Loops in CF

1
Loops in CF

• Sandra Clark
• Senior Software Developer
• Constella Group
• sclark_at_constellagroup.com

2
Introduction

• Loops - many types
• Many uses

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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

4
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
• ltCFLOOP INDEX"parameter_name"
• FROM"beginning_value"
• TO"ending_value"
• STEP"increment"gt
• Lines to repeat
• lt/CFLOOPgt

INDEX FROM
Is INDEX LT TO? If so loop
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
Must have CFOUTPUT

• ltCFLOOP INDEX"LoopCount" FROM"5" TO"1"
  STEP"-1"gt ltCFOUTPUTgt
• The loop index is LoopCount.ltBRgt lt/CFOUTPUTgt
• lt/CFLOOPgt
• (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
• ltSELECT NAME"Hour"gt
• ltCFLOOP INDEX"hour" FROM"0" TO"23"gt
•    ltCFOUTPUTgt
•     ltOPTION VALUE"hour"gthour
•   lt/CFOUTPUTgt
• lt/CFLOOPgt
• lt/SELECTgt

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Nested Loop Example
This is 1440 items! Not a good idea for a real
site

• List box with all the hours and minutes of the
  day.  
• ltSELECT NAME"HourAndMinutes"gt
• ltCFLOOP INDEX"hour" FROM"0" TO"23"gt
•   ltCFLOOP INDEX"minute" FROM"0" TO"59"gt
•     ltCFOUTPUTgt
•     ltOPTION VALUE"'hourminute'"gthourminu
  te
•     lt/CFOUTPUTgt
•   lt/CFLOOPgt
• lt/CFLOOPgt
• lt/SELECTgt

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1.2 WHILE Loops
Same syntax as CFIF conditions

• DO WHILE loop
• ltCFSET Dice 0gt
• ltCFLOOP CONDITION"Dice LTE 5"gt
• ltCFSET Dice RandRange(1,6)gt
• ltCFOUTPUTgtdicelt/CFOUTPUTgt
• ltBRgt
• lt/CFLOOPgt

Is condition true? If so loop again
Final loop run has condition false!
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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
• ltCFLOOP CONDITIONwhile-conditiongt
• Statements to loop through
• lt/CFLOOPgt

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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
• (dont use gt etc because CFML uses gt)
• 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, CONTAINS
• NOT
• AND
• OR

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CFBREAK

• CFBREAK exits the current loop
• ltCFSET StopIt 0gt
• ltCFLOOP CONDITIONTRUEgt
• ltCFSET StopIt RandRange(1,10)gt
• ltCFIF StopIt LTE 5gt
• ltCFBREAKgt
• lt/CFIFgt
• ltCFOUTPUTgtStopItlt/CFOUTPUTgtltBRgt
• lt/CFLOOPgt
• More code here

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1.3 Query Loops

• CFOUTPUT
• CFLOOP
• CFMAIL

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CFOUTPUT Query Loop

• ltCFQUERY NAME"GetEmail"   DATASOURCE"Library"gt
•    SELECT Email FROM Customer
• lt/CFQUERYgt
• ltCFOUTPUT QUERY"GetEmail"gt
• GetEmail.EmailltBRgt
• lt/CFOUTPUTgt
• Variable available
• Queryname.currentrow
• Queryname.recordcount

Start at first record
Any records left? If so loop again
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CFLOOP Query Loop

• ltCFQUERY NAME"GetEmail"   DATASOURCE"Library"gt
•    SELECT Email FROM Customer
• lt/CFQUERYgt
• ltCFLOOP QUERY"GetEmail"gt
• ltCFOUTPUTgtGetEmail.EmailltBRgtlt/CFOUTPUTgt
• lt/CFLOOPgt

Start at first record
CFOUTPUT required
Any records left? If so loop again
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CFMAIL loop

•  Send one email for each record in the query 
• ltCFQUERY NAME"GetEmail"   DATASOURCE"Library"gt
•    SELECT Email FROM Customer
• lt/CFQUERYgt
• ltCFMAIL QUERY"GetEmail"
•       TO"GetEmail.Email"
•       FROM"info_at_mycompany.com"
•       SUBJECTTest
•       SERVER"smtp.mycompany.com"gt
• Hi There
•    lt/CFMAILgt

Start at first record
Any records left? If so loop again
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Nested Query Loop Example

• ltCFQUERY NAME"GetEmail"   DATASOURCE"Library"gt
•    SELECT Email , SecurityLevel  FROM Customer
• lt/CFQUERYgt
• ltCFLOOP QUERY"GetEmail"gt
•    ltCFQUERY NAME"GetText" DATASOURCE"Library"gt
•       SELECT EmailText, EmailSubject FROM
  Messages
•       WHERE  SecurityLevel GetEmail.SecurityLev
  el
•    lt/CFQUERYgt
•     ltCFMAIL QUERY"GetText"
•       TO"GetEmail.Email"
•       FROM"info_at_mycompany.com"
•       SUBJECT"GetText.EmailSubject"
•       SERVER"smtp.mycompany.com"gtGetText.EmailTe
  xt
•    lt/CFMAILgt
• lt/CFLOOPgt

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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
• ltCFLOOP INDEX"ListElement"
• LIST"form.state"
• DELIMITERS","gt
• ltCFOUTPUTgtListElement
• lt/CFOUTPUTgtltBRgt
• lt/CFLOOPgt
• Other delimiters than comma are allowed

Start at first item in list
Any items left in list? If so loop again
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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
• ltCFLOOP INDEXlist_variable
• LISTvalue_listgt
• Statements to loop through
• lt/CFLOOPgt

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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
• ltCFLOOP INDEXStateName
• LISTMD, VA, DCgt
• ltCFOUTPUTgtStateName
• lt/CFOUTPUTgtltBRgt
• lt/CFLOOPgt
• Produces.

MD VA DC
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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 as delimiter
• The list elements are now the lines in the file.

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Read text file code

• ltcffile action"READ" file"C\afile.txt"
  variable"text_file"gt
• ltCFLOOP list"text_file" index"line"
  delimiters"CHR(13)"gt
• ltcfoutputgtlineltbrgtlt/cfoutputgt
• lt/CFLOOPgt
• ltCFOUTPUTgtCount lines is
• ListLen(text_file,"CHR(13)") lt/CFOUTPUTgt

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1.5 Structure Loops

• Loop over all people in the Department
• ltCFLOOP COLLECTIONDepartments ITEM"person"gt
• person,
• StructFind(Departments, person)
• lt/CFLOOPgt

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
• ltCFLOOP COLLECTIONFFUNC ITEMfile2gt
• ltCFOUTPUTgt file2.name ltBRgt lt/CFOUTPUTgt
• lt/CFLOOPgt

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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 loop
• for (inital-expression test-expression
  final-expression) statement
• WHILE loop
• while (expression) statement
• UNTIL loop evaluates condition at end of loop
• do statement while (expression)

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More CFSCRIPT loops

• Structure loop
• for (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 ltCFBREAKgt
• Note Still use LTE etc for conditionals in
  CFSCRIPT and not the JavaScript lt

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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

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for loop example

• Assign array a(1) 1 etc
• for(index1 index LT 10 index index 1)
  aindexindex

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Infinite for loop example

• Search for key using break to stop infinite loop
• indx0
• for( )
• indxindx1 if(Find("key",stringsindx,1))
  WriteOutput("Found key at " indx ".ltbrgt")
  break
• else if (indx IS ArrayLen(strings))
  WriteOutput("Exited at " indx ".ltbrgt")
  break

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Resources

• CFDOCS
• Ben Forta Books
• http//www.cfug-md.org/articles/introCF-4-Lists.cf
  m
• http//www.houseoffusion.com

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Questions

• sclark_at_constellagroup.com