[Inland]
http://delphi.ktop.com.tw/topic.asp?topic_id=53541
Shinhrn Tryadoconnection1.begintrans;
// Data processing
Adoconnection1.committrans; Exceptadoconnection1.rollbackTrans; showMessage ('archive failed!');
If an error occurs, RollBackTrans can be executed to cancel all anime action in all data processing, such as (write, delete, etc.) ....
The BigDogchina try statement is an auxiliary process to control the execution of the program, often uses Abort, EXIT, etc. Let's take a look at this:
Procedure TFORM1.BUTTON1CLICK (Sender: TOBJECT);
Begin
Try
if True Then
Abort;
Except // Abort excitation exception is captured, so the exception code in ExcePt ... End is executed CODE
SHOWMESSAGE ('Abort');
END;
ShowMessage ('Processing!'); // Execution, because the exception has been processed, if you use try ... finally, the sentence will not be processed
END;
Note: If Abort is included in a Try ... Except, only Tr ... Except is exited, then execute the ExcePt ... End block, and finally the following statement is continued. If included in the Try ... finally block, execute the Finally ... End block and then exit the process
Let's take a look at it and exit looks.
Procedure tfrom1.button2click (sender: TOBJECT);
Begin
Try
if True Then
EXIT;
Finally
ShowMessage ('Abort'); //
END;
ShowMessage ('handling "); // does not execute
END;
Here is the use of try ... finally, you can also match it.
HLT and
RUNERROR
And Try often uses Continu and Break, let's take a look:
Procedure TFORM1.BUTTON3CLICK (Sender: tojbect);
VAR
I: integer;
Begin
For i: = 0 to 2 do
Begin
Try
IF i <2 THEN
Continue; // Please note that continchee is here
ShowMessage (INTSTR (i));
Finally
ShowMessage ('This is Finally!');
END;
END;
END;
Continue If located in the Try ... finally block, you will first perform Finally ... END and then enter the next loop. The above example execution result is: first display two times' this is finaly! '(Corresponding to i = 0 and 1), then display once I (corresponding i = 2), and finally display a time I (or corresponding i = 2).
But Break's usage is not quite the same, if it is in the Try ... finally block, Finally ... End block will also be executed, see below:
Procedure TFORM1.BUTTON4CLICK (Sender: TOBJECT);
VAR
I: integer;
Begin
For i: = 0 to 2 do
Begin
Try
IF I> 0 THEN
Break;
ShowMessage (INTSTR (i)); Finally
ShowMessage ('This is in Finally');
END;
END;
END;
In summary, you can see Try ... End ... End and Try ... Finally ... End and Abort, Exit, Halt, RuNerror, Continue, Break usage! Thank you
