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

Loops in CFMichael Smith

President

TeraTech, Inc

ColdFusion, Database & VB custom development

http://www.teratech.com

800-447-9120

www.teratech.com

Introduction Loops - many types Many uses

The Challenge

SecuritySecurity

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Loop TypesHere is what we will be covering:

For Loops While Loops Query Loops List Loops

More advanced loops not covered: Structure Loops COM Loops

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What to use loops for

Use FOR loops when you know exactly how many times a set of statements should be executed

Use LIST loops when you want to loop over something other than numbers

Use WHILE loops when you want to execute a set of statements as long as a condition is True

Use QUERY loops when you want to repeat for all records in a query.

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Loop uses

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

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1.1 FOR Loops “FOR NEXT” loop

<CFLOOP INDEX="parameter_name"

FROM="beginning_value"TO="ending_value"

STEP="increment">Lines to repeat</CFLOOP>

Is INDEX LT TO? If so loop

again

INDEX = FROM

INDEX = INDEX + STEP

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FOR CFLOOP Parameters

INDEX -name of variable that controls loop execution

FROM - starting loop value TO - ending loop value STEP – controls amount index

variable is incremented (or decremented) in each loop iteration

Note: Loop may execute zero times if backwards - for example FROM 2 TO 1

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FOR Loop Example 1

<CFLOOP INDEX="LoopCount" FROM="5" TO="1" STEP="-1">

The loop index is #LoopCount#.<BR> </CFLOOP>(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.

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FOR Loop Example 2

HTML list boxes of hours that goes from 0 to 23

<SELECT NAME="Hour"><CFLOOP INDEX="hour" FROM="0"

TO="23">   <CFOUTPUT>    <OPTION

VALUE="#hour#">#hour#  </CFOUTPUT></CFLOOP></SELECT>

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Nested Loop Example

List box with all the hours and minutes of the day.  

<SELECT NAME="HourAndMinutes"><CFLOOP INDEX="hour" FROM="0" TO="23">  <CFLOOP INDEX="minute" FROM="0"

TO="59">     <CFOUTPUT>    <OPTION

VALUE="'#hour#:#minute#'">#hour#:#minute#

    </CFOUTPUT>  </CFLOOP></CFLOOP></SELECT>

That is 1440

items! Not a

good idea for a real

site

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1.2 WHILE Loops “DO WHILE” loop

<CFSET StopIt = 0><CFLOOP CONDITION="StopIt LTE 5">

<CFSET StopIt = RandRange(1,10)>

<HR></CFLOOP>

Is condition true? If so loop again

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WHILE Loop details

FOR and LIST loops are executed a certain number of times

WHILE loops are executed while a condition is true

<CFLOOP CONDITION=“while-condition”>

Statements to loop through

</CFLOOP>

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WHILE Loop Parameters

WHILE Loops CONDITION contains a logical

expression that is evaluated before each loop iteration

As long as CONDITION is true – the loop is executed

Tip - Make sure you change the values of variables used in CONDITION expression in the loop body – otherwise infinite loop!

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Conditional operators

GT, LT, GTE, LTE, EQ, NEQ, IS, CONTAINS are the relational operators supported by ColdFusion

(don’t use > etc because CFML uses >)

AND, OR, NOT are the logical operators supported by ColdFusion

Use ()s to group expressions

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Operator precedence

()IS, EQ, NEQ, LT, LE, GT, GE,

CONTAINSNOT ANDOR

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CFBREAK

CFBREAK exits the current loop<CFSET StopIt = 0><CFLOOP CONDITION=“TRUE”> <CFSET StopIt = RandRange(1,10)>

<CFIF StopIt LTE 5><CFBREAK>

</CFIF> <CFOUTPUT></CFOUTPUT><HR></CFLOOP>More code here

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1.3 Query Loops CFOUTPUT CFLOOP CFMAIL

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CFOUTPUT Query Loop

<CFQUERY NAME="GetEmail"   DATASOURCE="Library">

   SELECT Email FROM Customer </CFQUERY>

<CFOUTPUT QUERY="GetEmail"> #GetEmail.Email#<BR></CFOUTPUT> Variable available:

Queryname.currentrow Queryname.recordcount

Any records left? If so loop again

Start at first record

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CFLOOP Query Loop

<CFQUERY NAME="GetEmail"   DATASOURCE="Library">

   SELECT Email FROM Customer </CFQUERY>

<CFLOOP QUERY="GetEmail"> <CFOUTPUT>#GetEmail.Email#<BR></

CFOUTPUT></CFLOOP>Any records

left? If so loop again

Start at first record

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CFMAIL loop  Send one email for each record in the

query <CFQUERY NAME="GetEmail"  

DATASOURCE="Library">    SELECT Email FROM Customer </CFQUERY>

<CFMAIL QUERY="GetEmail"      TO="#GetEmail.Email#"      FROM="info@mycompany.com"      SUBJECT=“Test”      SERVER="smtp.mycompany.com">Hi There   </CFMAIL>

Any records left? If so loop again

Start at first record

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Nested Query Loop Example<CFQUERY NAME="GetEmail"   DATASOURCE="Library">    SELECT Email , SecurityLevel  FROM Customer </CFQUERY> <CFLOOP QUERY="GetEmail">    <CFQUERY NAME="GetText" DATASOURCE="Library">       SELECT EmailText, EmailSubject FROM Messages       WHERE  SecurityLevel = #GetEmail.SecurityLevel#   </CFQUERY>     <CFMAIL QUERY="GetText"      TO="#GetEmail.Email#"      FROM="info@mycompany.com"      SUBJECT="#GetText.EmailSubject#"      SERVER="smtp.mycompany.com">#GetText.EmailText#   </CFMAIL></CFLOOP>

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Other recordsets

You can loop over record sets from other tags than CFQUERY:

CFDIRECTORY – file list CFPOP – read email CFSEARCH – Verity text search CFLDAP – LDAP records CFWDDX

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1.4 List Loops “FOR EACH” loop

<CFLOOP INDEX="ListElement" LIST="#form.state#" DELIMITERS=","> <CFOUTPUT>#ListElement#</CFOUTPUT><BR>

</CFLOOP> Other delimiters than comma are

allowed

Any items left in list? If so loop again

Start at first item in list

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How list loops work

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

</CFLOOP>

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List Loop parameters

INDEX - variable that controls loop execution

LIST - a list of comma separated values

INDEX is assigned the values in list one at a time as the loop executes

DELIMITERS – optional to give a delimiter other than comma

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List Loop example

List local states

<CFLOOP INDEX=“StateName”

LIST=“MD, VA, DC”>

<CFOUTPUT>#StateName#

</CFOUTPUT><BR>

</CFLOOP>

Produces…. MDVADC

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Text file as a “list”

Text file processing by line can be done using lists

Read in text file using CFFILE Use CR LF as delimiter The list elements are now the lines

in the file.

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1.5 Structure Loops Loop over all people in the

Department<CFLOOP

COLLECTION=#Departments# ITEM="person">

#person#,

#StructFind(Departments, person#)

</CFLOOP>

Any items left in

structure? If so loop again

Start at first item in

structure

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1.6 COM Loops FOR EACH OBJECT Loops<CFLOOP COLLECTION=#FFUNC#

ITEM=file2>

<CFOUTPUT> #file2.name# <BR> </CFOUTPUT>

</CFLOOP>

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CFSCRIPT Loops

CFScript is a JavaScript like language that provides the standard looping features of CFML plus a few more looping features

For While Do-while For-in CFScript also includes the continue and

break statements that control loop processing.

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CFSCRIPT Loops syntax

FOR loopfor (inital-expression; test-

expression; final-expression) statement

WHILE loopwhile (expression) statement UNTIL loop – evaluates condition at

end of loopdo statement while (expression);

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More CFSCRIPT loops

Structure loopfor (variable in structure)

statement The continue statement tells

ColdFusion to skip to the beginning of the next loop iteration.

The break statement exits the current loop or case statement. Similar to <CFBREAK>

Note: Still use LE etc for conditionals in CFSCRIPT and not the JavaScript <

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CFSCRIPT for

for (inital-expression; test-expression; final-expression) statement

Evaluates the initial expression. Evaluates the test-expression. If the test-expression is False, exits the

loop and processing continues following the statement.If the test-expression is True: Executes the statement (or statement

block). Evaluates the final-expression. Loops

statement can be a single semicolon terminated statement or a statement block in curly braces.

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for loop example

Assign array a(1) =1 etcfor(index=1; index LT 10; index

= index + 1) a[index]=index;

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Infinite for loop example

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 & ".<br>"); break; }

else if (indx IS ArrayLen(strings)) { WriteOutput("Exited at " & indx & ".<br>"); break; }

}

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Resources CFDOCS Ben Forta Books http://www.cfug-md.org/articles/

introCF-4-Lists.cfm http://www.houseoffusion.com

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Questions

michael@teratech.com