Using UDFs effectively
217
Generating exceptions in UDFs
If you define your function using the
cffunction
tag, you can use the
cfthrow
and
cfrethrow
tags to throw errors to the page that called the function. You can use this technique whenever
your UDF identifies an error, instead of displaying a message or returning an error status. For
example, the following code rewrites the example from
“Providing status information”
on page 214
to use the
cffunction
tag and CFML, and to throw and handle an exception if any
of the form values are not positive numbers.
The lines that identify invalid data and throw the exception are in bold. The remaining lines are
equivalent to the CFScript code in the previous example. However, the code that removes
unwanted characters must precede the error checking code.
<cffunction name="TotalInterest">
<cfargument name="principal" required="Yes">
<cfargument name="annualPercent" required="Yes">
<cfargument name="months" required="Yes">
<cfset principal = trim(principal)>
<cfset principal = REReplace(principal,"[\$,]","","ALL")>
<cfset annualPercent = Replace(annualPercent,"%","","ALL")>
<cfif ((principal LE 0) OR (annualPercent LE 0) OR (months LE 0))>
<cfthrow type="InvalidData" message="All values must be greater than 0.">
</cfif>
<cfset years = 0>
<cfset interestRate = 0>
<cfset totalInterest = 0>
<cfset interestRate = annualPercent / 100>
<cfset years = months / 12>
<cfset totalInterest = principal*
(((1+ interestRate)^years)-1)>
<cfreturn DollarFormat(totalInterest)>
</cffunction>
The code that calls the function and handles the exception looks like the following. The changed
lines are in bold.
<cftry>
<cfset status = StructNew()>
<cfset myInterest = TotalInterest(Form.Principal, Form.AnnualPercent,
Form.Months, status)>
<cfoutput>
Loan amount: #Form.Principal#<br>
Annual percentage rate: #Form.AnnualPercent#<br>
Loan duration: #Form.Months# months<br>
TOTAL INTEREST: #myInterest#<br>
</cfoutput>
<cfcatch type="InvalidData">
<cfoutput>
#cfcatch.message#<br>
</cfoutput>
</cfcatch>
</cftry>
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...