I have a One to Many relation : One row in modelParent with Many row in modelChild
In a PanelList with the all modelParent rows, I want to hide the delete Icone on the row if the row has children link to this row.
What test should I do ?
Right way
Don't hide the delete button, but show confirmation dialog that would tell user how many related records would be deleted with the selected record. You can find code samples in Project Tracker, People Skills and lots of other templates.
Easy to implement way (worse performance)
Configure prefetch for your ParentModel's datasource to include records from ChildModel
Bind delete button's visibe property to this:
#datasource.item.<NameOfYourRelationField>.length === 0
Harder to implement way (better performance)
You can create calculated model with special flag that you can use on UI to show/hide the delete button. This approach will also require lots of extra scripting for CRUD operations.
Related
I have a Google App Maker project where I have a Many-To-Many Relation between 2 tables A and B.
I can build a page for table A where I have a table of related B records and add new ones using a dialog.
However, this approach enables me to create new B records and associate them to an A record but how can I make the user able to select an existing B record and associate it to an A record via UI?
I will need to have it work both ways (Select A records from B record page as well).
UPDATE:
I was to accomplish this by creating a separate dialog for selecting existing records which would show all available B records in a table widget with a SELECT button on each row. clicking the button will add the record to the B related records of the A record. However, I know there has to be an automatic way built by Google that will be less work and better design.
Thanks and I appreciate your help.
Your solution is a good one, another solution, depending on the number of existing records, is to use the multi-select widget. (You can bind the items to B's datasource, and values to the relation on a record in A. But as I mentioned, this only works well if the number of items in B is small.)
Making this easier is something we've been looking in to, the main challenge is the correct UI in this case depends a lot on the kind of app you're writing.
It took me a while to figure out the bindings for a multi-select but I think I am right in saying that they are
MultiSelect
Datasource: inherited: A
Values: #datasource.item.B
Option: #datasource.B.items
With this that Values are/is what you are updating in A(ie. A.B), but the Options you are updating it with are listed in B(ie. B.items).
Devin Taylor is right in his assertion that if you have a lot of records it may not work so well.
I'm trying to implement multiple record selection feature on a grid.
It is very similar to http://www.tek-tips.com/faqs.cfm?fid=3831
It adds an extra column with check boxes. I want those check boxes!!
But it depends on a extra logical field in the underlying table. It need to create a class clscheck which inherits CHECKBOX. I'm not sure why this CLICK procedure is needed for the checkbox.
PROCEDURE CLICK
IF DODEFAULT()
KEYBOARD '{DNARROW}'
ENDIF
ENDPROC
When I removed it, row selection did not work correctly as expected. Why this?
Here is my requirement:
1) I don't want to add an extra logical field in the underlying table.
2) To work with controls in the grid, I think AllowCellSelection must be .T. I want AllowCellSelection = .F. because I don't need to work with any control in the grid except the check boxes. I need to work only with check boxes. The other columns will be read-only.
3) Can I have selected list without the logical field in the underlying table?
4) Can I remove the usage of KEYBOARD '{DNARROW}'?
In fact, I have a grid which is AllowCellSelection = .F., but it only provides single selection.
I need to enhance it with multiple selection, thus, I just want to add an extra column with check boxes so that user can know he can select multiple records.
No need Shift+Click or Ctrl+Click which is not familiar with idiot users.
I have found this - http://www.tek-tips.com/faqs.cfm?fid=433
It also depends on an extra logical field and it depends Shift+Click and Ctrl+Click.
What you are seeing is quite common for multi-select grids. I've used them SIMILAR to this in the past. However, you are afraid of the extra column in the underlying table. That may/not be true. You don't always have to update the ORIGINAL table, but a temporary CURSOR you are presenting to the user. Ex: If you want to display a list of employees in a table. No, you don't want to keep adding this column to the original employee table as then anyone else trying to do multi-select could falsely get your selection. However, if you pulled into your own local cursor and presented to the user, then no problem. Example...
Thisform.YourGrid.RecordSource = "Employees"
(bound directly to your employee table -- not necessarily the right thing)
vs
use in select( "C_MultiPickEmployees" )
select ;
.F. as IsChosen, ;
E.* ;
from ;
Employees E;
into ;
cursor C_MultiPickEmployees READWRITE
Thisform.YourGrid.RecordSource = "C_MultiPickEmployees"
NOW, you have your extra column without dealing with issues to the underlying table. If you wanted to further filter what you were showing -- such as employees for a certain division/department, then just add that to a WHERE clause, add an Order By if so needed and you are good to go.
As for the "Allow Cell Selection", I've never had to deal with that. I just add a "checkbox" to the first column and set
Thisform.YourGrid.Column[1].CurrentControl = "CheckBoxControl"
(based on the name it is added to the column).
Then, set the column 1's "ControlSource" = "C_MultiPickEmployees.IsChosen" and you should mostly be done.
As for the "CLICK" event trying to force the down arrow. This is more for automatically scrolling to the next record so you can just click, click, click for multiple entries.
Hope this helps clarify things for you.
I'm writing a database access app for storing some data and want to ask a few questions about the model/view architecture.
(Using: Qt 4.7.4, own build; PostgreSQL 9.0; Targets: WinXP, Win7 (32/64 bit))
Let me first explain what I am trying to achieve and where I am currently.
I have two pages (subclassed QWidgets inserted in a QStackedWidget) with a QTableView bound to a model. Each view is bound to a table in the PostgreSQL server. You can add/edit/delete/sort/filter items.
Each page can be seen by only one type of users, lets call the roles Role1 and Role2.
The submit strategies of everything connected to the model are OnManualSubmit.
(Transaction isolation level = Serializable.) When two users want to edit(for example) the same row, I want to do a "SELECT ... FOR UPDATE" query - to make sure that when someone edits something, he will merge his changes with newer ones (if any, just like in SVN for example). But I see only a submitAll() method the QSqlTableModel.
Maybe catching the signals beforeUpdate(), beforeDelete(), beforeInsert() and performing manually "SELECT ... FOR UPDATE" is one option.
The other way I think is to subclass QSqlTableModel. What is the clean and nice way to achieve this?
I want to periodically update the QSqlTableView for each of the pages (one page is seen at most, Role1 users have access only to Page1 and the same for Role2 => Page2).
The first thing that came to my mind is to use a QTimer and manually call select() of the QSqlTableModel, but... not sure if this is the cool way.
I also want to periodically check if the connection to the database is ok, but I think that a QTimer + QSqlDatabase::isOpen () will do.
Now, the 2 tables have the same primary keys and some columns are the same. I want when a user with Role1 changes a row in Table1 to automatically change corresponding columns of Table2 and vice versa. Should I create a trigger in Postgres?
BTW, the database is small - each of the two tables is around 3-4000 rows with ~10 columns (varchars mostly, 1 text and 2 date colunms).
Thanks for reading and Happy New Year! :)
I think you should consider doing something of the following:
Instead of using QSqlTableModel as a model I'd implement my own model as a subclass of QAbstractTableModel. This will allow you a lot of control over what you can do in terms of data manipulation.
One thing that this will require is for certain fields in the table you would need to implement subclass of QAbstractItemDelegate that will allow for modification of data in the table as I am fairly sure you don't want to allow users updating any field in the table as for example primary key is likely have to be left alone.
For question 2 I would suggest implementing a field called transaction_counter for every row so you don't have to select every row in the table just the updated ones the transaction_counter will be updated on every row update and the new one will be inserted on the new row insert. One thing that will be required is that the counter is unique across the table. For example if initial state of the table is: row1 has counter = 0 and row2 has counter = 0. If row1 is updated counter set to 1. When row1 is then updated again counter on it is set to 2. When row2 is now updated counter on it is set to 3, etc. You can certainly do the data refreshes now using QTimer and this will be much more advantageous to for example checking the data as one user may be updating the same table as another user with the same Role.
For Question 3. I don't see any reason why not custom models and especially if you decide to separate data from the model you can manipulate data separately from it's display. Sort of Data->Model->View->Controller implementation. Each one can be maintained separately as long as you have a feedback mechanism for your delegates.
For Question 4. The answer is sure or you can implement the trigger in your application.
Hope this helps. Have a great New Year!
I have a selection list that is generated dynamically, it lists a number of checkboxes that are based on an end-user editable table, as such I have no idea what data, or how much, might be contained in this table and how many checkboxes or what they might contain, other than the primary keys of the table.
The user will select the checks they wish to see, and then control is passed to another page via PostBackUrl. The second page has to figure out which records to show (build it's where clause) based on the checkboxes checked in the previous page.
So, my problem is several-fold. First, asp:CheckBoxes don't have values. This can be worked around by a number of methods. Right now, i'm using a placeholder and dynamically creating the checkboxes in the ItemDataBound event of the DataList. I set the ID to "CheckboxKey1Key2" (where Key1 and Key2 are the primary keys of the check items).
Second, I have to walk through the controls of the PreviousPage to dig out all these values. That in itself is also a pain, but doable.
Now, my thinking is to build the where clause of my Linq2Sql query based on the keys I got from decoding the checked checkbox names. This all seems like a lot of jumping through hoops for something that shouldn't be this difficult. Am I missing something? Does anyone have any better solutions?
Make a class with a structure for your values that will be useful and easy for you to use on the result page. Then when the user clicks whatever it is they click to go to the result page, loop through the DataList, create a collection from the checked items, and you will only need to grab one object instead of everything, when you need to format your query.
Then when you get to the result page, loop through the collection and build the query in the loop. Pretty easy and not much code.
How Can I find all the rows that has been changed in gridview. I can not use Ajax in any form
First get the contents of your grid before it was changed (such as caching the results of the original gridview datasource binding). Then go through the dataset/datatable/however you want to store it, and compare the contents with the current rows of the gridview.
There's no real efficient way to do this, no method like GridView.GetAllChangedRows(). So, what you might do instead is keep a behind the scenes List that you add to each time a row is modified (use the RowUpdated method), then clear this list when needed.
It depends upon how many columns you want to edit in a row.
If you have only one editable column in a row then you can associate a javascript method with that control which you want to modify and in that method you can get a rowid which you can save in another hidden field and in server side you can get all rows whose ids are stored in hidden field.
If you have whole row editable in that case the best approach I think you should save the original data source somewhere and also set a javascript method with rowclick event to get rowid which user selects. Then when user clicks on submit button get all rows whose row ids are stored in hidden field then compare those with same rowid in datasource. This is the best approach from my point of you.
Let me give you an example, suppose there are 1000 rows in a grid and user clicks on only 180 rows. In that case we will compare only 180 rows and wont compare rest of the rows.
Please let me know if somebody has better idea then this.