Object-Oriented Programming in ColdFusion: Break free from procedural programming and learn how to optimize your applications and enhance your skills using objects and design patterns

In Chapter 1, Introducing ColdFusion Components we looked at how to create an instance of a ColdFusion component using the createObject() function. We also looked at how to pass values through to the instantiated object upon creation using the init() method (also known as the object constructor method), thereby making them available to all methods within the CFC.

You can use any CFML tags or CFScript code within your component document to create your constructor code, and typically it is best practice to place the constructors at the top of the document, directly beneath the opening cfcomponent tag and before any method definitions.

ColdFusion provides an alternative method for setting your CFC-wide variables in your component, using a pseudo-constructor. This term simply refers to the code contained within the cfcomponent tags but outside of a cffunction block.

A pseudo-constructor's role is to set variables, run queries, or run any code during the instantiation of the...

ColdFusion components allow you to return the values of all allowed data types. The cfreturn tag, as we have seen in Chapter 1, and in the getCurrentDate() method in the projects.cfc code, returns a single variable. The return statement in CFScript also returns only one result at a time. If a requirement for the code was to send back more than one variable from the method, a structure or array could be returned containing all required variables and values.

When returning data from a method, you have the ability to explicitly specify what type of value is expected to be returned by using the returnType attribute.

Access attributes control the access to the methods within the component. At its simplest, the access attribute specifies who/what code can access the method and use its services.

Familiarizing yourself with the range of access attributes gives you greater freedom to code remotely using a web service and to integrate other web development tools, such as Flash and Flex, to use ColdFusion output.

It also helps to ensure that you do not restrict function access to a commonly used utility, or open up a method possibly containing private and confidential business logic or code to any third party.

The access attribute is placed within the cffunction tag as follows:

<cffunction name="getAllProjects" returnType="query" output="false" access="public">
</cffunction>

Listing 2.6 Using the access attribute

There are four options to choose from when using this attribute, and all four have a different level of access assigned to them.

ColdFusion components have the unique ability to look within themselves and display information regarding their content. It can display all of the methods contained within the component, all of the properties within the functions, including parameters and arguments, and what, if any, information is to be returned. This is commonly referred to as introspection.

From the minimal effort of adding extra hint and displayname tags, the output generated by the CFC Explorer tool for introspection has been enhanced to display much more detail pertaining to the component and its properties.

In a shared working environment, this would be of great benefit to all developers wishing to collaborate on a project and the CFC resources used within.

In this chapter, we have discussed the benefits of including additional attributes to your components and their included properties and methods to improve on documentation.

Other topics that we have covered in this chapter are: