Web Oriented Object Framework

User Guide (Version 0.5b4)

Woof!
User Guide (Version 0.5b4)

Table of Contents
Implementing controllers The request object

Implementing actions

Exposing controller methods as actions

By default, all methods exported by a controller class are accessible through a URL. Note this refers to the leaf controller class exports and not any methods it inherits. Without an explicit export statement, exports all methods beginning with a lower case letters and no others. Alternatively, you can use the Tcl class definition commands export and unexport to control what methods are exported.

However, using Tcl's built-in mechanisms has the problem that un-exporting a method to prevent being accessed from a URL as an action also prevents it from being called by other objects. Woof! provides another mechanism for controlling exposure of methods as actions. A controller can define the method _action_methods. This should return a list of method names that may be accessed as actions. If this list is empty, the default behaviour above, where all exported methods are treated as actions, results.

Defining an action method

As shown below, an action method may be defined within the class definition or outside it:

oo::class create SampleController {
    superclass ApplicationController
    constructor args {
        # Very important to pass arguments to parent
        next {*}$args

        ...other initialization code...

    }

    method index {} {
        # The default method for the controller
        ...some code here...
    }
}

oo::define SampleController {
    method another_method {} {
        ...whatever...
    }

    method one_more_method {} {
        ...whatever...
    }

}

There is no real difference between the two styles, though the first may be very marginally faster if a large number of methods are defined.

Action method parameters

An action method may retrieve query parameters sent by the client in one of two ways shown in the following two definitions:

Both methods are shown below.

oo::define Sample {
   method m1 {} {
      set p1 [params get p1]
      set p2 [params get p2]
      ...do something with p1 and p2...
   }

   method m2 {p1 p2} {
      ...do something with p1 and p2...
   }
}

In the second case, Woof! will send an error to the client if its request does not contain parameters p1 and p2. This could be avoided by the standard Tcl default value mechanism for method arguments. Note that the method may still retrieve additional parameters from the params object as appropriate.

If the method has a variable number of parameters, as indicated by a trailing args parameter, Woof! will append all additional query parameters (ie. those not defined as method parameters) to the method call as alternating parameter name and value pairs.

Defining a missing action handler

When Woof! does not find a controller method with the name specified for the action, it invokes the method _missing_action on the class. The default implementation of this in class Controller generates a Page not found. error page.

A controller may usefully override this method. For example, the controller for this user guide defines this method to simply return. The consequence is that Woof! will then simply pick up and display the appropriate page template for the documentation sections as specified by the action. No separate action method needs to be defined for each section.

Implementing controllers The request object