Loops in CF Michael Smith President TeraTech, Inc ColdFusion, Database & VB custom development

Introduction n Loops - many types n Many uses

Loop Types Here is what we will be covering:  For Loops  While Loops  Query Loops  List Loops More advanced loops not covered:  Structure Loops  COM Loops

What to use loops for n Use FOR loops when you know exactly how many times a set of statements should be executed n Use LIST loops when you want to loop over something other than numbers n Use WHILE loops when you want to execute a set of statements as long as a condition is True n Use QUERY loops when you want to repeat for all records in a query.

Loop uses n Repeating HTML n Processing text n Outputing queries n Nested Loops n Breaking out of loops n Banding report lines

1.1 FOR Loops n “FOR NEXT” loop <CFLOOP INDEX="parameter_name" FROM="beginning_value" TO="ending_value" STEP="increment"> Lines to repeat Is INDEX LT TO? If so loop again INDEX = FROM INDEX = INDEX + STEP

FOR CFLOOP Parameters n INDEX -name of variable that controls loop execution n FROM - starting loop value n TO - ending loop value n STEP – controls amount index variable is incremented (or decremented) in each loop iteration n Note: Loop may execute zero times if backwards - for example FROM 2 TO 1

FOR Loop Example 1 The loop index is #LoopCount#. (Assume inside CFOUTPUT tags) This produces…. The loop index is 5. The loop index is 4. The loop index is 3. The loop index is 2. The loop index is 1.

FOR Loop Example 2 HTML list boxes of hours that goes from 0 to 23 #hour#

Nested Loop Example List box with all the hours and minutes of the day. #hour#:#minute# That is 1440 items! Not a good idea for a real site

1.2 WHILE Loops n “DO WHILE” loop Is condition true? If so loop again

WHILE Loop details n FOR and LIST loops are executed a certain number of times n WHILE loops are executed while a condition is true Statements to loop through

WHILE Loop Parameters n WHILE Loops n CONDITION contains a logical expression that is evaluated before each loop iteration n As long as CONDITION is true – the loop is executed n Tip - Make sure you change the values of variables used in CONDITION expression in the loop body – otherwise infinite loop!

Conditional operators n GT, LT, GTE, LTE, EQ, NEQ, IS, CONTAINS are the relational operators supported by ColdFusion n (don’t use > etc because CFML uses >) n AND, OR, NOT are the logical operators supported by ColdFusion n Use ()s to group expressions

Operator precedence () IS, EQ, NEQ, LT, LE, GT, GE, CONTAINS NOT AND OR

CFBREAK n CFBREAK exits the current loop More code here

1.3 Query Loops n CFOUTPUT n CFLOOP n CFMAIL

CFOUTPUT Query Loop SELECT FROM Customer #Get . # Variable available:  Queryname.currentrow  Queryname.recordcount Any records left? If so loop again Start at first record

CFLOOP Query Loop SELECT FROM Customer #Get . # Any records left? If so loop again Start at first record

CFMAIL loop Send one for each record in the query SELECT FROM Customer <CFMAIL QUERY="Get " TO="#Get . #" SUBJECT=“Test” SERVER="smtp.mycompany.com"> Hi There Any records left? If so loop again Start at first record

Nested Query Loop Example SELECT , SecurityLevel FROM Customer SELECT Text, Subject FROM Messages WHERE SecurityLevel = #Get .SecurityLevel# <CFMAIL QUERY="GetText" TO="#Get . #" SUBJECT="#GetText. Subject#" SERVER="smtp.mycompany.com">#GetText. Text#

Other recordsets n You can loop over record sets from other tags than CFQUERY: n CFDIRECTORY – file list n CFPOP – read n CFSEARCH – Verity text search n CFLDAP – LDAP records n CFWDDX

1.4 List Loops n “FOR EACH” loop <CFLOOP INDEX="ListElement" LIST="#form.state#" DELIMITERS=","> #ListElement# u Other delimiters than comma are allowed Any items left in list? If so loop again Start at first item in list

How list loops work n LIST loops allow you to list the values for the control variable instead of computing them as in the FOR loop <CFLOOP INDEX=“list_variable” LIST=“value_list”> Statements to loop through

List Loop parameters n INDEX - variable that controls loop execution n LIST - a list of comma separated values n INDEX is assigned the values in list one at a time as the loop executes n DELIMITERS – optional to give a delimiter other than comma

List Loop example n List local states <CFLOOP INDEX=“StateName” LIST=“MD, VA, DC”> #StateName# Produces…. MD VA DC

Text file as a “list” n Text file processing by line can be done using lists n Read in text file using CFFILE n Use CR LF as delimiter n The list elements are now the lines in the file.

1.5 Structure Loops n Loop over all people in the Department #person#, #StructFind(Departments, person#) Any items left in structure? If so loop again Start at first item in structure

1.6 COM Loops n FOR EACH OBJECT Loops #file2.name#

CFSCRIPT Loops n CFScript is a JavaScript like language that provides the standard looping features of CFML plus a few more looping features n For n While n Do-while n For-in CFScript also includes the continue and break statements that control loop processing.

CFSCRIPT Loops syntax n FOR loop for (inital-expression; test- expression; final-expression) statement n WHILE loop while (expression) statement n UNTIL loop – evaluates condition at end of loop do statement while (expression);

More CFSCRIPT loops n Structure loop for (variable in structure) statement n The continue statement tells ColdFusion to skip to the beginning of the next loop iteration. n The break statement exits the current loop or case statement. Similar to n Note: Still use LE etc for conditionals in CFSCRIPT and not the JavaScript <

CFSCRIPT for n for (inital-expression; test-expression; final-expression) statement n Evaluates the initial expression. n Evaluates the test-expression. n If the test-expression is False, exits the loop and processing continues following the statement.If the test-expression is True: u Executes the statement (or statement block). u Evaluates the final-expression. u Loops statement can be a single semicolon terminated statement or a statement block in curly braces.

for loop example n Assign array a(1) =1 etc for(index=1; index LT 10; index = index + 1) a[index]=index;

Infinite for loop example n Search for key using break to stop infinite loop 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; } }

Resources n CFDOCS n Ben Forta Books n md.org/articles/introCF-4-Lists.cfm n

Questions n