Try: what changed
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Title: Try
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| 1 | + | Back to [[Reserved words]]. | |
| 2 | + | ||
| 3 | + | The [[Reserved word|reserved word]] `try` is part of either a `try`..[[Finally|finally]] [[Block|block]] or a `try`..[[Except|except]] block. | |
| 4 | + | ||
| 5 | + | If an [[Exceptions|exception]] occurs while executing the code between `try` and `finally`, execution resumes at `finally`. If no exception occurs, the code between `finally` and [[End|end]] will be executed also. | |
| 6 | + | ||
| 7 | + | ``` pascal | |
| 8 | + | try | |
| 9 | + | // code that might generate an exception | |
| 10 | + | finally | |
| 11 | + | // will always be executed as last statements | |
| 12 | + | end; | |
| 13 | + | ``` | |
| 14 | + | ||
| 15 | + | Whenever an exception occurs, the code between `except` and `end` will be executed. | |
| 16 | + | ||
| 17 | + | ``` pascal | |
| 18 | + | try | |
| 19 | + | // code that might generate an exception | |
| 20 | + | except | |
| 21 | + | // will only be executed in case of an exception | |
| 22 | + | on E: EDatabaseError do | |
| 23 | + | ShowMessage( 'Database error: '+ E.ClassName + #13#10 + E.Message ); | |
| 24 | + | on E: Exception do | |
| 25 | + | ShowMessage( 'Error: '+ E.ClassName + #13#10 + E.Message ); | |
| 26 | + | end; | |
| 27 | + | ``` | |
| 28 | + | ||
| 29 | + | To handle exceptions with an `except` block **and** also run a `finally` block, nest one `try` block in another. | |
| 30 | + | ||
| 31 | + | ``` pascal | |
| 32 | + | try | |
| 33 | + | try | |
| 34 | + | // code dealing with database that might generate an exception | |
| 35 | + | except | |
| 36 | + | // will only be executed in case of an exception | |
| 37 | + | on E: EDatabaseError do | |
| 38 | + | ShowMessage( 'Database error: '+ E.ClassName + #13#10 + E.Message ); | |
| 39 | + | on E: Exception do | |
| 40 | + | ShowMessage( 'Error: '+ E.ClassName + #13#10 + E.Message ); | |
| 41 | + | end; | |
| 42 | + | finally | |
| 43 | + | // clean up database-related resources | |
| 44 | + | end; | |
| 45 | + | ``` | |
| 46 | + | ||
| 47 | + | ## See also | |
| 48 | + | ||
| 49 | + | - [[Raise]] | |
| 50 | + | - [[On]] | |
| 51 | + | - [[Exceptions]] | |
| 52 | + | ||
| 53 | + | --- | |
| 54 | + | *From the Free Pascal wiki, page "Try", as it stood on 2022-08-06 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).* |