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201
DEVELOPING
COLDFUSION 9 APPLICATIONS
Building Blocks of ColdFusion Applications
Las
t
upda
te
d 8/5/2010
Using CFCs effectively
Several techniques let you effectively use CFCs in your applications:
•
Structure and reuse code
•
Build secure CFCs
•
Use introspection to get information about components
Structuring and reusing code
Component inheritance and the Super keyword are two important tools for creating structured, object-oriented
ColdFusion components.
Component inheritance
Lets you create a single base component and reuse this code in multiple subclasses that are
derived from the base component. Typically a base component is more general, and subcomponents are typically more
specific. Each subclass does not have to redefine the code in the base component, but can override it if necessary.
The Super keyword
Lets a component that overrides a base component method execute the original base component
method. This technique lets your subclassed component override a method without losing the ability to call the
original version of the method.
Using component inheritance
Component inheritance lets you import component methods and properties from one component to another
component. Inherited components share any component methods or properties that they inherit from other
components, and ColdFusion initializes instance data in the parent CFC when you instantiate the CFC that extends it.
Component inheritance defines an
is a
relationship between components. For example, a component named
president.cfc inherits its methods and properties from manager.cfc, which inherits its methods and properties from
employee.cfc. In other words, president.cfc
is a
manager.cfc; manager.cfc
is an
employee.cfc; and president.cfc
is an
employee.cfc.
In this example, employee.cfc is the
base
component; it’s the component upon which the others are based. The
manager component extends the employee component; it has all the methods and properties of the employee
component, and some additional ones. The president component extends the manager component. The president
component is called a subcomponent or child component of the manager component, which, in turn, is a child
component of the employee component.
1
Create the employee.cfc file with the following content:
<cfcomponent>
<cfset This.basesalary=40*20>
</cfcomponent>
2
Create the manager.cfc file with the following content:
<cfcomponent extends="employee">
<cfset This.mgrBonus=40*10>
</cfcomponent>
In the example, the cfcomponent tag’s
extends
attribute points to the
employee
component.
3
Create the president.cfc file with the following content:
<cfcomponent extends="manager">
<cfset This.prezBonus=40*20>
</cfcomponent>
In the example, the cfcomponent tag’s
extends
attribute points to the
manager
component.
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