Changes between Initial Version and Version 1 of Try

Timestamp:

02/15/10 01:18:55 (15 years ago)

Author:

hopscc

Comment:

--

Try

@@ +1 @@
+= Try/Catch = 
+
+A statement that specifies to run (try) a block of code and to trap (catch) and handle 
+any exceptions thrown from it.
+
+Exceptions can be specified to be trapped in one of three ways
+    * catch exception type and capture the exception instance for use in its corresponding catch block.
+    * catch exception type ignoring actual instance
+    * catchAll clause - catch any exceptions not already given
+    
+The '''success''' clause is optional and if specified is executed only if no catch clauses 
+are invoked (i.e if no catch specified exceptions are thrown).
+
+The '''finally''' clause is also optional and if specified is invoked after all other 
+clauses regardless of whether any exceptions were thrown, trapped and/or rethrown.
+Control is always passed to any finally block regardless of how the try block exits.
+
+Whereas catch clauses are used to handle exceptions that occur in a statement block, 
+'''finally''' is used to guarantee a statement block of code executes regardless of how the 
+preceding try block is exited. Used for must-cleanup situations (see also [wiki:Using Using]). 
+
+
+== Grammar ==
+{{{
+try
+    BLOCK
+catch VARNAME as EXCEPTIONTYPE  (*1)   or
+catch EXCEPTIONTYPE             (*2)   or
+catch                           (*3)
+    CATCH_BLOCK
+    
+[success                         (*4)
+    SUCCESS_BLOCK ]
+
+[finally                         (*4)
+    FINALLY_BLOCK ]
+
+}}}
+    *1 - specify a variable to place the caught exception in to manipulate (or rethrow)
+    within the subsequent catch codeblock
+    
+    *2 - Use this form to catch a particular exceptionType when dont need the particular
+    exception instance. (To ignore the exception or exit for example)
+
+    *3 - Catch any and all exceptions not already specifically listed (!CatchAll clause)
+    There can be only one catchAll clause and if used it must be after all
+    other catch clauses.
+
+    *4 - optional
+
+== Platform ==
+
+== Examples ==
+{{{
+
+# parsing numbers
+s = tok.text.replace('_', '')
+if s.endsWith('f')
+    s = s[:-1]
+try
+    value = float.parse(s, Utils.cultureInfoForNumbers)
+catch FormatException
+    .recordError('Unexpected FormatException for float literal "[tok.text]".')
+catch OverflowException
+    .recordError('Range overflow for float literal "[tok.text]".')
+
+
+# reading file contents
+contents = 'test: failure'
+try
+    contents = File.readAllText('myFile.txt')
+catch ioe as IOException
+    print 'I/O Error: [ioe.message]'
+success
+    assert 'test' in contents
+    
+# customException
+try
+    if source.length==0
+        _warning('File is empty.')
+    else if source.trim.length==0
+        _warning('File is completely blank.')
+    return _parseTokens()
+catch pe as ParserException
+    if _errorRecorder, _errorRecorder.recordError(pe)
+    _tokenizer = nil
+    throw  # rethrow exception trapped above
+}}}
+
+
+== Notes ==