Mega Code Archive
TStrings == TMemoField == TStrings
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Title: TStrings == TMemoField == TStrings
Question: whenever you need a MemoField in a database you'll need to somehow display the info, there's no direct way to do it (that I know of =o|)...
Answer:
so, here's a little trick to work around, plus we'll see a little how to work with the useful but not so used Streams
//declare these functions in another unit (make reusable code!)
//I have my functions in the MyDBUtils
//this first function will return the memofield into a TString
Procedure MemoFieldToStrings(FromTable:TTable; Const FieldName:String; GetLines:TStrings);
Var aBlobStream:TBlobStream;
Begin
GetLines.Clear;
aBlobStream:=nil; //this just to eliminate the warning
With FromTable Do
Begin
Try
aBlobStream := TBlobStream.Create(TMemoField(FieldByName(FieldName)), bmRead);
GetLines.LoadFromStream(aBlobStream);
Finally
aBlobStream.Free
End
End
End;
//this function takes 3 parameters, the table where you're gonna get the data from, the field and a TStrings where it'll return back your data
we can still wrap this function so we look up the index, then return the info... something like this:
Procedure GetUsersForGroup(FromTable:TTable; Const GroupName:String; UsersInGroup:TStrings);
Begin
UsersInGroup.Clear;
With FromTable Do
If (FindKey([GroupName])) Then
MemoFieldToStrings(FromTable, 'GroupMembers', UsersInGroup)
//Else you can raise an exception or do whatever you want to let the user know that the group was not found
End;
//in my case I have a table with the group names and a TMemoField with the users, so I look up the group and return a list with the users
an example of call to the wrapper function would be:
GetUsersForGroup(UsersTable, Edit1.Text, ListBox1.Items)
-------------------
'til here we can load from our database to the screen... now let's see the other way, when we need to make changes to that MemoField
//this function will do it
Procedure StringsToMemoField(Table:TTable; Const FieldName:String; NewLines:TStrings);
Begin
//all exceptions are handled outside and there's nothing to free here, so no need for a Try...Finally
If (NewLines.Count0) Then //if linecount=0 don't botter
With Table Do
Begin
Edit;
TMemoField(FieldByName(FieldName)).Assign(NewLines);
Post
End
End;
//now let's wrap it so is more useful
//In my case I used this last function to save the changes to the groups, adding or removing users
Procedure SetUsersForGroup(FromTable:TTable; Const GroupName:String; UsersInGroup:TStrings);
Begin
If (UsersInGroup.Count0) Then
With FromTable Do
If (FindKey([GroupName])) Then
Try
StringsToMemoField(FromTable, 'GroupMembers', UsersInGroup);
Except
//handle the exception as you need
End
End;
an example of call to this last one:
SetUsersForGroup(UsersTable, Edit1.Text, ListBox1.Items)
that's it for now
keep up coding
salu2
EberSys
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