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You can ensure that a variable exists by using the cfparam
tag, which tests for the variables existence and optionally supplies a default value if the variable does not exist. The cfparam
tag has the following syntax:
<cfparam name="VariableName
" type="data_type
" default="DefaultValue
">
Note: For information on using the type
attribute to validate the parameter data type, see CFML Reference.
There are two ways to use the cfparam
tag to test for variable existence, depending on how you want the validation test to proceed:
name
attribute to test that a required variable exists. If it does not exist, the ColdFusion server stops processing the page and displays an error message. name
and default
attributes to test for the existence of an optional variable. If the variable exists, processing continues and the value is not changed. If the variable does not exist, it is created and set to the value of the default
attribute, and processing continues.The following example shows how to use the cfparam
tag to check for the existence of an optional variable and to set a default value if the variable does not already exist:
<cfparam name="Form.Contract" default
="Yes">
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