
204
Chapter 10: Writing and Calling User-Defined Functions
Using arguments
Function arguments can have the same names, but different values, as variables in the caller.
Avoid such uses for clarity, however.
The following rules apply to argument persistence:
•
Because simple variable and array arguments are passed by value, their names and values exist
only while the function executes.
•
Because structures, queries, and objects such as COM objects are passed by reference, the
argument
name
exists only while the function executes, but the underlying
data
persists after
the function returns and can be accessed by using the caller’s variable name. The caller’s
variable name and the argument name can, and should, be different.
Note:
If a function must use a variable from another scope that has the same name as a function-only
variable, prefix the external variable with its scope identifier, such as Variables or Form. (However,
remember that using variables from other scopes directly in your code is often poor practice.)
A User-defined function example
The following simple function takes a principal amount, an annual percentage rate, and a loan
duration in months and returns the total amount of interest to be paid over the period. You can
optionally use the percent sign for the percentage rate, and include the dollar sign and comma
separators for the principal amount.
You could use the
TotalInterest
function in a
cfoutput
tag of a form’s action page, as follows:
<cfoutput>
Loan amount: #Form.Principal#<br>
Annual percentage rate: #Form.AnnualPercent#<br>
Loan duration: #Form.Months# months<br>
TOTAL INTEREST: #TotalInterest(Form.Principal, Form.AnnualPercent,
Form.Months)#<br>
</cfoutput>
Defining the function using CFScript
<cfscript>
function TotalInterest(principal, annualPercent, months) {
Var years = 0;
Var interestRate = 0;
Var totalInterest = 0;
principal = trim(principal);
principal = REReplace(principal,"[\$,]","","ALL");
annualPercent = Replace(annualPercent,"%","","ALL");
interestRate = annualPercent / 100;
years = months / 12;
totalInterest = principal*(((1+ interestRate)^years)-1);
Return DollarFormat(totalInterest);
}
</cfscript>
Содержание ColdFusion MX
Страница 1: ...Developing ColdFusion MX Applications...
Страница 22: ...22 Contents...
Страница 38: ......
Страница 52: ...52 Chapter 2 Elements of CFML...
Страница 162: ......
Страница 218: ...218 Chapter 10 Writing and Calling User Defined Functions...
Страница 250: ...250 Chapter 11 Building and Using ColdFusion Components...
Страница 264: ...264 Chapter 12 Building Custom CFXAPI Tags...
Страница 266: ......
Страница 314: ...314 Chapter 14 Handling Errors...
Страница 344: ...344 Chapter 15 Using Persistent Data and Locking...
Страница 349: ...About user security 349...
Страница 357: ...Security scenarios 357...
Страница 370: ...370 Chapter 16 Securing Applications...
Страница 388: ...388 Chapter 17 Developing Globalized Applications...
Страница 408: ...408 Chapter 18 Debugging and Troubleshooting Applications...
Страница 410: ......
Страница 426: ...426 Chapter 19 Introduction to Databases and SQL...
Страница 476: ...476 Chapter 22 Using Query of Queries...
Страница 534: ...534 Chapter 24 Building a Search Interface...
Страница 556: ...556 Chapter 25 Using Verity Search Expressions...
Страница 558: ......
Страница 582: ...582 Chapter 26 Retrieving and Formatting Data...
Страница 668: ......
Страница 734: ...734 Chapter 32 Using Web Services...
Страница 760: ...760 Chapter 33 Integrating J2EE and Java Elements in CFML Applications...
Страница 786: ...786 Chapter 34 Integrating COM and CORBA Objects in CFML Applications...
Страница 788: ......
Страница 806: ...806 Chapter 35 Sending and Receiving E Mail...