ColdFusion Basics (Cont’d) ColdFusion Flow Control Constructs

1. ColdFusion Basics (Cont’d)ColdFusion Flow Control Constructs 321483

2. Using Selection to Control Flow • Selection is a flow-control concept where one or more alternatives are examined and a course of action is taken based on those alternatives • Selection construct is implemented in Coldfusion using CFIF and CFSWITCH tags • Conditions, relational, and logical operators are used with selection statements

3. Using Selection to Control Flow • Condition: • A condition is a comparison of two quantities • A condition can be either true or false • Relational Operators: • Relational operators are used to compare quantities in a condition • GT, LT, GE, LE, EQ, NEQ are the relational operators supported by ColdFusion • Logical Operators: • AND, OR, NOT are the logical operators supported by ColdFusion

4. CFIF Tag • CFIF tag used to set up a selection construct in ColdFusion • <CFIF condition>True Action<CFELSE>False Action</CFIF> • Click to view CFIF tag syntax

5. CFIF Tag

6. CFIF Tag • These tags must be used in sequence • If condition is true, True Action is executed and False Action is skipped • If condition is false, False Action is executed and True Action is skipped

7. Relational Operators

8. Relational Operators and Data Types

9. Relational Operators and Data Types • See files cfif_relop1.cfm and cfif_relop2.cfm for some examples of how to use CFIF tag and relational operators

10. Nested CFIF Tags • You can enclose CFIF tags within other CFIF tags - nested CFIF tags • Example: <CFIF Condition1> <CFIF Condition2> True action 2<CFELSE> False action 2</CFIF> <CFELSE>False action 1 </CFIF>

11. Nested CFIF Tags • The condition in the outer CFIF tag is evaluated first - then the condition with the inner CFIF tag is evaluated as necessary • See file cfif_nested.cfm for an example of nested CFIF tags

12. Combining CFELSE Tag • You can combine a CFELSE and CFIF tag by using the CFELSIF tag • Example: <CFIF Condition1> Action 1<CFELSIF Condition2> Action 2<CFELSIF Condition2> Action 3<CFELSE> Action 4 </CFIF>

13. Combining CFELSE Tag • See file cfelseif.cfm for an example of CFELSEIF tags

14. Using Logical Operators • CFIF Statements can contain more than one expression to evaluate • In this case, you must separate expressions by logical operators such as AND, OR and NOT • Logical operators let you combine simple conditions to form complex ones • See file logical_op.cfm for an example of nested logical operators use

15. Using Logical Operators (Truth) Table of And Operator Condition1 Condition2 Condition1 AND Condition 2 T T T T F F F T F F F F

16. Using Logical Operators (Truth) Table of OR Operator Condition1 Condition2 Condition1 OR Condition 2 T T T T F T F T T F F F

17. Not(Cond1AndCond2) Not(Cond1)OrNot(Cond2) = Not(Cond1OrCond2) Not(Cond1)AndNot(Cond2) = Not(=) <> = Not(<>) = = Not(<) >= = Not(<=) > = Not(>) <= = Not(>=) < = Using Logical Operators • Not Operator

18. Using Logical Operators • Not Operator - Examples • Not X < 10 • Not (X >= 10 and X < 20) • Not (X =10 or Y <> 30)

19. Logical Operator Precedence

20. Using CFSWITCH Statement • Allows you to select an action from several different actions <CFSWITCH EXPRESSION=“expression”><CFCASE VALUE=“value-list1”> Action1 </CFCASE><CFCASE VALUE=“value-list2”> Action2 </CFCASE><CFDEFAULTCASE> Action3</CFDEFAULTCASE> </CFSWITCH>

21. Using CFSWITCH Statement

22. Using CFSWITCH Statement • CFSWITCH EXPRESSION attribute can be assigned any valid expression - also called selector expression • Result is the basis for the selection of the action to be performed - Value also called selector value • CFCASE VALUE attribute used to match value of expression - if a match that case is performed • CFDEFAULTCASE tag defines default action to be performed • Click to view CFSWITCH tag syntax

23. Using CFSWITCH Statement • See file cfswitch.cfm for an example of CFSWITCH tag use

24. Using Repetition • When you need to execute a set or program statements many times - use the repetition flow control statements • ColdFusion provides the CFLOOP tag to perform repetition • Used to implement FOR, LIST, WHILE, and QUERY loops

25. Using Repetition • Use FOR loops when you know exactly how many times a set of statements should be executed • Use WHILE loops when you want to execute a set of statements as long as a condition is True • Use LIST loops when you want to execute a set of statements repeatedly • QUERY loops are discussed later

26. FOR Loops • Used to execute a set of statements a predefined number of times <CFLOOP INDEX=“for_variable”FROM=“start_value”TO=“end_value”STEP=“increment_value”>Statements to loop through</CFLOOP> • Click to view For Loop tag syntax

27. FOR Loops

28. FOR Loops • INDEX assigned name of variable that controls loop execution • FROM assigned a value or expression that provides starting loop value • TO assigned value or expression that provides ending loop value • STEP assigned to value that controls amount index variable is incremented in each loop iteration

29. LIST Loops • 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> • Click to view List Loop tag syntax

30. LIST Loops

31. LIST Loops • INDEX assigned name of variable that controls loop execution • LIST assigned a list of comma separated values - INDEX is assigned values in list one at a time as the loop executes • See file list_loop.cfm for an example of List Loops use

32. WHILE Loops • 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> • Click to view While Loop tag syntax

33. WHILE Loops

34. 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 • See file while_loop.cfm for an example of While Loops use