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cfflush
DescriptionFlushes
currently available data to the client.
Syntax<cfflush
interval = "integer number of bytes">
Note: You can specify this tag’s attributes in an attributeCollection attribute
whose value is a structure. Specify the structure name in the attributeCollection attribute
and use the tag’s attribute names as structure keys.
Attributes
Attribute
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Req/Opt
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Default
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Description
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interval
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Optional
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Integer. Flushes output each time this number
of bytes becomes available. HTML headers, and data that is already
available when the tag is executed, are omitted from the count.
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UsageThe first
occurrence of this tag on a page sends back the HTML headers and
any other available HTML. Subsequent cfflush tags
on the page send only the output that was generated after the previous
flush.
When you flush data, ensure that enough information
is available, as some browsers might not respond if you flush only
a small amount. Similarly, set the interval attribute
for a few hundred bytes or more, but not thousands of bytes.
Use
the interval attribute only when a large amount
of output is sent to the client, such as in a cfloop or
a cfoutput of a large query. Using this form globally
(such as in the Application.cfm file) might cause unexpected errors when
CFML tags that modify HTML headers are executed.
Because
the cfflush tag sends data to the browser when
it executes, it has several limitations, including the following:
Using any of the following tags or functions on a page anywhere
after the cfflush tag can cause errors or unexpected
results: cfcontent, cfcookie,cfform, cfheader, cfhtmlhead, cflocation,
and SetLocale. Similarly, do not use any tags that
use AJAX features, including cfdiv, cflayout, cflayoutarea, cfpod, cfsprydataset, cftooltip, cfwindow,
or HTML format cfgrid, cftree, cftextarea, or cfinput (using autosuggest or datefield attributes)
tags. All of the preceding tags and functions normally modify the
HTML header, but cannot do so after a cfflush tag,
because the cfflush sends the header.
Using the cfset tag to set a cookie anywhere
on a page that has a cfflush tag does not set the
cookie in the browser.
Using the cfflush tag in the body of several
tags, including cfsavecontent, cfquery,
and custom tags, causes errors.
If you save Client variables as cookies, any client variables
that you set after a cfflush tag are not saved
in the browser.
Note: Normally, the cferror tag
discards the current output buffer and replaces it with the contents
of the error page. The cfflush tag discards the
current buffer. As a result, the Error.GeneratedContent variable
resulting from a cferror tag after a cfflush contains
any contents of the output buffer that has not been flushed. This
content is not sent to the client. The content of the error page
displays to the client after the bytes that have been sent.
ExampleThe
following example uses cfloop tags and the rand random
number generating function to delay data display. It simulates a
page that is slow to generate data.
<h1>Your Magic numbers</h1>
<p>It will take us a little while to calculate your ten magic numbers. It takes a lot of work to find numbers that truly fit your personality. So relax for a minute or so while we do the hard work for you.</p>
<H2>We are sure you will agree it was worth the short wait!</H2>
<cfflush>
<cfflush interval=10>
<!--- Delay Loop to make it seem harder. --->
<cfloop index="randomindex" from="1" to="200000" step="1">
<cfset random=rand()>
</cfloop>
<!--- Now slowly output 10 random numbers. --->
<cfloop index="Myindex" from="1" to="10" step="1">
<cfloop index="randomindex" from="1" to="100000" step="1">
<cfset random=rand()>
</cfloop>
<cfoutput>
Magic number #Myindex# is: #RandRange
100000, 999999)#<br><br>
</cfoutput>
</cfloop>
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