RecordLockingConflict class: Difference between revisions
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<!-- RecordLockingConflict class --> | <!-- RecordLockingConflict class --> | ||
The < | The <var>RecordLockingConflict</var> exception class catches record locking conflict errors thrown by file object operations; that is from methods in the <var>[[File_classes|file classes]]</var> (<var>[[Record_class|Record]]</var>, <var>[[Recordset_class|Recordset]]</var>, <var>[[SortedRecordset_class|SortedRecordset]]</var>, and <var>[[RecordsetCursor_class|RecordsetCursor]]</var>). | ||
record locking conflict errors thrown by file object operations | |||
methods in the file classes (Record, Recordset, SortedRecordset, RecordsetCursor). | |||
An exception is thrown only if there is a Catcher for the exception. | An exception is thrown only if there is a Catcher for the exception. | ||
There is no distinction between | There is no distinction between a Find conflict and a record locking conflict. For example, you can use the following: | ||
a Find conflict and a record locking conflict. | |||
For example, you can use the following: | |||
<p class="code"> try | <p class="code"> [[try]] | ||
fd to %foo | fd to %foo | ||
... | ... | ||
end find | end find | ||
catch recordLockingConflict | [[catch]] recordLockingConflict | ||
... | ... | ||
end try | end try | ||
| Line 20: | Line 16: | ||
And you can also use: | And you can also use: | ||
<p class="code"> try | <p class="code"> [[try]] | ||
%rec = new(%recnum, exclusive) | %rec = [[New_(Record_constructor)|new]](%recnum, exclusive) | ||
for record %rec | for record %rec | ||
... | ... | ||
end for | end for | ||
catch recordLockingConflict | [[catch]] recordLockingConflict | ||
... | ... | ||
end try | end try | ||
</p> | </p> | ||
You can even catch record locking conflicts caused by LoopLockStrength promotions | You can even [[catch]] record locking conflicts caused by <var>[[LoopLockStrength_(Record_property)|LoopLockStrength]]</var> promotions during a loop: | ||
during a loop: | |||
<p class="code"> %rec = new(%recnum, none, loopLockStrength=share) | <p class="code"> %rec = new(%recnum, none, loopLockStrength=share) | ||
... | ... | ||
try for record %rec | [[try]] for record %rec | ||
... | ... | ||
end for | end for | ||
catch recordLockingConflict | [[catch]] recordLockingConflict | ||
... | ... | ||
end try | end try | ||
| Line 45: | Line 40: | ||
<p class="code"> %curser = new(%recset, loopLockStrength=none) | <p class="code"> %curser = new(%recset, loopLockStrength=none) | ||
... | ... | ||
try | [[try]] | ||
for record at cursor %curser | for record at cursor %curser | ||
... | ... | ||
end for | end for | ||
catch recordLockingConflict | [[catch]] recordLockingConflict | ||
.. | .. | ||
end try | end try | ||
| Line 59: | Line 54: | ||
end find | end find | ||
... | ... | ||
try for each record in %recset | [[try]] for each record in %recset | ||
... | ... | ||
end for | end for | ||
catch recordLockingConflict | [[catch]] recordLockingConflict | ||
... | ... | ||
end try | end try | ||
</p> | </p> | ||
In the latter example, note that any iteration of the For loop can throw | In the latter example, note that any iteration of the For loop can <var>throw</var> an exception, and there is no way of picking up where you left off (at the next record, say) if you get a <var>RecordLockingConflict</var> exception in such a case. So, unless you always want to lose the whole loop on a record locking conflict, such a case is almost always better structured with a cursor on the recordset and with <var>Try</var> around the <var>For Record At Cursor</var> loop: | ||
an exception, and there is no way of picking up where you left off | |||
(at the next record, say) if you get a RecordLockingConflict exception in | |||
such a case. | |||
So, unless you always want to lose the whole loop | |||
on a record locking conflict, such a case is almost always better structured | |||
with a cursor on the recordset and with Try around the For Record At Cursor loop: | |||
<p class="code"> fdwol to %recset = new(loopLockStrength=exclusive) | <p class="code"> fdwol to %recset = new(loopLockStrength=exclusive) | ||
... | ... | ||
| Line 80: | Line 69: | ||
%curser = new(%recset, loopLockStrength=exclusive) | %curser = new(%recset, loopLockStrength=exclusive) | ||
repeat while %curser:state eq hasRecord | repeat while %curser:state eq hasRecord | ||
try for record at cursor %curser | [[try]] for record at cursor %curser | ||
... | ... | ||
end for | end for | ||
catch recordLockingConflict | [[catch]] recordLockingConflict | ||
... | ... | ||
end try | end try | ||
%curser:next | %curser:[[next]] | ||
end repeat | end repeat | ||
</p> | </p> | ||
Note that the For statement can be on the same line as the Try, | <b><i>Note:</i></b> that the For statement can be on the same line as the <var>Try</var>, or it can be inside the <var>Try</var> block. | ||
or it can be inside the Try block. | |||
The methods in this class are listed at "[[List of RecordLockingConflict methods]]". | The methods in this class are listed at "[[List of RecordLockingConflict methods]]". | ||
[[Category:System exception classes]] | [[Category:System exception classes]] | ||
Revision as of 07:33, 22 April 2011
The RecordLockingConflict exception class catches record locking conflict errors thrown by file object operations; that is from methods in the file classes (Record, Recordset, SortedRecordset, and RecordsetCursor).
An exception is thrown only if there is a Catcher for the exception.
There is no distinction between a Find conflict and a record locking conflict. For example, you can use the following:
try fd to %foo ... end find catch recordLockingConflict ... end try
And you can also use:
try %rec = new(%recnum, exclusive) for record %rec ... end for catch recordLockingConflict ... end try
You can even catch record locking conflicts caused by LoopLockStrength promotions during a loop:
%rec = new(%recnum, none, loopLockStrength=share) ... try for record %rec ... end for catch recordLockingConflict ... end try
Or as in the following:
%curser = new(%recset, loopLockStrength=none) ... try for record at cursor %curser ... end for catch recordLockingConflict .. end try
Or as in this example:
fdwol to %recset = new(loopLockStrength=exclusive) ... end find ... try for each record in %recset ... end for catch recordLockingConflict ... end try
In the latter example, note that any iteration of the For loop can throw an exception, and there is no way of picking up where you left off (at the next record, say) if you get a RecordLockingConflict exception in such a case. So, unless you always want to lose the whole loop on a record locking conflict, such a case is almost always better structured with a cursor on the recordset and with Try around the For Record At Cursor loop:
fdwol to %recset = new(loopLockStrength=exclusive) ... end find ... %curser = new(%recset, loopLockStrength=exclusive) repeat while %curser:state eq hasRecord try for record at cursor %curser ... end for catch recordLockingConflict ... end try %curser:next end repeat
Note: that the For statement can be on the same line as the Try, or it can be inside the Try block.
The methods in this class are listed at "List of RecordLockingConflict methods".