Class: Middleware::Builder

Inherits:
Object
  • Object
show all
Defined in:
lib/middleware/builder.rb

Overview

This provides a DSL for building up a stack of middlewares.

This code is based heavily off of Rack::Builder and ActionDispatch::MiddlewareStack in Rack and Rails, respectively.

Usage

Building a middleware stack is very easy:

app = Middleware::Builder.new do
  use A
  use B
end

# Call the middleware
app.call(7)

Instance Method Summary collapse

Constructor Details

#initialize(opts = nil) { ... } ⇒ Builder

Initializes the builder. An optional block can be passed which will be evaluated in the context of the instance.

Example:

Builder.new do
  use A
  use B
end

Parameters:

  • opts (Hash) (defaults to: nil) —

    Options hash

Options Hash (opts):

  • :runner_class (Class) —

    The class to wrap the middleware stack in which knows how to run them.

Yields:

  • [] Evaluated in this instance which allows you to use methods like #use and such.



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# File 'lib/middleware/builder.rb', line 35

def initialize(opts=nil, &block)
  opts ||= {}
  @runner_class   = opts[:runner_class] || Runner
  @reuse_instance = opts[:reuse_instance]
  instance_eval(&block) if block_given?
end

Instance Method Details

#call(env = nil) ⇒ Object

Runs the builder stack with the given environment.



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# File 'lib/middleware/builder.rb', line 103

def call(env=nil)
  if @reuse_instance
    runner_instance.call(env)
  else
    to_app.call(env)
  end
end

#delete(index) ⇒ Object

Deletes the given middleware object or index



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# File 'lib/middleware/builder.rb', line 97

def delete(index)
  index = self.index(index) unless index.is_a?(Integer)
  stack.delete_at(index)
end

#flatten ⇒ Object

Returns a mergeable version of the builder. If use is called with the return value of this method, then the stack will merge, instead of being treated as a separate single middleware.



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# File 'lib/middleware/builder.rb', line 45

def flatten
  lambda do |env|
    self.call(env)
  end
end

#insert(index, middleware, *args, &block) ⇒ Object Also known as: insert_before

Inserts a middleware at the given index or directly before the given middleware object.



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# File 'lib/middleware/builder.rb', line 69

def insert(index, middleware, *args, &block)
  index = self.index(index) unless index.is_a?(Integer)
  raise "no such middleware to insert before: #{index.inspect}" unless index
  stack.insert(index, [middleware, args, block])
end

#insert_after(index, middleware, *args, &block) ⇒ Object

Inserts a middleware after the given index or middleware object.



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# File 'lib/middleware/builder.rb', line 78

def insert_after(index, middleware, *args, &block)
  index = self.index(index) unless index.is_a?(Integer)
  raise "no such middleware to insert after: #{index.inspect}" unless index
  insert(index + 1, middleware, *args, &block)
end

#replace(index, middleware, *args, &block) ⇒ Object

Replaces the given middleware object or index with the new middleware.



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# File 'lib/middleware/builder.rb', line 86

def replace(index, middleware, *args, &block)
  if index.is_a?(Integer)
    delete(index)
    insert(index, middleware, *args, &block)
  else
    insert_before(index, middleware, *args, &block)
    delete(index)
  end
end

#use(middleware, *args, &block) ⇒ Object

Adds a middleware class to the middleware stack. Any additional args and a block, if given, are saved and passed to the initializer of the middleware.

Parameters:

  • middleware (Class) —

    The middleware class



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# File 'lib/middleware/builder.rb', line 56

def use(middleware, *args, &block)
  if middleware.kind_of?(Builder)
    # Merge in the other builder's stack into our own
    self.stack.concat(middleware.stack)
  else
    self.stack << [middleware, args, block]
  end

  self
end