56
Chapter 3: Using ColdFusion Variables
Data type notes
Although ColdFusion variables do not have types, it is often convenient to use “variable type” as a
shorthand for the type of data that the variable represents.
ColdFusion can validate the type of data contained in form fields and query parameters. For more
information, see
Chapter 26, “Validating form field data types,” on page 579
and
Chapter 20,
“Using cfqueryparam,” on page 435
.
The
cfdump
tag displays the entire contents of a variable, including ColdFusion complex data
structures. It is an excellent tool for debugging complex data and the code that handles it.
ColdFusion provides the following functions for identifying the data type of a variable:
•
IsArray
•
IsBinary
•
IsBoolean
•
IsObject
•
IsQuery
•
IsSimpleValue
•
IsStruct
•
IsXmlDoc
ColdFusion also includes the following functions for determining whether a string can be
represented as another simple data type:
•
IsDate
•
IsNumeric
ColdFusion does not use a null data type. However, if ColdFusion receives a null value from an
external source such as a database, a Java object, or some other mechanism, it maintains the null
value until you use it as a simple value. At that time, ColdFusion converts the null to an empty
string ("").
Numbers
ColdFusion supports integers and real numbers. You can intermix integers and real numbers in
expressions; for example, 1.2 + 3 evaluates to 4.2.
Integers
ColdFusion supports integers between -2,147,483,648 and 2,147,483,647 (32-bit signed
integers). You can assign a value outside this range to a variable, but ColdFusion initially stores
the number as a string. If you use it in an arithmetic expression, ColdFusion converts it into a
floating point value, preserving its value, but losing precision as the following example shows:
<cfset mybignum=12345678901234567890>
<cfset mybignumtimes10=(mybignum * 10)>
<cfoutput>mybignum is: #mybignum#</cfoutput><br>
<cfoutput>mybignumtimes10 is: #mybignumtimes10# </cfoutput><br>
This example generates the following output:
mybignum is: 12345678901234567890
mybignumtimes10 is: 1.23456020
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...