MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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Data types 55
Variable characteristics
You can classify a variable using the following characteristics:
•
The data type of the variable value, which indicates the kind of information a variable
represents, such as number, string, or date
•
The scope of the variable, which indicates where the information is available and how long the
variable persists
The following sections provide detailed information on Data types and scopes.
Data types
ColdFusion is often referred to as typeless because you do not assign types to variables and
ColdFusion does not associate a type with the variable name. However, the data that a variable
represents does have a type, and the data type affects how ColdFusion evaluates an expression or
function argument. ColdFusion can automatically convert many data types into others when it
evaluates expressions. For simple data, such as numbers and strings, the data type is unimportant
until the variable is used in an expression or as a function argument.
ColdFusion variable data belongs to one of the following type categories:
•
Simple One value. Can use directly in ColdFusion expressions. Include numbers, strings,
Boolean values, and date-time values.
•
Complex A container for data. Generally represent more than one value. ColdFusion built-
in complex data types include arrays, structures, queries, and XML document objects.
You cannot use a complex variable, such as an array, directly in a ColdFusion expression, but
you can use simple data type elements of a complex variable in an expression.
For example, with a one-dimensional array of numbers called myArray, you cannot use the
expression myArray * 5. However, you could use an expression myArray[3] * 5 to multiply the
third element in the array by five.
•
Binary
Raw data, such as the contents of a GIF file or an executable program file.
•
Objects
Complex constructs. Often encapsulate both data and functional operations. The
following table lists the types of objects that ColdFusion can use, and identifies the chapters
that describe how to use them:
Object type See
Component Object Model (COM) Chapter 34, “Integrating COM and CORBA Objects in CFML
Applications,” on page 761
Common Object Request Broker
Architecture (CORBA) Chapter 34, “Integrating COM and CORBA Objects in CFML
Applications,” on page 761
Java Chapter 33, “Integrating J2EE and Java Elements in CFML
Applications,” on page 735
ColdFusion component Chapter 11, “Building and Using ColdFusion Components,”
on page 219
Web service Chapter 32, “Using Web Services,” on page 707