Adobe 38043740 Developing Applications - Page 122

DEVELOPING COLDFUSION 9 APPLICATIONS 117 The CFML Programming Language • Empty Note: The test expression is re-evaluated before each repeat of the loop. If code inside the loop changes any part of the test expression, it can affect the number of iterations in the loop. The statement can be a single semicolon terminated statement or a statement block in curly brackets. When ColdFusion executes a for loop, it does the following: 1 Evaluates the initial expression. 2 Evaluates the test-expression. 3 If the test-expression is False, exits the loop and processing continues following the statement. If the test-expression is True: a Executes the statement (or statement block). b Evaluates the final-expression. c Returns to Step 2. For loops are most commonly used for processing in which an index variable is incremented each time through the loop, but it is not limited to this use. The following simple for loop sets each element in a 10-element array with its index number. for(index=1; index LTE 10; index = index + 1) a[index]=index; The following, more complex, example demonstrates two features: • The use of curly brackets to group multiple statements into a single block. • An empty condition statement. All loop control logic is in the statement block. strings=ArrayNew(1); ArraySet(strings, 1, 10, "lock"); strings[5]="key"; indx=0; for( ; ; ) { indx=indx+1; if(Find("key",strings[indx],1)) { WriteOutput("Found key at " & indx & "."); break; } else if (indx IS ArrayLen(strings)) { WriteOutput("Exited at " & indx & "."); break; } } This example shows one important issue that you must remember when creating loops: always ensure that the loop ends. If this example lacked the elseif statement, and there was no "key" in the array, ColdFusion would loop forever or until a system error occurred; you would have to stop the server to end the loop. Last updated 1/20/2012