Creating a Component (.cfc)

A CFC is a single .cfm-like file, saved with a .cfc extension, whose entire contents are wrapped in a component definition. Nothing lives outside it — no loose code before or after.

Learning Objectives

After completing this lesson, you'll be able to:

Write a CFC in both CFScript (component) and tag (<cfcomponent>) syntax.
Use the key attributes: extends, implements, accessors, output.
Know the basic file rules a .cfc has to follow.

CFScript: the component Keyword

CFScript — User.cfc

component accessors="true" {

    property name="name" type="string";
    property name="age" type="numeric";

    function init(required string name, numeric age = 0) {
        variables.name = arguments.name;
        variables.age = arguments.age;
        return this;
    }

}

Tag Syntax: <cfcomponent>

Tag Syntax — User.cfc

<cfcomponent accessors="true">

    <cfproperty name="name" type="string">
    <cfproperty name="age" type="numeric">

    <cffunction name="init" returnType="User">
        <cfargument name="name" type="string" required="true">
        <cfargument name="age" type="numeric" required="false" default="0">
        <cfset variables.name = arguments.name>
        <cfset variables.age = arguments.age>
        <cfreturn this>
    </cffunction>

</cfcomponent>

Key cfcomponent / component Attributes

Attribute	Purpose
extends	Name of a parent component to inherit methods and properties from
implements	One or more interfaces this component must satisfy (comma-delimited for multiple)
accessors	Whether ColdFusion auto-generates getX()/setX() methods for declared properties (default true)
output	Whether the component's pseudo-constructor code (outside any function) can produce HTML output
persistent	Marks the CFC persistent for Hibernate ORM use
hint / displayname	Documentation shown when introspecting the component

File Rules

The file extension must be .cfc, and the filename becomes the component's default name when instantiated.
The entire file must be wrapped in the component definition — no code allowed outside it.
Everything between the opening brace/tag and the first function runs automatically on instantiation — this is the pseudo-constructor, covered in the Constructor lesson.

Common Beginner Mistakes

Writing code outside the component block

A .cfc file's entire content has to live inside the component { } (or <cfcomponent></cfcomponent>) definition — anything else is a syntax error.

Forgetting accessors="true" and then calling a getter/setter that doesn't exist

Auto-generated getX()/setX() methods only exist when accessors is enabled (it defaults to true in modern CFML, but older code sometimes turns it off) — check the component's attribute if a getter call fails unexpectedly.

Best Practices

Name the CFC file to match what it represents (User.cfc, OrderService.cfc) — the filename is the component's default name everywhere it's referenced.
Declare property types explicitly — it documents intent and helps catch mistakes when accessors generate getters/setters.

Interview Questions

What does the implements attribute do on a component?

It declares one or more interfaces the component must satisfy — every method signature in the listed interface(s) must be implemented, or ColdFusion raises an error.

What determines a CFC's default component name?

The filename, minus the .cfc extension — User.cfc becomes User when instantiated with new User().

Summary

In this lesson, you covered the component / <cfcomponent> syntax, the key attributes (extends, implements, accessors, output), and the basic rules a .cfc file has to follow.

What's Next?

The next lesson covers actually creating objects from a CFC — new vs createObject(), and what an instance actually is at runtime.

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