Difference between revisions of "Getting Started with CFML in ColdFusion and Railo"

Revision as of 23:11, 29 August 2014

CFML is the programming language used to create applications in ColdFusion and Railo, and it traditionally uses a tag-based syntax to perform tasks. Those who wish to avoid using tags also have the option of programming in the language's script-based alternative, CFScript. Below we'll cover some of the basics you'll need to master to build an application (Web site) using CFML.

Setting Variables

You can create/update variables using the cfset tag: <cfset foo = "bar">

In CFScript you just type the variable name and assign it a value: <cfscript> foo = "bar"; </cfscript>

Displaying Contents of Variables

If you wish to display a variable on a page (send the variable's contents to the page-output stream), you can either use the CFOutput tag:

	<cfset foo = "bar">
	<cfoutput>#foo#</cfoutput>

Or in CFScript you can make use of the WriteOutput() and Echo() functions:

	<cfscript>
		set foo = "bar";
		set thud = "plug"
 
		WriteOutput("The value of foo is " & #foo#);
		Echo("The value of thud is " & #thud#);
	</cfscript>

Conditional Statements

The CFIf, CFElseIf, and CFElse tags allow you to create conditional statements for flow-control:

	<cfparam name = "Role" type = "string" default = "Guest">
 
	<cfif Role EQ "Author">
		<cfset AllowedToPost = true >
		<cfoutput>Welcome #UserName#! Feel free to add new content.</cfoutput>
	<cfelseif Role EQ "Reader">
		<cfset AllowedToPost = false>
		<cfoutput>Hello #UserName#, glad you're back.
	<cfelse>
		<cfoutput>Please log in to read articles or author new posts.</cfoutput>
	</cfif>

In CFScript you would make use of the if and else keywords. Combine them as else if to form the equivalent of CFElseIf:

	<cfscript>
		param name = "Role" type = "string" default = "Guest";
 
		if (Role EQ "Author")
		{
			AllowedToPost = true;
			echo("Welcome " & #UserName# & "! Feel free to add new content.");
		}
		else if (Role EQ "Reader")
		{
			AllowedToPost = false;
			echo("Hello " & #UserName# & "! Enjoy your reading.");
		}
		else
		{
			echo("Please log in to read articles or author new posts.);
		}
	</cfscript>

Note about CFParam: The CFParam tag checks that a variable is defined, validates the data if it is defined, and allows you to specify a default value if the variable is not defined. More info on the tag is available here:

• ColdFusion Documentation - CFParam
• Railo Documentation - CFParam

Loops

With the CFLoop tag, you can create an index-based loop, a conditional loop, or a loop to iterate over queries, lists, and arrays. For example, this will create a basic loop that prints the numbers 1-10 on new lines:

	<cfloop index = "i" from = "1" to = "10" step = "1">
		<cfoutput>#i#<br></cfoutput>
	</cfloop>

In CFScript, just use the loop keyword, followed by the attributes, and contain the statement(s) to be executed within braces:

	<cfscript>
		loop index = "i" from = "1" to = "10" step = "1"
		{
			echo(#i# & "<br>");
		}
	</cfscript>

More CFLoop Examples:

• ColdFusion Documenation - CFLoop
• Railo Documentation - CFLoop

Accessing Databases with CFQuery

To interact with databases, first define a ColdFusion datasource (DSN) in your control panel or in your Application.cfc (Railo 4.1+ and CF 11+). Once you have a working datasource, you can use the CFQuery tag to run SQL queries against your database server:

	<cfquery name = "customers" datasource = "MyDSN">
		SELECT firstname, lastname, phone
		FROM contacts
		WHERE customer IS TRUE;
	</cfquery>

In CFScript:

	customers = new Query(datasource = "MyDSN", sql = "SELECT firstname, lastname, phone FROM contacts WHERE customer IS TRUE;").execute().getResult();

CFQuery References:

• ColdFusion Documentation - CFQuery
• Railo Documentation - CFQuery
• Dave Ferguson's Blog - CFScript Query Examples

Further Reading

• Learn CF In A Week
• Try ColdFusion
• ColdFusion CFScript Documentation
• Railo - Tags in CFScript
• CFScript Cheat Sheet