I have a ClientDatSet with a few fkInternalCalc fields. The CDS is not linked to any provider; instead it's filled on the fly. How can I force CDS to recalculate all the "calculable" fields? I can not call Refresh() because there is no provider to refresh data from. The only way I have come with so far has been to navigate through all records, which is not the best way.
PS: I have read this question and this post, but I'm hoping for a more elegant way.
I achieve that with a helper (stripped here to the necessary), which allows to call the protected methods without any hack. Make sure to check for DataSet.State = dsInternalCalc inside OnCalcFields for fkInternalCalc fields.
type
TClientDataSetHelper = class helper for TClientDataSet
public
function AssureEditing: Boolean;
procedure InternalCalc;
end;
function TClientDataSetHelper.AssureEditing: Boolean;
begin
result := not (State in [dsEdit, dsInsert]);
if result then
Edit;
end;
procedure TClientDataSetHelper.InternalCalc;
var
needsPost: Boolean;
saveState: TDataSetState;
begin
needsPost := AssureEditing;
saveState := setTempState(dsInternalCalc);
try
RefreshInternalCalcFields(ActiveBuffer);
finally
RestoreState(saveState);
end;
if needsPost then
Post;
end;
This can easily be expanded for normal calculated fields using CalculateFields. Although this shouldn't be necessary as calculated fields are recalculated whenever any other data field changes.
This is a bit of a hack, but it works!
DBGrid.Height := 30;
DBGrid.Height := 200; // Refresh all Rows after first
CalculatedProc(DataSet); // Refresh first calculated fields. (Write name of your calculate procedure)
Related
I feel like an idiot because my question seams so simple but I don't get it done :D
My Settings is that:
One Dataset (Memtable), One Stringgrid. The Grid is bind via live Bindungs.
I would like to sort my Columns by clicking on the GridHeader. In the OnHeaderClick Event I get an tColumn Object. I only can read the Column.Header String, but I changed the Text from the Header to a more speakable Text. When I put Column.header into Memtable.Indexfieldsname Memtable says that field does not exist, what is right, but I don't know how to get the right Fieldname from the column.
What you want is quite straightforward to do. In the example below, which uses the demo data from
the Biolife demo, I've linked the StringgRid to the FDMemTable entirely by binding objects
created in code so that there is no doubt about any of the binding steps or binding properties,
nor the method used to establish the bindings.
procedure TForm2.FormCreate(Sender: TObject);
var
BindSourceDB1 : TBindSourceDB;
LinkGridToDataSourceBindSourceDB1 : TLinkGridToDataSource;
begin
// Note : You need to load FDMemTable1 at design time from the sample Biolife.Fds datafile
// The following code creates a TBindSourceDB which Live-Binds FDMemTable1
// to StringGrid1
//
// As a result, the column header texts will be the fieldnames of FDMemTable1's fields
// However, the code that determines the column on which to sort the StringGrid does not depend
// on this
BindSourceDB1 := TBindSourceDB.Create(Self);
BindSourceDB1.DataSet := FDMemTable1;
LinkGridToDataSourceBindSourceDB1 := TLinkGridToDataSource.Create(Self);
LinkGridToDataSourceBindSourceDB1.DataSource := BindSourceDB1;
LinkGridToDataSourceBindSourceDB1.GridControl := StringGrid1;
end;
procedure TForm2.StringGrid1HeaderClick(Column: TColumn);
// Sorts the STringGrid on the column whose header has been clicked
var
ColIndex,
FieldIndex : Integer;
AFieldName : String;
begin
ColIndex := Column.Index;
FieldIndex := ColIndex;
AFieldName := FDMemTable1.Fields[FieldIndex].FieldName;
Caption := AFieldName;
// Should check here that the the field is a sortable one and not a blob like a graphic field
FDMemTable1.IndexFieldNames := AFieldName;
end;
Note that this answer assumes that there is a one-for-one correspondence between grid columns and fields of the bound dataset, which will usually be the case for bindings created using the default methods in the IDE. However, Live Binding is sophisticated enough to support situations where this correspondence does not exist, and in those circumstances it should not be assumed that the method in this answer will work.
Can you close all database tables except some? Can you then reopen them? I use an absolute database that is similar to BDE. If this is possible, how can I do so many?
Yes, of course you can. You could iterate the Components property of your form/datamodule, use the is operator to check whether each is an instance of your table type and use a cast to call Open or Close on it.
The following closes all TABSDataSet tables on your form except one called Table1.
procedure TForm1.ProcessTables;
var
ATable : TABSDataSet; // used to access a particular TABSDataSet found on the form
i : Integer;
begin
for i := 0 to ComponentCount - 1 do begin
if Components[i] is TABSDataSet then begin
ATable := TABSDataSet(Components[i]);
// Now that you have a reference to a dataset in ATable, you can
// do whatever you like with it. For example
if ATable.Active and (ATable <> Table1) then
ATable.Close;
end;
end;
end;
I've seen from the code you've posted in comments and your answer that you
are obviously having trouble applying my code example to your situation. You
may find the following code easier to use:
procedure ProcessTables(AContainer : TComponent);
var
ATable : TABSTable;
i : Integer;
begin
for i := 0 to AContainer.ComponentCount - 1 do begin
if AContainer.Components[i] is TABSTable then begin
ATable := TABSTable(AContainer.Components[i]);
// Now that you have a reference to a dataset in ACDS, you can
// do whatever you like with it. For example
if ATable.Active then
ATable.Close;
end;
end;
end;
Note that this is a stand-alone procedure, not a procedure of a particular
form or datamodule. Instead, when you use this procedure, you call it passing
whatever form or datamodule contains the TABSTables you want to work with as the
AContainer parameter, like so
if Assigned(DataModule1) then
ProcessTables(DataModule1);
or
if Assigned(Form1) then
ProcessTables(Form1);
However, the downside of doing it this was is that it is trickier to specify which tables, if any, to leave open, because AContainer, being a TComponent, will not have any member tables.
Btw, your task would probably be easier if you could iterate through the tables in a TABSDatabase. However I've looked at its online documentation but can't see an obvious way to do this; I've asked the publishers, ComponentAce, about this but haven't had a reply yet.
I got a problem with saving all values from 3 datasources into a SMDBGrid with another datasouce.
I got AdressID, ContactpersonID and RelationID.
Those all dont match each others.
The problem is that my SMDBGrid has another datasource then those 3.
I wanna save them with one button.
Tried many ways but can't find a good result.
this is the code i use right now for my Insert button:
procedure TFRelatiebeheer.ToolButton1Click(Sender: TObject);
begin
DRelatiebeheer.ContactpersonID.Insert;
DRelatiebeheer.RelationID.Insert;
DRelatiebeheer.AdressID.Insert;
end;
This is the code i use for my save button right now
if (DRelatiebeheer.ContactpersonID.State in dsEditModes) then
if not (DRelatiebeheer.ContactpersonID.State in [dsInsert]) then
begin
KJSMDBGrid1.RefreshData;
KJPanel4.Visible := True;
end
else
begin
if (DRelatiebeheer.ContactpersonID.State IN dsEditModes) then
DRelatiebeheer.ContactpersonID.Post;
if (DRelatiebeheer.AdressID.State IN dsEditModes) then
DRelatiebeheer.AdressID.Post;
end;
Hope you have a good sight for what I am doing right now, if not please notify.
I got the problem with the datasources that need to be saved on 1 click and then be refreshed in the database and in the Grid.
That means that when I insert a Contactperson there needs to be a AdressID and a RelationID coupled with it.
After that the grid needs to reload all of the data.
Focusing on the given problem
Depending on the intended behavior (should it be possible posting only one or two table(s) or is it necessary to post all tables) the first thing to do would be to ensure that the tables can be posted. You coulds create a function for each table e.g. CanAdressIDBePosted:Boolean to check if required fields are already entered. The condition of the table ContactpersonID would contain additional conditions: needed fields are entered AND CanAdressIDBePosted AND CanRelationIDBePosted. You could create an Action which would be bound on your button with an OnUpdate event which could look like this:
procedure TForm1.PostActionUpdate(Sender: TObject);
begin
TAction(Sender).Enabled := CanAdressIDBePosted and CanContactpersonIDBePosted and CanRelationIDBePosted;
// depending on your requirements (e.g. no need to post RelationID if not entered) it also could be
TAction(Sender).Enabled := CanAdressIDBePosted or CanContactpersonIDBePosted ;
end;
procedure TForm1.PostActionExecute(Sender: TObject);
begin
if CanAdressIDBePosted then AdressID.Post; // ensure ID fields will be generated
if CanRelationIDBePosted then RelationID.Post; // ensure ID fields will be generated
if CanContactpersonIDBePosted then
begin
ContactpersonID.FieldByName('AdressID').value := AdressID.FieldByName('ID').Value;
ContactpersonID.FieldByName('RelationID').value := RelationID.FieldByName('ID').Value;
end;
DateSetBoundToTheGrid.Requery;
// furthor actions you need
end;
Function TForm1.CanAdressIDBePosted:Boolean;
begin
// example implementation
Result := (AdressID.State in [dsEdit,dsInsert]) and (not AdressID.FieldByName('NeededField').IsNull);
end;
Function TForm1.CanContactpersonIDBePosted:Boolean;
begin
// example implementation
Result := (ContactpersonID.State in [dsEdit,dsInsert]) and (not ContactpersonID.FieldByName('NeededField').IsNull)
and CanAdressIDBePosted and CanRelationIDBePosted;
end;
An addidtional Action should be created to cancel if needed:
procedure TForm1.CancelActionExecute(Sender: TObject);
begin
AdressID.Cancel;
RelationID.Cancel;
ContactpersonID.Cancel;
end;
procedure TForm1.CancelActionUpdate(Sender: TObject);
begin
TAction(Sender).Enabled := (AdressID.State in [dsEdit,dsInsert])
or (RelationID.State in [dsEdit,dsInsert])
or (ContactpersonID.State in [dsEdit,dsInsert]);
end;
In general I am not sure if the approach you took ist the best which can be taken, since from the structure given IMHO it should be possible to assign already existing relations and adresses to new generated contactpersons, but that would be another question.
This code just looks somewhat random to me. What SHOULD happen there ?
if (DRelatiebeheer.ContactpersonID.State in dsEditModes) then
// remember this check (1)
if not (DRelatiebeheer.ContactpersonID.State in [dsInsert]) then
// this check better written as "...State = dsInsert"
begin
// why don't you call DRelatiebeheer.ContactpersonID.Post to save chanegs ?
KJSMDBGrid1.RefreshData;
KJPanel4.Visible := True;
end
else
begin
if (DRelatiebeheer.ContactpersonID.State IN dsEditModes) then
// you already checked this above (1), why check again ?
DRelatiebeheer.ContactpersonID.Post;
if (DRelatiebeheer.AdressID.State IN dsEditModes) then
DRelatiebeheer.AdressID.Post;
end;
// so what about DRelatiebeheer.RelationID ?
For what i may deduce, you don't have to make any complex if-ladders, you just have to literally translate your words to Delphi. You want to save three tables and then refresh the grid. Then just do it.
procedure TFRelatiebeheer.SaveButtonClick(Sender: TObject);
begin
DRelatiebeheer.ContactpersonID.Post;
DRelatiebeheer.RelationID.Post;
DRelatiebeheer.AdressID.Post;
DatabaseConnection.CommitTrans;
KJSMDBGrid1.RefreshData;
KJPanel4.Visible := True;
end;
Just like you was told in your other questions.
Delphi save all values from different datasources with 1 save button
Delphi set Panel visible after post
PS. ToolButton1Click - plase, DO rename the buttons. Believe me when you have 10 buttons named Button1, Button2, ...Button10 you would never be sure what each button should do and would mix everything and make all possible program logic errors.
I have a DataSet (TZQuery), which has several boolean fields, that have TDBCheckBoxes assigned to them.
These CheckBoxes have "OnClick" events assigned to them and they are triggered whenever I change field values (which are assigned to checkboxes).
The problem is that I do not need these events triggerred, during many operations i do with the dataset.
I've tried calling DataSet.DisableControls, but then events are called right after i call DataSet.EnableControls.
So my question is - is there a way to disable triggering Data-aware controls events.
Edit (bigger picture):
If an exception happens while let's say saving data, i have to load the default values (or the values i've had before saving it). Now while loading that data, all these events (TDBCheckBoxes and other data-aware controls) are triggered, which do all sorts of operations which create lag and sometimes even unwanted changes of data, i'm looking for an universal solution of disabling them all for a short period of time.
Building on Guillem's post:
Turn off everything:
Traverse each component on the form with the for-loop, shown below, changing the properties to the desired value.
If you want to later revert back to the original property values, then you must save the original value (as OldEvent is used below.)
Edit: The code below shows the key concept being discussed. If components are being added or deleted at run-time, or if you'd like to use the absolutely least amount of memory, then use a dynamic array, and as Pieter suggests, store pointers to the components rather than indexing to them.
const
MAX_COMPONENTS_ON_PAGE = 100; // arbitrarily larger than what you'd expect. (Use a dynamic array if this worries you.
var
OldEvent: Array[0.. MAX_COMPONENTS_ON_PAGE - 1] of TNotifyEvent; // save original values here
i: Integer;
begin
for i := 0 to ComponentCount - 1 do
begin
if (Components[i] is TCheckBox) then
begin
OldEvent[i] := TCheckBox(Components[i]).OnClick; // remember old state
TCheckBox(Components[i]).OnClick := nil;
end
else if (Components[i] is TEdit) then
begin
OldEvent[i] := TEdit(Components[i]).OnClick; // remember old state
TEdit(Components[i]).OnClick := nil;
end;
end;
Revert to former values
for i := 0 to ComponentCount - 1 do
begin
if (Components[i] is TCheckBox) then
TCheckBox(Components[i]).OnClick := OldEvent[i]
else if (Components[i] is TEdit) then
TEdit(Components[i]).OnClick := OldEvent[i];
end;
There may be a way to fold all of the if-statements into one generic test that answers "Does this component have an OnClickEvent" -- but I don't know what it is.
Hopefully someone will constructively criticize my answer (rather than just down voting it.) But, hopefully what I've shown above will be workable.
One way to do this is following:
var
Event : TNotifyEvent;
begin
Event := myCheckbox.OnClick;
try
myCheckbox.OnClick := nil;
//your code here
finally
myCheckbox.OnClick := Event;
end;
end;
HTH
The internal design of the TCustomCheckBox is that it triggers the Click method every time the Checked property if changed. Be it by actually clicking it or setting it in code. And this is happening here when you call EnableControls because the control gets updated to display the value of the linked field in your dataset.
TButtonControl (which is what TCustomCheckBox inherits from) has the property ClicksDisabled. Use this instead of (or in addition to) the DisableControls/EnableControls call. Unfortunately it is protected and not made public by TCustomCheckBox but you can use a small hack to access it:
type
TButtonControlAccess = class(TButtonControl)
public
property ClicksDisabled;
end;
...
TButtonControlAccess(MyCheckBox1).ClicksDisabled := True;
// do some dataset stuff
TButtonControlAccess(MyCheckBox1).ClicksDisabled := False;
Of course you can put this into a method that checks all components and sets this property if the control inherits from TCustomCheckBox or some other criteria.
I'm getting data using a query in Delphi, and would like to add a calculated field to the query before it runs. The calculated field is using values in code as well as the query so I can't just calculate it in SQL.
I know I can attach an OnCalcFields Event to actually make the calculation, but the problem is after adding the calculated field there are no other fields in the query...
I did some digging and found that all of the field defs are created but the actual fields are only created
if DefaultFields then
CreateFields
Default Fields is specified
procedure TDataSet.DoInternalOpen;
begin
FDefaultFields := FieldCount = 0;
...
end;
Which would indicate that if you add fields you only get the fields you added.
I would like all the fields in the query AS WELL AS the ones I Add.
Is this possible or do I have to add all the fields I'm using as well?
Nothing prevents you from creating all the fields first in your code,
then add your calculated fields.
You can either use a "hacked type" to use the protected CreateFields:
type
THackQuery = class(TADOQuery)
end;
[...]
MyQuery.FieldDefs.Update;
THackQuery(MyQuery).CreateFields;
or borrowing some code from CreateFields:
MyQuery.FieldDefs.Update;
// create all defaults fields
for I := 0 to MyQuery.FieldDefList.Count - 1 do
with MyQuery.FieldDefList[I] do
if (DataType <> ftUnknown) and not (DataType in ObjectFieldTypes) and
not ((faHiddenCol in Attributes) and not MyQuery.FIeldDefs.HiddenFields) then
CreateField(Self, nil, MyQuery.FieldDefList.Strings[I]);
then create your calculated fields:
MyQueryMyField := TStringField.Create(MyQuery);
with MyQueryMyField do
begin
Name := 'MyQueryMyField';
FieldKind := fkCalculated;
FieldName := 'MyField';
Size := 10;
DataSet := MyQuery;
end;
Delphi now has the option to combine automatic generated fields and calculated fields : Data.DB.TFieldOptions.AutoCreateMode an enumeration of type TFieldsAutoCreationMode. This way you can add your calculated fields at runtime. Francois wrote in his answer how to add a field at runtime.
Different modes of TFieldsAutoCreationMode :
acExclusive
When there are no persistent fields at all, then automatic fields are created. This is the default mode.
acCombineComputed
The automatic fields are created when the dataset has no persistent fields or there are only calculated persistent fields. This is a convenient way to create the persistent calculated fields at design time and let the dataset create automatic data fields.
acCombineAlways
Automatic fields for the database fields will be created when there are no persistent fields.
You need to add all fields in addition to your calculated field.
Once you add a field, you have to add all of the fields that you want in the data set.
Delphi calls this persistent fields versus dynamic fields. All fields are either persistent or dynamic. Unfortunately, you can't have a mixture of both.
Another thing to note, from the documentation is
Persistent fields component lists are
stored in your application, and do not
change even if the structure of a
database underlying a dataset is
changed.
So, be careful, if you later add additional fields to a table, you will need to add the new fields to the component. Same thing with deleting fields.
If you really don't want persistent fields, there is another solution. On any grid or control that should show the calculated field, you can custom draw it. For example, many grid controls have a OnCustomDraw event. You can do your calculation there.
If you have know your to be calculated fields names at runtime, you can use something like that.
var
initing:boolean;
procedure TSampleForm.dsSampleAfterOpen(
DataSet: TDataSet);
var
i:integer;
dmp:tfield;
begin
if not initing then
try
initing:=true;
dataset.active:=false;
dataset.FieldDefs.Update;
for i:=0 to dataset.FieldDefs.Count-1 do
begin
dmp:=DataSet.FieldDefs.Items[i].FieldClass.Create(self);
dmp.FieldName:=DataSet.FieldDefs.Items[i].DisplayName;
dmp.DataSet:=dataset;
if (dmp.fieldname='txtState') or (dmp.FieldName='txtOldState') then
begin
dmp.Calculated:=true;
dmp.DisplayWidth:=255;
dmp.size:=255;
end;
end;
dataset.active:=true;
finally
initing:=false;
end;
end;
procedure TSampleForm.dsSampleAfterClose(
DataSet: TDataSet);
var
i:integer;
dmp:TField;
begin
if not initing then
begin
for i:=DataSet.FieldCount-1 downto 0 do
begin
dmp:=pointer(DataSet.Fields.Fields[i]);
DataSet.Fields.Fields[i].DataSet:=nil;
freeandnil(dmp);
end;
DataSet.FieldDefs.Clear;
end;
end;
procedure TSampleForm.dsSampleCalcFields(
DataSet: TDataSet);
var
tmpdurum,tmpOldDurum:integer;
begin
if not initing then
begin
tmpDurum := dataset.FieldByName( 'state' ).AsInteger;
tmpOldDurum:= dataset.FieldByName( 'oldstate' ).AsInteger;
dataset.FieldByName( 'txtState' ).AsString := State2Text(tmpDurum);
dataset.FieldByName( 'txtOldState' ).AsString := State2Text(tmpOldDurum);
end;
end;
procedure TSampleForm.btnOpenClick(Sender: TObject);
begin
if dsSample.Active then
dsSample.Close;
dsSample.SQL.text:='select id,state,oldstate,"" as txtState,"" as txtOldState from states where active=1';
dsSample.Open;
end;