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 |b|
  b.use A
  b.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 either yield the builder or be evaluated in the context of the instance.

Example:

Builder.new do |b|
  b.use A
  b.use B
end

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 41

def initialize(opts = nil, &block)
  opts ||= {}
  @runner_class = opts[:runner_class] || Runner
  @middleware_name = opts[:name] || 'Middleware'

  if block_given?
    if block.arity == 1
      yield self
    else
      instance_eval(&block)
    end
  end
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 135

def call(env = nil)
  to_app.call(env)
end

#delete(index) ⇒ Object

Deletes the given middleware object or index



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# File 'lib/middleware/builder.rb', line 129

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 63

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

#inject_logger(logger) ⇒ Object 



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# File 'lib/middleware/builder.rb', line 147

def inject_logger logger
  insert_before_each Middleware::Logger, logger, name

  self
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 87

def insert(index, middleware, *args, &block)
  index = self.index(index) unless index.is_a?(Integer)
  fail "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 96

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

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

Inserts a middleware after each middleware object



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# File 'lib/middleware/builder.rb', line 110

def insert_after_each(middleware, *args, &block)
  self.stack = stack.reduce([]) do |carry, item|
    carry.push(item, [middleware, args, block])
  end
end

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

Inserts a middleware before each middleware object



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

def insert_before_each(middleware, *args, &block)
  self.stack = stack.reduce([]) do |carry, item|
    carry.push([middleware, args, block], item)
  end
end

#inspect ⇒ Object 



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# File 'lib/middleware/builder.rb', line 139

def inspect
  name+'[' + stack.reduce([]) do |carry, middleware|
    name = middleware[0].is_a?(Proc) ? 'Proc' : middleware[0].name

    carry << "#{name}(#{middleware[1].join(', ')})"
  end.join(', ') + ']'
end

#name ⇒ Object

Returns the name of the current middleware



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

def name
  @middleware_name
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 118

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 74

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

  self
end