLabel>(Labels, Comparer);
end;

As others have said, I don't think you're taking the right approach for this task. But, based on your question, a simple hack would be to use the tag property on each label to store its caption's value :
Label1.Caption := '10';
Label1.Tag:=10;
Label2.Caption := '4';
Label2.Tag:=4;
Label3.Caption := '7';
Label3.Tag := 7;
Then you can find the appropriate label by matching the 'array of integer' entry with the label's tag property.
Again: As Rudy and others have commented, your approach to this task is far from desirable, and my solution only conforms to your approach. The tag property itself is a hack built into Delphi, an artifact from ancient times, like 'label' and 'goTo' and really should not be used except out of sheer desperation - like when trying to re-work and retro-fit ancient, poorly written code or if you've got something in prod and you must get in a quick fix for an emergency situation.

Related

Different Results of TScrollBox Population in Delphi and Lazarus

I populate ScrollBoxin the alike way:
procedure TForm1.FormCreate(Sender: TObject);
var
i: word;
begin
for i := 1 to 3 do
begin
with TLabel.Create(ScrollBox1) do
begin
Parent := ScrollBox1;
Top := 1000;
AutoSize := False;
Align := alTop;
Height := 25;
Caption := 'Label' + IntToStr(i);
end;
end;
ScrollBox1.Realign;
end;
When the code is run under Delphi I get the follwong result:
The order of items is proper.
But when I call the same code under Lazarus I get:
The order of items is reverse. I can solve the issue by reverse creation of ScrollBox children and/or adding {IFDEF ...} but I suspect this is not reliable. Adding compiler switches will double the volume of code making it bulky and difficult to read.
Is there a way to do unified reliable Delphi-Lazarus code for this purpose?
APPENDED
explanation on comment of #TomBrunberg
If I create chidren in reverse order (for instance for i := 3 downto 1) I get the opposite result: Delphi produces reverse and Lazarus - direct order. That is why I was saying about doubling of code.
APPENDED 2
on note of Tom Brunberg
When the same code is called from a Button onClick event handler the code behaviour becomes opposite (and again different in Lazarus and in Delphi).
APPENDED 3
Can I trust for i := 1 to 3... Top := 1000 + i; as it gives the expected result?

Loop through records on a cxgrid and update a field/column

I have a cxGrid where I apply a filter to select certain records. When that is done I want to be able to update a field/column in the grid to mark each record that is to be used for the next operation.
I haven't been able to figure this out
Maybe I haven't been specific enough when describing my problem.
I have the cxGrid where I have applied a filter selecting some records.
What I then need to do is to click a columnheader and then have a field called fldselected set to True for these records.
What your updated q is asking for is straightforward and as usual with Devex stuff, it's
all in the OLH as long as you can find your way into it.
A way to find which rows currently match the filter is to use the
cxGrid1DBTableView1.DataController.FilteredRecordIndex[]
property. You can then find that record in the dataset to process it in some way using
cxGrid1DBTableView1.DataController.LocateByKey().
Update: The original version of this answer assumed that the dataset had an integer ID field.
As the OP has said he uses GUIDs instead, I've upddated it accordingly.
Assuming the TClientDataSet CDS1 has fields Guid : TGuidField, Name : TStringfield, size 32
and Selected : TBooleanField and is connected to
a cxDBTableView, with filtering enabled, of a TcxGrid.
Make sure the cxGrid1DBTableView1.DataController.KeyFieldNames is set to 'Guid'.
Add a regular TDBGrid to the form and point it at the same datasource as the TcxGrid. The point
of this is to make it easy to verify that the code is working as required.
Add the code below to the unit, and point cxDBTableView1's OnColumnHeaderClick at
the handler cxGrid1DBTableView1ColumnHeaderClick, and the form's OnCreate at the FormCreate.
Compiler & run
Code:
procedure TForm1.cxGrid1DBTableView1ColumnHeaderClick(Sender: TcxGridTableView;
AColumn: TcxGridColumn);
begin
if AColumn = cxGrid1DBTableView1Name then
ProcessFilteredRecords;
end;
procedure TForm1.FormCreate(Sender: TObject);
var
AGuid : TGuid;
i : Integer;
lResult : Longint;
begin
CDS1.IndexFieldNames := 'Name';
CDS1.CreateDataSet;
for i:= 0 to 6 do begin
lResult := SysUtils.CreateGUID(AGuid);
CDS1.Insert;
CDS1.FieldByName('Name').AsString := Chr(Ord('A') + i);
CDS1.FieldByName('Guid').AsString := GuidToString(AGuid);
CDS1.FieldByName('Selected').AsBoolean := False;
CDS1.Post;
end;
CDS1.First;
end;
procedure TForm1.ProcessFilteredRecords;
var
V : Variant;
i,
Index: Integer;
BM : TBookMark;
begin
BM := CDS1.GetBookMark;
CDS1.DisableControls;
try
for i := 0 to cxGrid1DBTableView1.DataController.FilteredRecordCount - 1 do begin
Index := cxGrid1DBTableView1.DataController.FilteredRecordIndex[i];
// Next, get the GUID value of the row
V := cxGrid1DBTableView1.DataController.Values[Index, 0];
if cxGrid1DBTableView1.DataController.LocateByKey(V) then begin
CDS1.Edit;
CDS1.FieldByName('Selected').AsBoolean := True;
CDS1.Post;
end;
end;
finally
CDS1.EnableControls;
CDS1.GotoBookmark(BM);
CDS1.FreeBookmark(BM);
end;
end;
Check out https://www.devexpress.com/Support/Center/Question/Details/A1095, the article from Dev Express. Don't let the fact that the article is 11 years old fool you. The same technique still applies. And you can set this up either in code or in the grid editor.
Create the column in the grid editor.
Set the columns DataBinding.ValueType to Boolean (if that's what you want the checkbox to represent)
Set the Data Controller's KeyFieldNames property. Very important! I have spent hours scratching my head with an non-functioning unbound column only to find that the KeyFieldNames wasn't set.
An unbound column can be referenced in your next operation using the DataController Records or Values array, depending on how you set that up. Because it is unbound you cannot reference it through the underlying DataSet though.

How do I split alternating lines of a text file into two arrays?

How would I read data from a text file into two arrays? One being string and the other integer?
The text file has a layout like this:
Hello
1
Test
2
Bye
3
Each number corresponds to the text above it. Can anyone perhaps help me? Would greatly appreciate it
var
Items: TStringList;
Strings: array of string;
Integers: array of Integer;
i, Count: Integer;
begin
Items := TStringList.Create;
try
Items.LoadFromFile('c:\YourFileName.txt');
// Production code should check that Items.Count is even at this point.
// Actual arrays here. Set their size once, because we know already.
// growing your arrays inside the iteration will cause many reallocations
// and memory fragmentation.
Count := Items.Count div 2;
SetLength(Strings, Count);
SetLength(Integers, Count);
for i := 0 to Count - 1 do
begin
Strings[i] := Items[i*2];
Integers[i] := StrToInt(Items[i*2+1]);
end;
finally
Items.Free;
end;
end
I would read the file into a string list and then process it item by item. The even ones are put into the list of strings, and the odd ones go into the numbers.
var
file, strings, numbers: TStringList;
...
//create the lists
file.LoadFromFile(filename);
Assert(file.Count mod 2=0);
for i := 0 to file.Count-1 do
if i mod 2=0 then
strings.Add(file[i])
else
numbers.Add(file[i]);
I'd probably use some helper functions called odd and even in my own code.
If you wanted the numbers in a list of integers, rather than a string list, then you would use TList<Integer> and add StrToInt(file[i]) on the odd iterations.
I've used lists rather than dynamic arrays for the ease of writing this code, but GolezTrol shows you how to do it with dynamic arrays if that's what you prefer.
That said, since your state that the number is associated with the string, you may actually be better off with something like this:
type
TNameAndID = record
Name: string;
ID: Integer;
end;
var
List: TList<TNameAndID>;
Item: TNameAndID;
...
List := TList<TNameAndID>.Create;
file.LoadFromFile(filename);
Assert(file.Count mod 2=0);
for i := 0 to file.Count-1 do begin
if i mod 2=0 then begin
Item.Name := file[i];
end else begin
Item.ID := StrToInt(file[i]);
List.Add(Item);
end;
end;
end;
The advantage of this approach is that you now have assurance that the association between name and ID will be maintained. Should you ever wish to sort, insert or remove items then you will find the above structure much more convenient than two parallel arrays.

How can I search faster for name/value pairs in a Delphi TStringList?

I implemented language translation in an application by putting all strings at runtime in a TStringList with:
procedure PopulateStringList;
begin
EnglishStringList.Append('CAN_T_FIND_FILE=It is not possible to find the file');
EnglishStringList.Append('DUMMY=Just a dummy record');
// total of 2000 record appended in the same way
EnglishStringList.Sorted := True; // Updated comment: this is USELESS!
end;
Then I get the translation using:
function GetTranslation(ResStr:String):String;
var
iIndex : Integer;
begin
iIndex := -1;
iIndex := EnglishStringList.IndexOfName(ResStr);
if iIndex >= 0 then
Result := EnglishStringList.ValueFromIndex[iIndex] else
Result := ResStr + ' (Translation N/A)';
end;
Anyway with this approach it takes about 30 microseconds to locate a record, is there a better way to achieve the same result?
UPDATE: For future reference I write here the new implementation that uses TDictionary as suggested (works with Delphi 2009 and newer):
procedure PopulateStringList;
begin
EnglishDictionary := TDictionary<String, String>.Create;
EnglishDictionary.Add('CAN_T_FIND_FILE','It is not possible to find the file');
EnglishDictionary.Add('DUMMY','Just a dummy record');
// total of 2000 record appended in the same way
end;
function GetTranslation(ResStr:String):String;
var
ValueFound: Boolean;
begin
ValueFound:= EnglishDictionary.TryGetValue(ResStr, Result);
if not ValueFound then Result := Result + '(Trans N/A)';
end;
The new GetTranslation function performs 1000 times faster (on my 2000 sample records) then the first version.
THashedStringList should be better, I think.
In Delphi 2009 or later I would use TDictionary< string,string > in Generics.Collections.
Also note that there are free tools such as http://dxgettext.po.dk/ for translating applications.
If THashedStringList works for you, that's great. Its biggest weakness is that every time you change the contents of the list, the Hash table is rebuilt. So it will work for you as long as your list remains small or doesn't change very often.
For more info on this, see: THashedStringList weakness, which gives a few alternatives.
If you have a big list that may be updated, you might want to try GpStringHash by gabr, that doesn't have to recompute the whole table at every change.
I think that you don't use the EnglishStringList(TStringList) correctly. This is a sorted list, you add elements (strings), you sort it, but when you search, you do this by a partial string (only the name, with IndexOfName).
If you use IndexOfName in a sorted list, the TStringList can't use Dicotomic search. It use sequential search.
(this is the implementation of IndexOfName)
for Result := 0 to GetCount - 1 do
begin
S := Get(Result);
P := AnsiPos('=', S);
if (P <> 0) and (CompareStrings(Copy(S, 1, P - 1), Name) = 0) then Exit;
end;
I think that this is the reason of poor performance.
The alternative is use 2 TStringList:
* The first (sorted) only containts the "Name" and a pointer to the second list that contain the value; You can implement this pointer to the second list using the "pointer" of Object property.
* The second (not sorted) list containt the values.
When you search, you do it at first list; In this case you can use the Find method. when you find the name, the pointer (implemented with Object property) give you the position on second list with the value.
In this case, Find method on Sorted List is more efficient that HashList (that must execute a funcion to get the position of a value).
Regards.
Pd:Excuse-me for mistakes with english.
You can also use a CLASS HELPER to re-program the "IndexOfName" function:
TYPE
TStringsHelper = CLASS HELPER FOR TStrings
FUNCTION IndexOfName(CONST Name : STRING) : INTEGER;
END;
FUNCTION TStringsHelper.IndexOfName(CONST Name : STRING) : INTEGER;
VAR
SL : TStringList ABSOLUTE Self;
S,T : STRING;
I : INTEGER;
BEGIN
IF (Self IS TStringList) AND SL.Sorted THEN BEGIN
S:=Name+NameValueSeparator;
IF SL.Find(S,I) THEN
Result:=I
ELSE IF (I<0) OR (I>=Count) THEN
Result:=-1
ELSE BEGIN
T:=SL[I];
IF CompareStrings(COPY(T,1,LENGTH(S)),S)=0 THEN Result:=I ELSE Result:=-1
END;
EXIT
END;
Result:=INHERITED IndexOfName(Name)
END;
(or implement it in a descendant TStrings class if you dislike CLASS HELPERs or don't have them in your Delphi version).
This will use a binary search on a sorted TStringList and a sequential search on other TStrings classes.

How to add up the integer values in a label in delphi

I am currently having problems with screating a scoreboard in Delphi.
I have a series of forms which are individual questions.
If the questions are answered correctly, then the score is 1. Otherwise the score is -1.
On my scoreboard at the moment, I have 12 labels and 11 of them contain the score for each of the forms.
What I would like to do is add up the numbers in each of the labels and output the final score into the 12th label.
Is there a way of doing this?
Any help will be greatly appreciated.
You should use the UI purely for displaying your values.
For working with your data you should use appropriate data structures: array, lists, etc.
Example using an Array:
var
Scores[0..10]: Integer;
Sum: Integer;
procedure CollectData;
var
i: Integer;
begin
Scores[0] := ...;
//...
Scores[10] := ...;
Sum := 0;
for i := Low(Scores) to High(Scores) do
Sum := Sum + Scores[i];
end;
procedure DisplayData;
begin
Label1.Caption := IntToStr(Scores[0]);
//...
Label11.Caption := IntToStr(Scores[10]);
Label12.Caption := IntToStr(Sum);
end;
Neat solution: Keep scores as integers in Integer fields
Not so neat solution:
SumLabel.Caption := IntToStr( StrToIntDef( Label1.Caption, 0 ) + StrToIntDef( Label2.Caption, 0 ) + ... );
Although I think #DR's answer is spot-on, and #Ritsaert's is helpful, here's another option.
Your label components will have a 'TAG' property - you can use this for your own purposes and in your case I'd just set the TAG property at the same time as you set the Caption.
The advantage behind this is that you can format your caption to contain more than a simple number (if you wish), and also you are just summing up tags (which are already integers and don't need you to do the extra work behind a StrToIntDef call). Really, you're following #DR's point about keeping values out of the GUI (in a sense), you're using a storage field in each label instead.
eg;
when setting a score;-
Label1.Caption:=Format('%d point',[FScore]);
Label1.Tag:=FScore;
and when summing them;-
FSum:=Label1.Tag + Label2.Tag + Label3.Tag (etc)

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