Class: Middlegem::Definition Abstract

Inherits:
Object
  • Object
show all
Defined in:
lib/middlegem/definition.rb

Overview

This class is abstract.

Definition is an abstract class whose implementations are capable of defining what middlewares are permitted in a given context and in what order they should be executed. Note that this concept of “middleware definitions” is a major difference from other middleware solutions, where middlewares are simply inserted into a stack. In middlegem, a Definition determines what order the middleware in a Stack should be called. This greatly decreases the likelihood of “middleware conflicts”, where one middleware expects another to have already run. The downside, of course, is the verbosity—all middleware must be defined.

It should be noted, however, that the concept of a “middleware definition” is completely flexible. If you would prefer to simply insert middlewares into a stack without defining them, you can create a Definition implentation whose #sort method just returns the unsorted middlewares. And if you want to allow any middlewares to be inserted, simply return true from the #defined? method. On the other hand, there is a lot of flexibility in how you determine the middleware order: define a DSL, let middleware have dependencies, define middleware “groups”, allow middleware “priorities”—the possibilities are endless!

Currently, the only default implementation is ArrayDefinition, which executes middleware based on an ordered list of middleware classes.

Finally, you might notice that Definition contains no actual instance method implementations. In other words, for all intents and pruposes, it is empty! This is intentional. A middleware definition is any object that implements both a #defined? and a #sort method (see Definition.valid?). You may extend this class, however, to explicitly mark your middleware definition classes as middleware definitions.

Author:

  • Jacob Lockard

Since:

  • 0.1.0

Direct Known Subclasses

ArrayDefinition

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.valid?(definition) ⇒ bool

Determines whether the given object is a valid middleware definition. Currently, any object that implements a defined? method and a sort method is valid.

Parameters:

  • definition (Object) —

    the middleware definition to check.

Returns:

  • (bool) —

    whether the given object is a valid middleware definition.

Since:

  • 0.1.0



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# File 'lib/middlegem/definition.rb', line 38

def self.valid?(definition)
  definition.respond_to?(:defined?) && definition.respond_to?(:sort)
end

Instance Method Details

#defined?(middleware) ⇒ bool

Should determine whether the given middleware is defined according to this Middlegem::Definition. Feel free to determine this however you like! This method will be used to validate middlewares added to a Stack.

Parameters:

  • middleware (Object) —

    the middleware object to check.

Returns:

  • (bool) —

    whether the given middleware object is defined.




# File 'lib/middlegem/definition.rb', line 42

#sort(middlewares) ⇒ Array<Object>

Should sort the given array of middlewares according to this Middlegem::Definition. In a Stack, middlewares will be called in the order returned.

Parameters:

  • middlewares (Array<Object>) —

    the middlewares to sort.

Returns:

  • (Array<Object>) —

    the sorted middlewares.




# File 'lib/middlegem/definition.rb', line 49