Defines an interface that consists of a set of signatures for functions. The interface does not include the full function definitions; instead, you implement the functions in a ColdFusion component (CFC). The interfaces that you define by using this tag can make up the structure of a reusable application framework.

ColdFusion 8: Added this tag.

Application framework tags ,  Extensibility tags

cfargument ,  cfcomponent ,  cffunction ,  GetComponentMetaData ,  IsInstanceOf

The cfinterface tag declares a set of related functions that any ColdFusion component (CFC) that implements the interface must define. The interface specifies function signatures, but does not implement the functions; instead, the CFC that implements the interface must contain the full function definitions. For example, you could create a create, read, update, and delete (CRUD) interface that defines the basic signatures of the four operations. All components that implement the interface must then conform to the interface signatures. You can then implement the interface in different components to manage different types of data sources. Because all the components implement the same interface, you can ensure that you can easily replace one component with another, depending on the specific data source that an individual application requires. You define an interface by creating a ColdFusion file with a .cfc extension and specifying the cfinterface tag as the first and only top-level tag in the file. The filename determines the interface name, so myInterface.cfc defines the myInterface interface. You can specify any attributes in the cfinterface tag; however, only the names listed in the Attributes table are meaningful to ColdFusion. The filename must not contain commas, or any periods except for the separator before the .cfc extension. Inside the cfinterface tag body, you specify the interface by declaring the functions of the interface. The interface definition must follow these basic rules:

This interface extends the IBasicInterface interface, so any component that implements this interface must also implement the methods of the IBasicInterface interface. This interface requires the component to implement the following three functions:

A CFC can implement multiple interfaces.

ColdFusion uses the same rules to locate interfaces as it does to locate components. You can use the  GetComponentMetaData  function to get information about an interface.Adobe recommends that you use a consistent technique for identifying interface names, for example, by always starting the file (and therefore interface) name with a capital I. Any component that implements only that single interface could have a similar name, for example the same root prefixed by a capital C. You could have an IresourceInfo.cfc interface file and a corresponding CresourceInfo.cfc component file, for example.

The following example defines an IBasicMath interface with add, subtract, multiply, and divide operations. The integerMath CFC implements this interface by defining integer arithmetic versions of the operations. The testMath.cfm application uses the integerMath functions to do arithmetic calculations on two decimal numbers (using the values of pi and e). As an exercise, consider modifying the interface definition to take and return values of any type, and then implement a second CFC that uses the PrecisionEvaluate function to calculate arbitrary precision arithmetic and return the results. (These versions are omitted for brevity.)The IBasicMath.cfc file defines the interface as follows:

The integerMath.cfc file defines the integerMath component, which implements the IBasicMath interface, as follows:

The testMath.cfm file uses the integerMath component methods to calculate integer values, as follows: