Components also have a Super keyword that is sometimes called a scope. For information on the Super keyword, see Using the Super keyword in Using CFCs effectively.
The This scope is available within the CFC and is shared by all CFC methods. It is also available in the base component (if the CFC is a child component), on the page that instantiates the CFC, and all CFML pages included by the CFC.
Inside the CFC, you define and access This scope variables by using the prefix This, as in the following line:
In the calling page, you can define and access CFC This scope variables by using the CFC instance name as the prefix. For example, if you create a CFC instance named car and, within the car CFC specify <cfset This.color="green">, a ColdFusion page that instantiates the CFC could refer to the component's color property as #car.color#.
Variable values in the This scope last as long as the CFC instance exists and, therefore, can persist between calls to methods of a CFC instance.
The Variables scope in a CFC is private to the CFC. It includes variables defined in the CFC body (initialization or constructor code) and in the CFC methods. When you set Variables scope variables in the CFC, they cannot be seen by pages that invoke the CFC.
The CFC Variables scope does not include any of the Variables scope variables that are declared or available in the page that instantiates or invokes the CFC. However, you can make the Variables scope of the page that invokes a CFC accessible to the CFC by passing Variables as an argument to the CFC method.
You set a Variables scope variable by assigning a value to a name that has the Variables prefix or no prefix.
Values in the Variables scope last as long as the CFC instance exists, and therefore can last between calls to CFC instance methods.
The Variables scope is available to included pages, and Variables scope variables that are declared in the included page are available in the component page.
The Variables scope is not the same as the function local scope, which makes variables private within a function. Always define function-local variables using the var keyword of the Local scope name.
The following example shows how to make the Variables scope of the page that invokes a CFC accessible to the CFC by passing Variables as an argument to the CFC method. It also illustrates that the Variables scope is private to the CFC.
The following code is for the callGreetMe.cfm page:
<cfset Variables.MyName="Wilson"> <cfobject component="greetMe" name="myGreetings"> <cfoutput> Before invoking the CFC, Variables.Myname is: #Variables.MyName#.<br> Passing Variables scope to hello method. It returns: #myGreetings.hello(Variables.MyName)#.<br> After invoking the CFC, Variables.Myname is: #Variables.MyName#.<br> </cfoutput> <cfinvoke component="greetMe" method="VarScopeInCfc">
<cfcomponent> <cfset Variables.MyName="Tuckerman"> <cffunction name="hello"> <cfargument name="Name" Required=true> <cfset Variables.MyName="Hello " & Arguments.Name> <cfreturn Variables.MyName> </cffunction> <cffunction name="VarScopeInCfc"> <cfoutput>Within the VarScopeInCfc method, Variables.MyName is: #variables.MyName#<br></cfoutput> </cffunction> </cfcomponent>
Before invoking the CFC, Variables.Myname is: Wilson. Passing Variables scope to hello method. It returns: Hello Wilson. After invoking the CFC, Variables.Myname is: Wilson. Within the VarScopeInCfc method, Variables.MyName is: Tuckerman
The Arguments scope exists only in a
- As named attributes to the cfinvoke tag
- In the cfargumentcollection attribute of the cfinvoke tag
- In cfinvokeargument tags
- As attributes or parameters passed into the method when the method is invoked as a web service, by Flash Remoting, as a direct URL, or by submitting a form
You can access variables in the Arguments scope using structure notation (Arguments.variablename), or array notation (Arguments or Arguments["
The Arguments scope does not persist between calls to CFC methods.
Variables in the Arguments scope are available to pages included by the method.
A CFC shares the Form, URL, Request, CGI, Cookie, Client, Session, Application, Server, and Flash scopes with the calling page. Variables in these scopes are also available to all pages that are included by a CFC. These variables do not have any behavior that is specific to CFCs.
Variables that you declare with the Var keyword inside a
Always use the Var keyword or Local scope name on variables that are only used inside the function in which they are declared.
Define all function local variables at the top of the function definition, before any other CFML code; for example:
<cffunction ...> <cfset Var testVariable = "this is a local variable"> <!--- Function code goes here. ---> <cfreturn myresult> </cffunction>
Any arguments declared with the cfargument tag must appear before any variables defined with the cfset tag. You can also place any cfscript tag first and define variables that you declare with the Var keyword in the script.
Use function local variables if you place the CFC in a persistent scope such as the Session scope, and the function has data that must be freed when the function exits.
Local variables do not persist between calls to CFC methods.
Local variables are available to pages included by the method.